Add 'protobuf' library to project

Library is configured to compile as 'lite'.

1 files changed, 8336 insertions, 0 deletions

diff --git a/NorthstarDedicatedTest/include/protobuf/descriptor_unittest.cc b/NorthstarDedicatedTest/include/protobuf/descriptor_unittest.cc
new file mode 100644
index 00000000..be94e972
--- /dev/null
+++ b/NorthstarDedicatedTest/include/protobuf/descriptor_unittest.cc
@@ -0,0 +1,8336 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: kenton@google.com (Kenton Varda)
+//  Based on original Protocol Buffers design by
+//  Sanjay Ghemawat, Jeff Dean, and others.
+//
+// This file makes extensive use of RFC 3092.  :)
+
+#include <limits>
+#include <memory>
+#include <vector>
+
+#include <any.pb.h>
+#include <compiler/importer.h>
+#include <compiler/parser.h>
+#include <unittest.pb.h>
+#include <unittest_custom_options.pb.h>
+#include <stubs/common.h>
+#include <stubs/logging.h>
+#include <stubs/stringprintf.h>
+#include <unittest_lazy_dependencies.pb.h>
+#include <unittest_proto3_arena.pb.h>
+#include <io/tokenizer.h>
+#include <io/zero_copy_stream_impl.h>
+#include <descriptor.pb.h>
+#include <descriptor.h>
+#include <descriptor_database.h>
+#include <dynamic_message.h>
+#include <text_format.h>
+#include <stubs/strutil.h>
+#include <gmock/gmock.h>
+#include <testing/googletest.h>
+#include <gtest/gtest.h>
+#include <stubs/logging.h>
+#include <stubs/substitute.h>
+
+
+#include <port_def.inc>
+
+namespace google {
+namespace protobuf {
+
+// Can't use an anonymous namespace here due to brokenness of Tru64 compiler.
+namespace descriptor_unittest {
+
+// Some helpers to make assembling descriptors faster.
+DescriptorProto* AddMessage(FileDescriptorProto* file,
+                            const std::string& name) {
+  DescriptorProto* result = file->add_message_type();
+  result->set_name(name);
+  return result;
+}
+
+DescriptorProto* AddNestedMessage(DescriptorProto* parent,
+                                  const std::string& name) {
+  DescriptorProto* result = parent->add_nested_type();
+  result->set_name(name);
+  return result;
+}
+
+EnumDescriptorProto* AddEnum(FileDescriptorProto* file,
+                             const std::string& name) {
+  EnumDescriptorProto* result = file->add_enum_type();
+  result->set_name(name);
+  return result;
+}
+
+EnumDescriptorProto* AddNestedEnum(DescriptorProto* parent,
+                                   const std::string& name) {
+  EnumDescriptorProto* result = parent->add_enum_type();
+  result->set_name(name);
+  return result;
+}
+
+ServiceDescriptorProto* AddService(FileDescriptorProto* file,
+                                   const std::string& name) {
+  ServiceDescriptorProto* result = file->add_service();
+  result->set_name(name);
+  return result;
+}
+
+FieldDescriptorProto* AddField(DescriptorProto* parent, const std::string& name,
+                               int number, FieldDescriptorProto::Label label,
+                               FieldDescriptorProto::Type type) {
+  FieldDescriptorProto* result = parent->add_field();
+  result->set_name(name);
+  result->set_number(number);
+  result->set_label(label);
+  result->set_type(type);
+  return result;
+}
+
+FieldDescriptorProto* AddExtension(FileDescriptorProto* file,
+                                   const std::string& extendee,
+                                   const std::string& name, int number,
+                                   FieldDescriptorProto::Label label,
+                                   FieldDescriptorProto::Type type) {
+  FieldDescriptorProto* result = file->add_extension();
+  result->set_name(name);
+  result->set_number(number);
+  result->set_label(label);
+  result->set_type(type);
+  result->set_extendee(extendee);
+  return result;
+}
+
+FieldDescriptorProto* AddNestedExtension(DescriptorProto* parent,
+                                         const std::string& extendee,
+                                         const std::string& name, int number,
+                                         FieldDescriptorProto::Label label,
+                                         FieldDescriptorProto::Type type) {
+  FieldDescriptorProto* result = parent->add_extension();
+  result->set_name(name);
+  result->set_number(number);
+  result->set_label(label);
+  result->set_type(type);
+  result->set_extendee(extendee);
+  return result;
+}
+
+DescriptorProto::ExtensionRange* AddExtensionRange(DescriptorProto* parent,
+                                                   int start, int end) {
+  DescriptorProto::ExtensionRange* result = parent->add_extension_range();
+  result->set_start(start);
+  result->set_end(end);
+  return result;
+}
+
+DescriptorProto::ReservedRange* AddReservedRange(DescriptorProto* parent,
+                                                 int start, int end) {
+  DescriptorProto::ReservedRange* result = parent->add_reserved_range();
+  result->set_start(start);
+  result->set_end(end);
+  return result;
+}
+
+EnumDescriptorProto::EnumReservedRange* AddReservedRange(
+    EnumDescriptorProto* parent, int start, int end) {
+  EnumDescriptorProto::EnumReservedRange* result = parent->add_reserved_range();
+  result->set_start(start);
+  result->set_end(end);
+  return result;
+}
+
+EnumValueDescriptorProto* AddEnumValue(EnumDescriptorProto* enum_proto,
+                                       const std::string& name, int number) {
+  EnumValueDescriptorProto* result = enum_proto->add_value();
+  result->set_name(name);
+  result->set_number(number);
+  return result;
+}
+
+MethodDescriptorProto* AddMethod(ServiceDescriptorProto* service,
+                                 const std::string& name,
+                                 const std::string& input_type,
+                                 const std::string& output_type) {
+  MethodDescriptorProto* result = service->add_method();
+  result->set_name(name);
+  result->set_input_type(input_type);
+  result->set_output_type(output_type);
+  return result;
+}
+
+// Empty enums technically aren't allowed.  We need to insert a dummy value
+// into them.
+void AddEmptyEnum(FileDescriptorProto* file, const std::string& name) {
+  AddEnumValue(AddEnum(file, name), name + "_DUMMY", 1);
+}
+
+class MockErrorCollector : public DescriptorPool::ErrorCollector {
+ public:
+  MockErrorCollector() {}
+  ~MockErrorCollector() {}
+
+  std::string text_;
+  std::string warning_text_;
+
+  // implements ErrorCollector ---------------------------------------
+  void AddError(const std::string& filename, const std::string& element_name,
+                const Message* descriptor, ErrorLocation location,
+                const std::string& message) override {
+    const char* location_name = nullptr;
+    switch (location) {
+      case NAME:
+        location_name = "NAME";
+        break;
+      case NUMBER:
+        location_name = "NUMBER";
+        break;
+      case TYPE:
+        location_name = "TYPE";
+        break;
+      case EXTENDEE:
+        location_name = "EXTENDEE";
+        break;
+      case DEFAULT_VALUE:
+        location_name = "DEFAULT_VALUE";
+        break;
+      case OPTION_NAME:
+        location_name = "OPTION_NAME";
+        break;
+      case OPTION_VALUE:
+        location_name = "OPTION_VALUE";
+        break;
+      case INPUT_TYPE:
+        location_name = "INPUT_TYPE";
+        break;
+      case OUTPUT_TYPE:
+        location_name = "OUTPUT_TYPE";
+        break;
+      case IMPORT:
+        location_name = "IMPORT";
+        break;
+      case OTHER:
+        location_name = "OTHER";
+        break;
+    }
+
+    strings::SubstituteAndAppend(&text_, "$0: $1: $2: $3\n", filename,
+                              element_name, location_name, message);
+  }
+
+  // implements ErrorCollector ---------------------------------------
+  void AddWarning(const std::string& filename, const std::string& element_name,
+                  const Message* descriptor, ErrorLocation location,
+                  const std::string& message) override {
+    const char* location_name = nullptr;
+    switch (location) {
+      case NAME:
+        location_name = "NAME";
+        break;
+      case NUMBER:
+        location_name = "NUMBER";
+        break;
+      case TYPE:
+        location_name = "TYPE";
+        break;
+      case EXTENDEE:
+        location_name = "EXTENDEE";
+        break;
+      case DEFAULT_VALUE:
+        location_name = "DEFAULT_VALUE";
+        break;
+      case OPTION_NAME:
+        location_name = "OPTION_NAME";
+        break;
+      case OPTION_VALUE:
+        location_name = "OPTION_VALUE";
+        break;
+      case INPUT_TYPE:
+        location_name = "INPUT_TYPE";
+        break;
+      case OUTPUT_TYPE:
+        location_name = "OUTPUT_TYPE";
+        break;
+      case IMPORT:
+        location_name = "IMPORT";
+        break;
+      case OTHER:
+        location_name = "OTHER";
+        break;
+    }
+
+    strings::SubstituteAndAppend(&warning_text_, "$0: $1: $2: $3\n", filename,
+                              element_name, location_name, message);
+  }
+};
+
+// ===================================================================
+
+// Test simple files.
+class FileDescriptorTest : public testing::Test {
+ protected:
+  void SetUp() override {
+    // Build descriptors for the following definitions:
+    //
+    //   // in "foo.proto"
+    //   message FooMessage { extensions 1; }
+    //   enum FooEnum {FOO_ENUM_VALUE = 1;}
+    //   service FooService {}
+    //   extend FooMessage { optional int32 foo_extension = 1; }
+    //
+    //   // in "bar.proto"
+    //   package bar_package;
+    //   message BarMessage { extensions 1; }
+    //   enum BarEnum {BAR_ENUM_VALUE = 1;}
+    //   service BarService {}
+    //   extend BarMessage { optional int32 bar_extension = 1; }
+    //
+    // Also, we have an empty file "baz.proto".  This file's purpose is to
+    // make sure that even though it has the same package as foo.proto,
+    // searching it for members of foo.proto won't work.
+
+    FileDescriptorProto foo_file;
+    foo_file.set_name("foo.proto");
+    AddExtensionRange(AddMessage(&foo_file, "FooMessage"), 1, 2);
+    AddEnumValue(AddEnum(&foo_file, "FooEnum"), "FOO_ENUM_VALUE", 1);
+    AddService(&foo_file, "FooService");
+    AddExtension(&foo_file, "FooMessage", "foo_extension", 1,
+                 FieldDescriptorProto::LABEL_OPTIONAL,
+                 FieldDescriptorProto::TYPE_INT32);
+
+    FileDescriptorProto bar_file;
+    bar_file.set_name("bar.proto");
+    bar_file.set_package("bar_package");
+    bar_file.add_dependency("foo.proto");
+    AddExtensionRange(AddMessage(&bar_file, "BarMessage"), 1, 2);
+    AddEnumValue(AddEnum(&bar_file, "BarEnum"), "BAR_ENUM_VALUE", 1);
+    AddService(&bar_file, "BarService");
+    AddExtension(&bar_file, "bar_package.BarMessage", "bar_extension", 1,
+                 FieldDescriptorProto::LABEL_OPTIONAL,
+                 FieldDescriptorProto::TYPE_INT32);
+
+    FileDescriptorProto baz_file;
+    baz_file.set_name("baz.proto");
+
+    // Build the descriptors and get the pointers.
+    foo_file_ = pool_.BuildFile(foo_file);
+    ASSERT_TRUE(foo_file_ != nullptr);
+
+    bar_file_ = pool_.BuildFile(bar_file);
+    ASSERT_TRUE(bar_file_ != nullptr);
+
+    baz_file_ = pool_.BuildFile(baz_file);
+    ASSERT_TRUE(baz_file_ != nullptr);
+
+    ASSERT_EQ(1, foo_file_->message_type_count());
+    foo_message_ = foo_file_->message_type(0);
+    ASSERT_EQ(1, foo_file_->enum_type_count());
+    foo_enum_ = foo_file_->enum_type(0);
+    ASSERT_EQ(1, foo_enum_->value_count());
+    foo_enum_value_ = foo_enum_->value(0);
+    ASSERT_EQ(1, foo_file_->service_count());
+    foo_service_ = foo_file_->service(0);
+    ASSERT_EQ(1, foo_file_->extension_count());
+    foo_extension_ = foo_file_->extension(0);
+
+    ASSERT_EQ(1, bar_file_->message_type_count());
+    bar_message_ = bar_file_->message_type(0);
+    ASSERT_EQ(1, bar_file_->enum_type_count());
+    bar_enum_ = bar_file_->enum_type(0);
+    ASSERT_EQ(1, bar_enum_->value_count());
+    bar_enum_value_ = bar_enum_->value(0);
+    ASSERT_EQ(1, bar_file_->service_count());
+    bar_service_ = bar_file_->service(0);
+    ASSERT_EQ(1, bar_file_->extension_count());
+    bar_extension_ = bar_file_->extension(0);
+  }
+
+  DescriptorPool pool_;
+
+  const FileDescriptor* foo_file_;
+  const FileDescriptor* bar_file_;
+  const FileDescriptor* baz_file_;
+
+  const Descriptor* foo_message_;
+  const EnumDescriptor* foo_enum_;
+  const EnumValueDescriptor* foo_enum_value_;
+  const ServiceDescriptor* foo_service_;
+  const FieldDescriptor* foo_extension_;
+
+  const Descriptor* bar_message_;
+  const EnumDescriptor* bar_enum_;
+  const EnumValueDescriptor* bar_enum_value_;
+  const ServiceDescriptor* bar_service_;
+  const FieldDescriptor* bar_extension_;
+};
+
+TEST_F(FileDescriptorTest, Name) {
+  EXPECT_EQ("foo.proto", foo_file_->name());
+  EXPECT_EQ("bar.proto", bar_file_->name());
+  EXPECT_EQ("baz.proto", baz_file_->name());
+}
+
+TEST_F(FileDescriptorTest, Package) {
+  EXPECT_EQ("", foo_file_->package());
+  EXPECT_EQ("bar_package", bar_file_->package());
+}
+
+TEST_F(FileDescriptorTest, Dependencies) {
+  EXPECT_EQ(0, foo_file_->dependency_count());
+  EXPECT_EQ(1, bar_file_->dependency_count());
+  EXPECT_EQ(foo_file_, bar_file_->dependency(0));
+}
+
+TEST_F(FileDescriptorTest, FindMessageTypeByName) {
+  EXPECT_EQ(foo_message_, foo_file_->FindMessageTypeByName("FooMessage"));
+  EXPECT_EQ(bar_message_, bar_file_->FindMessageTypeByName("BarMessage"));
+
+  EXPECT_TRUE(foo_file_->FindMessageTypeByName("BarMessage") == nullptr);
+  EXPECT_TRUE(bar_file_->FindMessageTypeByName("FooMessage") == nullptr);
+  EXPECT_TRUE(baz_file_->FindMessageTypeByName("FooMessage") == nullptr);
+
+  EXPECT_TRUE(foo_file_->FindMessageTypeByName("NoSuchMessage") == nullptr);
+  EXPECT_TRUE(foo_file_->FindMessageTypeByName("FooEnum") == nullptr);
+}
+
+TEST_F(FileDescriptorTest, FindEnumTypeByName) {
+  EXPECT_EQ(foo_enum_, foo_file_->FindEnumTypeByName("FooEnum"));
+  EXPECT_EQ(bar_enum_, bar_file_->FindEnumTypeByName("BarEnum"));
+
+  EXPECT_TRUE(foo_file_->FindEnumTypeByName("BarEnum") == nullptr);
+  EXPECT_TRUE(bar_file_->FindEnumTypeByName("FooEnum") == nullptr);
+  EXPECT_TRUE(baz_file_->FindEnumTypeByName("FooEnum") == nullptr);
+
+  EXPECT_TRUE(foo_file_->FindEnumTypeByName("NoSuchEnum") == nullptr);
+  EXPECT_TRUE(foo_file_->FindEnumTypeByName("FooMessage") == nullptr);
+}
+
+TEST_F(FileDescriptorTest, FindEnumValueByName) {
+  EXPECT_EQ(foo_enum_value_, foo_file_->FindEnumValueByName("FOO_ENUM_VALUE"));
+  EXPECT_EQ(bar_enum_value_, bar_file_->FindEnumValueByName("BAR_ENUM_VALUE"));
+
+  EXPECT_TRUE(foo_file_->FindEnumValueByName("BAR_ENUM_VALUE") == nullptr);
+  EXPECT_TRUE(bar_file_->FindEnumValueByName("FOO_ENUM_VALUE") == nullptr);
+  EXPECT_TRUE(baz_file_->FindEnumValueByName("FOO_ENUM_VALUE") == nullptr);
+
+  EXPECT_TRUE(foo_file_->FindEnumValueByName("NO_SUCH_VALUE") == nullptr);
+  EXPECT_TRUE(foo_file_->FindEnumValueByName("FooMessage") == nullptr);
+}
+
+TEST_F(FileDescriptorTest, FindServiceByName) {
+  EXPECT_EQ(foo_service_, foo_file_->FindServiceByName("FooService"));
+  EXPECT_EQ(bar_service_, bar_file_->FindServiceByName("BarService"));
+
+  EXPECT_TRUE(foo_file_->FindServiceByName("BarService") == nullptr);
+  EXPECT_TRUE(bar_file_->FindServiceByName("FooService") == nullptr);
+  EXPECT_TRUE(baz_file_->FindServiceByName("FooService") == nullptr);
+
+  EXPECT_TRUE(foo_file_->FindServiceByName("NoSuchService") == nullptr);
+  EXPECT_TRUE(foo_file_->FindServiceByName("FooMessage") == nullptr);
+}
+
+TEST_F(FileDescriptorTest, FindExtensionByName) {
+  EXPECT_EQ(foo_extension_, foo_file_->FindExtensionByName("foo_extension"));
+  EXPECT_EQ(bar_extension_, bar_file_->FindExtensionByName("bar_extension"));
+
+  EXPECT_TRUE(foo_file_->FindExtensionByName("bar_extension") == nullptr);
+  EXPECT_TRUE(bar_file_->FindExtensionByName("foo_extension") == nullptr);
+  EXPECT_TRUE(baz_file_->FindExtensionByName("foo_extension") == nullptr);
+
+  EXPECT_TRUE(foo_file_->FindExtensionByName("no_such_extension") == nullptr);
+  EXPECT_TRUE(foo_file_->FindExtensionByName("FooMessage") == nullptr);
+}
+
+TEST_F(FileDescriptorTest, FindExtensionByNumber) {
+  EXPECT_EQ(foo_extension_, pool_.FindExtensionByNumber(foo_message_, 1));
+  EXPECT_EQ(bar_extension_, pool_.FindExtensionByNumber(bar_message_, 1));
+
+  EXPECT_TRUE(pool_.FindExtensionByNumber(foo_message_, 2) == nullptr);
+}
+
+
+TEST_F(FileDescriptorTest, BuildAgain) {
+  // Test that if we call BuildFile again on the same input we get the same
+  // FileDescriptor back.
+  FileDescriptorProto file;
+  foo_file_->CopyTo(&file);
+  EXPECT_EQ(foo_file_, pool_.BuildFile(file));
+
+  // But if we change the file then it won't work.
+  file.set_package("some.other.package");
+  EXPECT_TRUE(pool_.BuildFile(file) == nullptr);
+}
+
+TEST_F(FileDescriptorTest, BuildAgainWithSyntax) {
+  // Test that if we call BuildFile again on the same input we get the same
+  // FileDescriptor back even if syntax param is specified.
+  FileDescriptorProto proto_syntax2;
+  proto_syntax2.set_name("foo_syntax2");
+  proto_syntax2.set_syntax("proto2");
+
+  const FileDescriptor* proto2_descriptor = pool_.BuildFile(proto_syntax2);
+  EXPECT_TRUE(proto2_descriptor != nullptr);
+  EXPECT_EQ(proto2_descriptor, pool_.BuildFile(proto_syntax2));
+
+  FileDescriptorProto implicit_proto2;
+  implicit_proto2.set_name("foo_implicit_syntax2");
+
+  const FileDescriptor* implicit_proto2_descriptor =
+      pool_.BuildFile(implicit_proto2);
+  EXPECT_TRUE(implicit_proto2_descriptor != nullptr);
+  // We get the same FileDescriptor back if syntax param is explicitly
+  // specified.
+  implicit_proto2.set_syntax("proto2");
+  EXPECT_EQ(implicit_proto2_descriptor, pool_.BuildFile(implicit_proto2));
+
+  FileDescriptorProto proto_syntax3;
+  proto_syntax3.set_name("foo_syntax3");
+  proto_syntax3.set_syntax("proto3");
+
+  const FileDescriptor* proto3_descriptor = pool_.BuildFile(proto_syntax3);
+  EXPECT_TRUE(proto3_descriptor != nullptr);
+  EXPECT_EQ(proto3_descriptor, pool_.BuildFile(proto_syntax3));
+}
+
+TEST_F(FileDescriptorTest, Syntax) {
+  FileDescriptorProto proto;
+  proto.set_name("foo");
+  // Enable the test when we also populate the syntax for proto2.
+#if 0
+  {
+    proto.set_syntax("proto2");
+    DescriptorPool pool;
+    const FileDescriptor* file = pool.BuildFile(proto);
+    EXPECT_TRUE(file != nullptr);
+    EXPECT_EQ(FileDescriptor::SYNTAX_PROTO2, file->syntax());
+    FileDescriptorProto other;
+    file->CopyTo(&other);
+    EXPECT_EQ("proto2", other.syntax());
+  }
+#endif
+  {
+    proto.set_syntax("proto3");
+    DescriptorPool pool;
+    const FileDescriptor* file = pool.BuildFile(proto);
+    EXPECT_TRUE(file != nullptr);
+    EXPECT_EQ(FileDescriptor::SYNTAX_PROTO3, file->syntax());
+    FileDescriptorProto other;
+    file->CopyTo(&other);
+    EXPECT_EQ("proto3", other.syntax());
+  }
+}
+
+void ExtractDebugString(
+    const FileDescriptor* file, std::set<std::string>* visited,
+    std::vector<std::pair<std::string, std::string>>* debug_strings) {
+  if (!visited->insert(file->name()).second) {
+    return;
+  }
+  for (int i = 0; i < file->dependency_count(); ++i) {
+    ExtractDebugString(file->dependency(i), visited, debug_strings);
+  }
+  debug_strings->push_back(std::make_pair(file->name(), file->DebugString()));
+}
+
+class SimpleErrorCollector : public io::ErrorCollector {
+ public:
+  // implements ErrorCollector ---------------------------------------
+  void AddError(int line, int column, const std::string& message) override {
+    last_error_ = StringPrintf("%d:%d:", line, column) + message;
+  }
+
+  const std::string& last_error() { return last_error_; }
+
+ private:
+  std::string last_error_;
+};
+// Test that the result of FileDescriptor::DebugString() can be used to create
+// the original descriptors.
+TEST_F(FileDescriptorTest, DebugStringRoundTrip) {
+  std::set<std::string> visited;
+  std::vector<std::pair<std::string, std::string>> debug_strings;
+  ExtractDebugString(protobuf_unittest::TestAllTypes::descriptor()->file(),
+                     &visited, &debug_strings);
+  ExtractDebugString(
+      protobuf_unittest::TestMessageWithCustomOptions::descriptor()->file(),
+      &visited, &debug_strings);
+  ExtractDebugString(proto3_arena_unittest::TestAllTypes::descriptor()->file(),
+                     &visited, &debug_strings);
+  ASSERT_GE(debug_strings.size(), 3);
+
+  DescriptorPool pool;
+  for (int i = 0; i < debug_strings.size(); ++i) {
+    const std::string& name = debug_strings[i].first;
+    const std::string& content = debug_strings[i].second;
+    io::ArrayInputStream input_stream(content.data(), content.size());
+    SimpleErrorCollector error_collector;
+    io::Tokenizer tokenizer(&input_stream, &error_collector);
+    compiler::Parser parser;
+    parser.RecordErrorsTo(&error_collector);
+    FileDescriptorProto proto;
+    ASSERT_TRUE(parser.Parse(&tokenizer, &proto))
+        << error_collector.last_error() << "\n"
+        << content;
+    ASSERT_EQ("", error_collector.last_error());
+    proto.set_name(name);
+    const FileDescriptor* descriptor = pool.BuildFile(proto);
+    ASSERT_TRUE(descriptor != nullptr) << proto.DebugString();
+    EXPECT_EQ(content, descriptor->DebugString());
+  }
+}
+
+// ===================================================================
+
+// Test simple flat messages and fields.
+class DescriptorTest : public testing::Test {
+ protected:
+  void SetUp() override {
+    // Build descriptors for the following definitions:
+    //
+    //   // in "foo.proto"
+    //   message TestForeign {}
+    //   enum TestEnum {}
+    //
+    //   message TestMessage {
+    //     required string      foo = 1;
+    //     optional TestEnum    bar = 6;
+    //     repeated TestForeign baz = 500000000;
+    //     optional group       qux = 15 {}
+    //   }
+    //
+    //   // in "bar.proto"
+    //   package corge.grault;
+    //   message TestMessage2 {
+    //     required string foo = 1;
+    //     required string bar = 2;
+    //     required string quux = 6;
+    //   }
+    //
+    //   // in "map.proto"
+    //   message TestMessage3 {
+    //     map<int32, int32> map_int32_int32 = 1;
+    //   }
+    //
+    //   // in "json.proto"
+    //   message TestMessage4 {
+    //     optional int32 field_name1 = 1;
+    //     optional int32 fieldName2 = 2;
+    //     optional int32 FieldName3 = 3;
+    //     optional int32 _field_name4 = 4;
+    //     optional int32 FIELD_NAME5 = 5;
+    //     optional int32 field_name6 = 6 [json_name = "@type"];
+    //   }
+    //
+    // We cheat and use TestForeign as the type for qux rather than create
+    // an actual nested type.
+    //
+    // Since all primitive types (including string) use the same building
+    // code, there's no need to test each one individually.
+    //
+    // TestMessage2 is primarily here to test FindFieldByName and friends.
+    // All messages created from the same DescriptorPool share the same lookup
+    // table, so we need to insure that they don't interfere.
+
+    FileDescriptorProto foo_file;
+    foo_file.set_name("foo.proto");
+    AddMessage(&foo_file, "TestForeign");
+    AddEmptyEnum(&foo_file, "TestEnum");
+
+    DescriptorProto* message = AddMessage(&foo_file, "TestMessage");
+    AddField(message, "foo", 1, FieldDescriptorProto::LABEL_REQUIRED,
+             FieldDescriptorProto::TYPE_STRING);
+    AddField(message, "bar", 6, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_ENUM)
+        ->set_type_name("TestEnum");
+    AddField(message, "baz", 500000000, FieldDescriptorProto::LABEL_REPEATED,
+             FieldDescriptorProto::TYPE_MESSAGE)
+        ->set_type_name("TestForeign");
+    AddField(message, "qux", 15, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_GROUP)
+        ->set_type_name("TestForeign");
+
+    FileDescriptorProto bar_file;
+    bar_file.set_name("bar.proto");
+    bar_file.set_package("corge.grault");
+
+    DescriptorProto* message2 = AddMessage(&bar_file, "TestMessage2");
+    AddField(message2, "foo", 1, FieldDescriptorProto::LABEL_REQUIRED,
+             FieldDescriptorProto::TYPE_STRING);
+    AddField(message2, "bar", 2, FieldDescriptorProto::LABEL_REQUIRED,
+             FieldDescriptorProto::TYPE_STRING);
+    AddField(message2, "quux", 6, FieldDescriptorProto::LABEL_REQUIRED,
+             FieldDescriptorProto::TYPE_STRING);
+
+    FileDescriptorProto map_file;
+    map_file.set_name("map.proto");
+    DescriptorProto* message3 = AddMessage(&map_file, "TestMessage3");
+
+    DescriptorProto* entry = AddNestedMessage(message3, "MapInt32Int32Entry");
+    AddField(entry, "key", 1, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_INT32);
+    AddField(entry, "value", 2, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_INT32);
+    entry->mutable_options()->set_map_entry(true);
+
+    AddField(message3, "map_int32_int32", 1,
+             FieldDescriptorProto::LABEL_REPEATED,
+             FieldDescriptorProto::TYPE_MESSAGE)
+        ->set_type_name("MapInt32Int32Entry");
+
+    FileDescriptorProto json_file;
+    json_file.set_name("json.proto");
+    json_file.set_syntax("proto3");
+    DescriptorProto* message4 = AddMessage(&json_file, "TestMessage4");
+    AddField(message4, "field_name1", 1, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_INT32);
+    AddField(message4, "fieldName2", 2, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_INT32);
+    AddField(message4, "FieldName3", 3, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_INT32);
+    AddField(message4, "_field_name4", 4, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_INT32);
+    AddField(message4, "FIELD_NAME5", 5, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_INT32);
+    AddField(message4, "field_name6", 6, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_INT32)
+        ->set_json_name("@type");
+    AddField(message4, "fieldname7", 7, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_INT32);
+
+    // Build the descriptors and get the pointers.
+    foo_file_ = pool_.BuildFile(foo_file);
+    ASSERT_TRUE(foo_file_ != nullptr);
+
+    bar_file_ = pool_.BuildFile(bar_file);
+    ASSERT_TRUE(bar_file_ != nullptr);
+
+    map_file_ = pool_.BuildFile(map_file);
+    ASSERT_TRUE(map_file_ != nullptr);
+
+    json_file_ = pool_.BuildFile(json_file);
+    ASSERT_TRUE(json_file_ != nullptr);
+
+    ASSERT_EQ(1, foo_file_->enum_type_count());
+    enum_ = foo_file_->enum_type(0);
+
+    ASSERT_EQ(2, foo_file_->message_type_count());
+    foreign_ = foo_file_->message_type(0);
+    message_ = foo_file_->message_type(1);
+
+    ASSERT_EQ(4, message_->field_count());
+    foo_ = message_->field(0);
+    bar_ = message_->field(1);
+    baz_ = message_->field(2);
+    qux_ = message_->field(3);
+
+    ASSERT_EQ(1, bar_file_->message_type_count());
+    message2_ = bar_file_->message_type(0);
+
+    ASSERT_EQ(3, message2_->field_count());
+    foo2_ = message2_->field(0);
+    bar2_ = message2_->field(1);
+    quux2_ = message2_->field(2);
+
+    ASSERT_EQ(1, map_file_->message_type_count());
+    message3_ = map_file_->message_type(0);
+
+    ASSERT_EQ(1, message3_->field_count());
+    map_ = message3_->field(0);
+
+    ASSERT_EQ(1, json_file_->message_type_count());
+    message4_ = json_file_->message_type(0);
+  }
+
+  void CopyWithJsonName(const Descriptor* message, DescriptorProto* proto) {
+    message->CopyTo(proto);
+    message->CopyJsonNameTo(proto);
+  }
+
+  const EnumValueDescriptor* FindValueByNumberCreatingIfUnknown(
+      const EnumDescriptor* desc, int number) {
+    return desc->FindValueByNumberCreatingIfUnknown(number);
+  }
+
+  DescriptorPool pool_;
+
+  const FileDescriptor* foo_file_;
+  const FileDescriptor* bar_file_;
+  const FileDescriptor* map_file_;
+  const FileDescriptor* json_file_;
+
+  const Descriptor* message_;
+  const Descriptor* message2_;
+  const Descriptor* message3_;
+  const Descriptor* message4_;
+  const Descriptor* foreign_;
+  const EnumDescriptor* enum_;
+
+  const FieldDescriptor* foo_;
+  const FieldDescriptor* bar_;
+  const FieldDescriptor* baz_;
+  const FieldDescriptor* qux_;
+
+  const FieldDescriptor* foo2_;
+  const FieldDescriptor* bar2_;
+  const FieldDescriptor* quux2_;
+
+  const FieldDescriptor* map_;
+};
+
+TEST_F(DescriptorTest, Name) {
+  EXPECT_EQ("TestMessage", message_->name());
+  EXPECT_EQ("TestMessage", message_->full_name());
+  EXPECT_EQ(foo_file_, message_->file());
+
+  EXPECT_EQ("TestMessage2", message2_->name());
+  EXPECT_EQ("corge.grault.TestMessage2", message2_->full_name());
+  EXPECT_EQ(bar_file_, message2_->file());
+}
+
+TEST_F(DescriptorTest, ContainingType) {
+  EXPECT_TRUE(message_->containing_type() == nullptr);
+  EXPECT_TRUE(message2_->containing_type() == nullptr);
+}
+
+TEST_F(DescriptorTest, FieldNamesDedup) {
+  const auto collect_unique_names = [](const FieldDescriptor* field) {
+    std::set<std::string> names{field->name(), field->lowercase_name(),
+                                field->camelcase_name(), field->json_name()};
+    // Verify that we have the same number of string objects as we have string
+    // values. That is, duplicate names use the same std::string object.
+    // This is for memory efficiency.
+    EXPECT_EQ(names.size(), (std::set<const std::string*>{
+                                &field->name(), &field->lowercase_name(),
+                                &field->camelcase_name(), &field->json_name()}
+                                 .size()))
+        << testing::PrintToString(names);
+    return names;
+  };
+
+  using testing::ElementsAre;
+  // field_name1
+  EXPECT_THAT(collect_unique_names(message4_->field(0)),
+              ElementsAre("fieldName1", "field_name1"));
+  // fieldName2
+  EXPECT_THAT(collect_unique_names(message4_->field(1)),
+              ElementsAre("fieldName2", "fieldname2"));
+  // FieldName3
+  EXPECT_THAT(collect_unique_names(message4_->field(2)),
+              ElementsAre("FieldName3", "fieldName3", "fieldname3"));
+  // _field_name4
+  EXPECT_THAT(collect_unique_names(message4_->field(3)),
+              ElementsAre("FieldName4", "_field_name4", "fieldName4"));
+  // FIELD_NAME5
+  EXPECT_THAT(
+      collect_unique_names(message4_->field(4)),
+      ElementsAre("FIELDNAME5", "FIELD_NAME5", "fIELDNAME5", "field_name5"));
+  // field_name6, with json name @type
+  EXPECT_THAT(collect_unique_names(message4_->field(5)),
+              ElementsAre("@type", "fieldName6", "field_name6"));
+  // fieldname7
+  EXPECT_THAT(collect_unique_names(message4_->field(6)),
+              ElementsAre("fieldname7"));
+}
+
+TEST_F(DescriptorTest, FieldsByIndex) {
+  ASSERT_EQ(4, message_->field_count());
+  EXPECT_EQ(foo_, message_->field(0));
+  EXPECT_EQ(bar_, message_->field(1));
+  EXPECT_EQ(baz_, message_->field(2));
+  EXPECT_EQ(qux_, message_->field(3));
+}
+
+TEST_F(DescriptorTest, FindFieldByName) {
+  // All messages in the same DescriptorPool share a single lookup table for
+  // fields.  So, in addition to testing that FindFieldByName finds the fields
+  // of the message, we need to test that it does *not* find the fields of
+  // *other* messages.
+
+  EXPECT_EQ(foo_, message_->FindFieldByName("foo"));
+  EXPECT_EQ(bar_, message_->FindFieldByName("bar"));
+  EXPECT_EQ(baz_, message_->FindFieldByName("baz"));
+  EXPECT_EQ(qux_, message_->FindFieldByName("qux"));
+  EXPECT_TRUE(message_->FindFieldByName("no_such_field") == nullptr);
+  EXPECT_TRUE(message_->FindFieldByName("quux") == nullptr);
+
+  EXPECT_EQ(foo2_, message2_->FindFieldByName("foo"));
+  EXPECT_EQ(bar2_, message2_->FindFieldByName("bar"));
+  EXPECT_EQ(quux2_, message2_->FindFieldByName("quux"));
+  EXPECT_TRUE(message2_->FindFieldByName("baz") == nullptr);
+  EXPECT_TRUE(message2_->FindFieldByName("qux") == nullptr);
+}
+
+TEST_F(DescriptorTest, FindFieldByNumber) {
+  EXPECT_EQ(foo_, message_->FindFieldByNumber(1));
+  EXPECT_EQ(bar_, message_->FindFieldByNumber(6));
+  EXPECT_EQ(baz_, message_->FindFieldByNumber(500000000));
+  EXPECT_EQ(qux_, message_->FindFieldByNumber(15));
+  EXPECT_TRUE(message_->FindFieldByNumber(837592) == nullptr);
+  EXPECT_TRUE(message_->FindFieldByNumber(2) == nullptr);
+
+  EXPECT_EQ(foo2_, message2_->FindFieldByNumber(1));
+  EXPECT_EQ(bar2_, message2_->FindFieldByNumber(2));
+  EXPECT_EQ(quux2_, message2_->FindFieldByNumber(6));
+  EXPECT_TRUE(message2_->FindFieldByNumber(15) == nullptr);
+  EXPECT_TRUE(message2_->FindFieldByNumber(500000000) == nullptr);
+}
+
+TEST_F(DescriptorTest, FieldName) {
+  EXPECT_EQ("foo", foo_->name());
+  EXPECT_EQ("bar", bar_->name());
+  EXPECT_EQ("baz", baz_->name());
+  EXPECT_EQ("qux", qux_->name());
+}
+
+TEST_F(DescriptorTest, FieldFullName) {
+  EXPECT_EQ("TestMessage.foo", foo_->full_name());
+  EXPECT_EQ("TestMessage.bar", bar_->full_name());
+  EXPECT_EQ("TestMessage.baz", baz_->full_name());
+  EXPECT_EQ("TestMessage.qux", qux_->full_name());
+
+  EXPECT_EQ("corge.grault.TestMessage2.foo", foo2_->full_name());
+  EXPECT_EQ("corge.grault.TestMessage2.bar", bar2_->full_name());
+  EXPECT_EQ("corge.grault.TestMessage2.quux", quux2_->full_name());
+}
+
+TEST_F(DescriptorTest, PrintableNameIsFullNameForNonExtensionFields) {
+  EXPECT_EQ("TestMessage.foo", foo_->PrintableNameForExtension());
+  EXPECT_EQ("TestMessage.bar", bar_->PrintableNameForExtension());
+  EXPECT_EQ("TestMessage.baz", baz_->PrintableNameForExtension());
+  EXPECT_EQ("TestMessage.qux", qux_->PrintableNameForExtension());
+
+  EXPECT_EQ("corge.grault.TestMessage2.foo",
+            foo2_->PrintableNameForExtension());
+  EXPECT_EQ("corge.grault.TestMessage2.bar",
+            bar2_->PrintableNameForExtension());
+  EXPECT_EQ("corge.grault.TestMessage2.quux",
+            quux2_->PrintableNameForExtension());
+}
+
+TEST_F(DescriptorTest, PrintableNameIsFullNameForNonMessageSetExtension) {
+  EXPECT_EQ("protobuf_unittest.Aggregate.nested",
+            protobuf_unittest::Aggregate::descriptor()
+                ->FindExtensionByName("nested")
+                ->PrintableNameForExtension());
+}
+
+TEST_F(DescriptorTest, PrintableNameIsExtendingTypeForMessageSetExtension) {
+  EXPECT_EQ("protobuf_unittest.AggregateMessageSetElement",
+            protobuf_unittest::AggregateMessageSetElement::descriptor()
+                ->FindExtensionByName("message_set_extension")
+                ->PrintableNameForExtension());
+}
+
+TEST_F(DescriptorTest, FieldJsonName) {
+  EXPECT_EQ("fieldName1", message4_->field(0)->json_name());
+  EXPECT_EQ("fieldName2", message4_->field(1)->json_name());
+  EXPECT_EQ("FieldName3", message4_->field(2)->json_name());
+  EXPECT_EQ("FieldName4", message4_->field(3)->json_name());
+  EXPECT_EQ("FIELDNAME5", message4_->field(4)->json_name());
+  EXPECT_EQ("@type", message4_->field(5)->json_name());
+
+  DescriptorProto proto;
+  message4_->CopyTo(&proto);
+  ASSERT_EQ(7, proto.field_size());
+  EXPECT_FALSE(proto.field(0).has_json_name());
+  EXPECT_FALSE(proto.field(1).has_json_name());
+  EXPECT_FALSE(proto.field(2).has_json_name());
+  EXPECT_FALSE(proto.field(3).has_json_name());
+  EXPECT_FALSE(proto.field(4).has_json_name());
+  EXPECT_EQ("@type", proto.field(5).json_name());
+  EXPECT_FALSE(proto.field(6).has_json_name());
+
+  proto.Clear();
+  CopyWithJsonName(message4_, &proto);
+  ASSERT_EQ(7, proto.field_size());
+  EXPECT_EQ("fieldName1", proto.field(0).json_name());
+  EXPECT_EQ("fieldName2", proto.field(1).json_name());
+  EXPECT_EQ("FieldName3", proto.field(2).json_name());
+  EXPECT_EQ("FieldName4", proto.field(3).json_name());
+  EXPECT_EQ("FIELDNAME5", proto.field(4).json_name());
+  EXPECT_EQ("@type", proto.field(5).json_name());
+  EXPECT_EQ("fieldname7", proto.field(6).json_name());
+
+  // Test generated descriptor.
+  const Descriptor* generated = protobuf_unittest::TestJsonName::descriptor();
+  ASSERT_EQ(7, generated->field_count());
+  EXPECT_EQ("fieldName1", generated->field(0)->json_name());
+  EXPECT_EQ("fieldName2", generated->field(1)->json_name());
+  EXPECT_EQ("FieldName3", generated->field(2)->json_name());
+  EXPECT_EQ("FieldName4", generated->field(3)->json_name());
+  EXPECT_EQ("FIELDNAME5", generated->field(4)->json_name());
+  EXPECT_EQ("@type", generated->field(5)->json_name());
+  EXPECT_EQ("fieldname7", generated->field(6)->json_name());
+}
+
+TEST_F(DescriptorTest, FieldFile) {
+  EXPECT_EQ(foo_file_, foo_->file());
+  EXPECT_EQ(foo_file_, bar_->file());
+  EXPECT_EQ(foo_file_, baz_->file());
+  EXPECT_EQ(foo_file_, qux_->file());
+
+  EXPECT_EQ(bar_file_, foo2_->file());
+  EXPECT_EQ(bar_file_, bar2_->file());
+  EXPECT_EQ(bar_file_, quux2_->file());
+}
+
+TEST_F(DescriptorTest, FieldIndex) {
+  EXPECT_EQ(0, foo_->index());
+  EXPECT_EQ(1, bar_->index());
+  EXPECT_EQ(2, baz_->index());
+  EXPECT_EQ(3, qux_->index());
+}
+
+TEST_F(DescriptorTest, FieldNumber) {
+  EXPECT_EQ(1, foo_->number());
+  EXPECT_EQ(6, bar_->number());
+  EXPECT_EQ(500000000, baz_->number());
+  EXPECT_EQ(15, qux_->number());
+}
+
+TEST_F(DescriptorTest, FieldType) {
+  EXPECT_EQ(FieldDescriptor::TYPE_STRING, foo_->type());
+  EXPECT_EQ(FieldDescriptor::TYPE_ENUM, bar_->type());
+  EXPECT_EQ(FieldDescriptor::TYPE_MESSAGE, baz_->type());
+  EXPECT_EQ(FieldDescriptor::TYPE_GROUP, qux_->type());
+}
+
+TEST_F(DescriptorTest, FieldLabel) {
+  EXPECT_EQ(FieldDescriptor::LABEL_REQUIRED, foo_->label());
+  EXPECT_EQ(FieldDescriptor::LABEL_OPTIONAL, bar_->label());
+  EXPECT_EQ(FieldDescriptor::LABEL_REPEATED, baz_->label());
+  EXPECT_EQ(FieldDescriptor::LABEL_OPTIONAL, qux_->label());
+
+  EXPECT_TRUE(foo_->is_required());
+  EXPECT_FALSE(foo_->is_optional());
+  EXPECT_FALSE(foo_->is_repeated());
+
+  EXPECT_FALSE(bar_->is_required());
+  EXPECT_TRUE(bar_->is_optional());
+  EXPECT_FALSE(bar_->is_repeated());
+
+  EXPECT_FALSE(baz_->is_required());
+  EXPECT_FALSE(baz_->is_optional());
+  EXPECT_TRUE(baz_->is_repeated());
+}
+
+TEST_F(DescriptorTest, IsMap) {
+  EXPECT_TRUE(map_->is_map());
+  EXPECT_FALSE(baz_->is_map());
+  EXPECT_TRUE(map_->message_type()->options().map_entry());
+}
+
+TEST_F(DescriptorTest, GetMap) {
+  const Descriptor* map_desc = map_->message_type();
+  const FieldDescriptor* map_key = map_desc->map_key();
+  ASSERT_TRUE(map_key != nullptr);
+  EXPECT_EQ(map_key->name(), "key");
+  EXPECT_EQ(map_key->number(), 1);
+
+  const FieldDescriptor* map_value = map_desc->map_value();
+  ASSERT_TRUE(map_value != nullptr);
+  EXPECT_EQ(map_value->name(), "value");
+  EXPECT_EQ(map_value->number(), 2);
+
+  EXPECT_EQ(message_->map_key(), nullptr);
+  EXPECT_EQ(message_->map_value(), nullptr);
+}
+
+TEST_F(DescriptorTest, FieldHasDefault) {
+  EXPECT_FALSE(foo_->has_default_value());
+  EXPECT_FALSE(bar_->has_default_value());
+  EXPECT_FALSE(baz_->has_default_value());
+  EXPECT_FALSE(qux_->has_default_value());
+}
+
+TEST_F(DescriptorTest, FieldContainingType) {
+  EXPECT_EQ(message_, foo_->containing_type());
+  EXPECT_EQ(message_, bar_->containing_type());
+  EXPECT_EQ(message_, baz_->containing_type());
+  EXPECT_EQ(message_, qux_->containing_type());
+
+  EXPECT_EQ(message2_, foo2_->containing_type());
+  EXPECT_EQ(message2_, bar2_->containing_type());
+  EXPECT_EQ(message2_, quux2_->containing_type());
+}
+
+TEST_F(DescriptorTest, FieldMessageType) {
+  EXPECT_TRUE(foo_->message_type() == nullptr);
+  EXPECT_TRUE(bar_->message_type() == nullptr);
+
+  EXPECT_EQ(foreign_, baz_->message_type());
+  EXPECT_EQ(foreign_, qux_->message_type());
+}
+
+TEST_F(DescriptorTest, FieldEnumType) {
+  EXPECT_TRUE(foo_->enum_type() == nullptr);
+  EXPECT_TRUE(baz_->enum_type() == nullptr);
+  EXPECT_TRUE(qux_->enum_type() == nullptr);
+
+  EXPECT_EQ(enum_, bar_->enum_type());
+}
+
+
+// ===================================================================
+
+// Test simple flat messages and fields.
+class OneofDescriptorTest : public testing::Test {
+ protected:
+  void SetUp() override {
+    // Build descriptors for the following definitions:
+    //
+    //   package garply;
+    //   message TestOneof {
+    //     optional int32 a = 1;
+    //     oneof foo {
+    //       string b = 2;
+    //       TestOneof c = 3;
+    //     }
+    //     oneof bar {
+    //       float d = 4;
+    //     }
+    //   }
+
+    FileDescriptorProto baz_file;
+    baz_file.set_name("baz.proto");
+    baz_file.set_package("garply");
+
+    DescriptorProto* oneof_message = AddMessage(&baz_file, "TestOneof");
+    oneof_message->add_oneof_decl()->set_name("foo");
+    oneof_message->add_oneof_decl()->set_name("bar");
+
+    AddField(oneof_message, "a", 1, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_INT32);
+    AddField(oneof_message, "b", 2, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_STRING);
+    oneof_message->mutable_field(1)->set_oneof_index(0);
+    AddField(oneof_message, "c", 3, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_MESSAGE);
+    oneof_message->mutable_field(2)->set_oneof_index(0);
+    oneof_message->mutable_field(2)->set_type_name("TestOneof");
+
+    AddField(oneof_message, "d", 4, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_FLOAT);
+    oneof_message->mutable_field(3)->set_oneof_index(1);
+
+    // Build the descriptors and get the pointers.
+    baz_file_ = pool_.BuildFile(baz_file);
+    ASSERT_TRUE(baz_file_ != nullptr);
+
+    ASSERT_EQ(1, baz_file_->message_type_count());
+    oneof_message_ = baz_file_->message_type(0);
+
+    ASSERT_EQ(2, oneof_message_->oneof_decl_count());
+    oneof_ = oneof_message_->oneof_decl(0);
+    oneof2_ = oneof_message_->oneof_decl(1);
+
+    ASSERT_EQ(4, oneof_message_->field_count());
+    a_ = oneof_message_->field(0);
+    b_ = oneof_message_->field(1);
+    c_ = oneof_message_->field(2);
+    d_ = oneof_message_->field(3);
+  }
+
+  DescriptorPool pool_;
+
+  const FileDescriptor* baz_file_;
+
+  const Descriptor* oneof_message_;
+
+  const OneofDescriptor* oneof_;
+  const OneofDescriptor* oneof2_;
+  const FieldDescriptor* a_;
+  const FieldDescriptor* b_;
+  const FieldDescriptor* c_;
+  const FieldDescriptor* d_;
+};
+
+TEST_F(OneofDescriptorTest, Normal) {
+  EXPECT_EQ("foo", oneof_->name());
+  EXPECT_EQ("garply.TestOneof.foo", oneof_->full_name());
+  EXPECT_EQ(0, oneof_->index());
+  ASSERT_EQ(2, oneof_->field_count());
+  EXPECT_EQ(b_, oneof_->field(0));
+  EXPECT_EQ(c_, oneof_->field(1));
+  EXPECT_TRUE(a_->containing_oneof() == nullptr);
+  EXPECT_EQ(oneof_, b_->containing_oneof());
+  EXPECT_EQ(oneof_, c_->containing_oneof());
+}
+
+TEST_F(OneofDescriptorTest, FindByName) {
+  EXPECT_EQ(oneof_, oneof_message_->FindOneofByName("foo"));
+  EXPECT_EQ(oneof2_, oneof_message_->FindOneofByName("bar"));
+  EXPECT_TRUE(oneof_message_->FindOneofByName("no_such_oneof") == nullptr);
+}
+
+// ===================================================================
+
+class StylizedFieldNamesTest : public testing::Test {
+ protected:
+  void SetUp() override {
+    FileDescriptorProto file;
+    file.set_name("foo.proto");
+
+    AddExtensionRange(AddMessage(&file, "ExtendableMessage"), 1, 1000);
+
+    DescriptorProto* message = AddMessage(&file, "TestMessage");
+    AddField(message, "foo_foo", 1, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_INT32);
+    AddField(message, "FooBar", 2, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_INT32);
+    AddField(message, "fooBaz", 3, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_INT32);
+    AddField(message, "fooFoo", 4,  // Camel-case conflict with foo_foo.
+             FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_INT32);
+    AddField(message, "foobar", 5,  // Lower-case conflict with FooBar.
+             FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_INT32);
+
+    AddNestedExtension(message, "ExtendableMessage", "bar_foo", 1,
+                       FieldDescriptorProto::LABEL_OPTIONAL,
+                       FieldDescriptorProto::TYPE_INT32);
+    AddNestedExtension(message, "ExtendableMessage", "BarBar", 2,
+                       FieldDescriptorProto::LABEL_OPTIONAL,
+                       FieldDescriptorProto::TYPE_INT32);
+    AddNestedExtension(message, "ExtendableMessage", "BarBaz", 3,
+                       FieldDescriptorProto::LABEL_OPTIONAL,
+                       FieldDescriptorProto::TYPE_INT32);
+    AddNestedExtension(message, "ExtendableMessage", "barFoo", 4,  // Conflict
+                       FieldDescriptorProto::LABEL_OPTIONAL,
+                       FieldDescriptorProto::TYPE_INT32);
+    AddNestedExtension(message, "ExtendableMessage", "barbar", 5,  // Conflict
+                       FieldDescriptorProto::LABEL_OPTIONAL,
+                       FieldDescriptorProto::TYPE_INT32);
+
+    AddExtension(&file, "ExtendableMessage", "baz_foo", 11,
+                 FieldDescriptorProto::LABEL_OPTIONAL,
+                 FieldDescriptorProto::TYPE_INT32);
+    AddExtension(&file, "ExtendableMessage", "BazBar", 12,
+                 FieldDescriptorProto::LABEL_OPTIONAL,
+                 FieldDescriptorProto::TYPE_INT32);
+    AddExtension(&file, "ExtendableMessage", "BazBaz", 13,
+                 FieldDescriptorProto::LABEL_OPTIONAL,
+                 FieldDescriptorProto::TYPE_INT32);
+    AddExtension(&file, "ExtendableMessage", "bazFoo", 14,  // Conflict
+                 FieldDescriptorProto::LABEL_OPTIONAL,
+                 FieldDescriptorProto::TYPE_INT32);
+    AddExtension(&file, "ExtendableMessage", "bazbar", 15,  // Conflict
+                 FieldDescriptorProto::LABEL_OPTIONAL,
+                 FieldDescriptorProto::TYPE_INT32);
+
+    file_ = pool_.BuildFile(file);
+    ASSERT_TRUE(file_ != nullptr);
+    ASSERT_EQ(2, file_->message_type_count());
+    message_ = file_->message_type(1);
+    ASSERT_EQ("TestMessage", message_->name());
+    ASSERT_EQ(5, message_->field_count());
+    ASSERT_EQ(5, message_->extension_count());
+    ASSERT_EQ(5, file_->extension_count());
+  }
+
+  DescriptorPool pool_;
+  const FileDescriptor* file_;
+  const Descriptor* message_;
+};
+
+TEST_F(StylizedFieldNamesTest, LowercaseName) {
+  EXPECT_EQ("foo_foo", message_->field(0)->lowercase_name());
+  EXPECT_EQ("foobar", message_->field(1)->lowercase_name());
+  EXPECT_EQ("foobaz", message_->field(2)->lowercase_name());
+  EXPECT_EQ("foofoo", message_->field(3)->lowercase_name());
+  EXPECT_EQ("foobar", message_->field(4)->lowercase_name());
+
+  EXPECT_EQ("bar_foo", message_->extension(0)->lowercase_name());
+  EXPECT_EQ("barbar", message_->extension(1)->lowercase_name());
+  EXPECT_EQ("barbaz", message_->extension(2)->lowercase_name());
+  EXPECT_EQ("barfoo", message_->extension(3)->lowercase_name());
+  EXPECT_EQ("barbar", message_->extension(4)->lowercase_name());
+
+  EXPECT_EQ("baz_foo", file_->extension(0)->lowercase_name());
+  EXPECT_EQ("bazbar", file_->extension(1)->lowercase_name());
+  EXPECT_EQ("bazbaz", file_->extension(2)->lowercase_name());
+  EXPECT_EQ("bazfoo", file_->extension(3)->lowercase_name());
+  EXPECT_EQ("bazbar", file_->extension(4)->lowercase_name());
+}
+
+TEST_F(StylizedFieldNamesTest, CamelcaseName) {
+  EXPECT_EQ("fooFoo", message_->field(0)->camelcase_name());
+  EXPECT_EQ("fooBar", message_->field(1)->camelcase_name());
+  EXPECT_EQ("fooBaz", message_->field(2)->camelcase_name());
+  EXPECT_EQ("fooFoo", message_->field(3)->camelcase_name());
+  EXPECT_EQ("foobar", message_->field(4)->camelcase_name());
+
+  EXPECT_EQ("barFoo", message_->extension(0)->camelcase_name());
+  EXPECT_EQ("barBar", message_->extension(1)->camelcase_name());
+  EXPECT_EQ("barBaz", message_->extension(2)->camelcase_name());
+  EXPECT_EQ("barFoo", message_->extension(3)->camelcase_name());
+  EXPECT_EQ("barbar", message_->extension(4)->camelcase_name());
+
+  EXPECT_EQ("bazFoo", file_->extension(0)->camelcase_name());
+  EXPECT_EQ("bazBar", file_->extension(1)->camelcase_name());
+  EXPECT_EQ("bazBaz", file_->extension(2)->camelcase_name());
+  EXPECT_EQ("bazFoo", file_->extension(3)->camelcase_name());
+  EXPECT_EQ("bazbar", file_->extension(4)->camelcase_name());
+}
+
+TEST_F(StylizedFieldNamesTest, FindByLowercaseName) {
+  EXPECT_EQ(message_->field(0), message_->FindFieldByLowercaseName("foo_foo"));
+  EXPECT_EQ(message_->field(1), message_->FindFieldByLowercaseName("foobar"));
+  EXPECT_EQ(message_->field(2), message_->FindFieldByLowercaseName("foobaz"));
+  EXPECT_TRUE(message_->FindFieldByLowercaseName("FooBar") == nullptr);
+  EXPECT_TRUE(message_->FindFieldByLowercaseName("fooBaz") == nullptr);
+  EXPECT_TRUE(message_->FindFieldByLowercaseName("bar_foo") == nullptr);
+  EXPECT_TRUE(message_->FindFieldByLowercaseName("nosuchfield") == nullptr);
+
+  EXPECT_EQ(message_->extension(0),
+            message_->FindExtensionByLowercaseName("bar_foo"));
+  EXPECT_EQ(message_->extension(1),
+            message_->FindExtensionByLowercaseName("barbar"));
+  EXPECT_EQ(message_->extension(2),
+            message_->FindExtensionByLowercaseName("barbaz"));
+  EXPECT_TRUE(message_->FindExtensionByLowercaseName("BarBar") == nullptr);
+  EXPECT_TRUE(message_->FindExtensionByLowercaseName("barBaz") == nullptr);
+  EXPECT_TRUE(message_->FindExtensionByLowercaseName("foo_foo") == nullptr);
+  EXPECT_TRUE(message_->FindExtensionByLowercaseName("nosuchfield") == nullptr);
+
+  EXPECT_EQ(file_->extension(0),
+            file_->FindExtensionByLowercaseName("baz_foo"));
+  EXPECT_EQ(file_->extension(1), file_->FindExtensionByLowercaseName("bazbar"));
+  EXPECT_EQ(file_->extension(2), file_->FindExtensionByLowercaseName("bazbaz"));
+  EXPECT_TRUE(file_->FindExtensionByLowercaseName("BazBar") == nullptr);
+  EXPECT_TRUE(file_->FindExtensionByLowercaseName("bazBaz") == nullptr);
+  EXPECT_TRUE(file_->FindExtensionByLowercaseName("nosuchfield") == nullptr);
+}
+
+TEST_F(StylizedFieldNamesTest, FindByCamelcaseName) {
+  EXPECT_EQ(message_->field(0), message_->FindFieldByCamelcaseName("fooFoo"));
+  EXPECT_EQ(message_->field(1), message_->FindFieldByCamelcaseName("fooBar"));
+  EXPECT_EQ(message_->field(2), message_->FindFieldByCamelcaseName("fooBaz"));
+  EXPECT_TRUE(message_->FindFieldByCamelcaseName("foo_foo") == nullptr);
+  EXPECT_TRUE(message_->FindFieldByCamelcaseName("FooBar") == nullptr);
+  EXPECT_TRUE(message_->FindFieldByCamelcaseName("barFoo") == nullptr);
+  EXPECT_TRUE(message_->FindFieldByCamelcaseName("nosuchfield") == nullptr);
+
+  EXPECT_EQ(message_->extension(0),
+            message_->FindExtensionByCamelcaseName("barFoo"));
+  EXPECT_EQ(message_->extension(1),
+            message_->FindExtensionByCamelcaseName("barBar"));
+  EXPECT_EQ(message_->extension(2),
+            message_->FindExtensionByCamelcaseName("barBaz"));
+  EXPECT_TRUE(message_->FindExtensionByCamelcaseName("bar_foo") == nullptr);
+  EXPECT_TRUE(message_->FindExtensionByCamelcaseName("BarBar") == nullptr);
+  EXPECT_TRUE(message_->FindExtensionByCamelcaseName("fooFoo") == nullptr);
+  EXPECT_TRUE(message_->FindExtensionByCamelcaseName("nosuchfield") == nullptr);
+
+  EXPECT_EQ(file_->extension(0), file_->FindExtensionByCamelcaseName("bazFoo"));
+  EXPECT_EQ(file_->extension(1), file_->FindExtensionByCamelcaseName("bazBar"));
+  EXPECT_EQ(file_->extension(2), file_->FindExtensionByCamelcaseName("bazBaz"));
+  EXPECT_TRUE(file_->FindExtensionByCamelcaseName("baz_foo") == nullptr);
+  EXPECT_TRUE(file_->FindExtensionByCamelcaseName("BazBar") == nullptr);
+  EXPECT_TRUE(file_->FindExtensionByCamelcaseName("nosuchfield") == nullptr);
+}
+
+// ===================================================================
+
+// Test enum descriptors.
+class EnumDescriptorTest : public testing::Test {
+ protected:
+  void SetUp() override {
+    // Build descriptors for the following definitions:
+    //
+    //   // in "foo.proto"
+    //   enum TestEnum {
+    //     FOO = 1;
+    //     BAR = 2;
+    //   }
+    //
+    //   // in "bar.proto"
+    //   package corge.grault;
+    //   enum TestEnum2 {
+    //     FOO = 1;
+    //     BAZ = 3;
+    //   }
+    //
+    // TestEnum2 is primarily here to test FindValueByName and friends.
+    // All enums created from the same DescriptorPool share the same lookup
+    // table, so we need to insure that they don't interfere.
+
+    // TestEnum
+    FileDescriptorProto foo_file;
+    foo_file.set_name("foo.proto");
+
+    EnumDescriptorProto* enum_proto = AddEnum(&foo_file, "TestEnum");
+    AddEnumValue(enum_proto, "FOO", 1);
+    AddEnumValue(enum_proto, "BAR", 2);
+
+    // TestEnum2
+    FileDescriptorProto bar_file;
+    bar_file.set_name("bar.proto");
+    bar_file.set_package("corge.grault");
+
+    EnumDescriptorProto* enum2_proto = AddEnum(&bar_file, "TestEnum2");
+    AddEnumValue(enum2_proto, "FOO", 1);
+    AddEnumValue(enum2_proto, "BAZ", 3);
+
+    // Build the descriptors and get the pointers.
+    foo_file_ = pool_.BuildFile(foo_file);
+    ASSERT_TRUE(foo_file_ != nullptr);
+
+    bar_file_ = pool_.BuildFile(bar_file);
+    ASSERT_TRUE(bar_file_ != nullptr);
+
+    ASSERT_EQ(1, foo_file_->enum_type_count());
+    enum_ = foo_file_->enum_type(0);
+
+    ASSERT_EQ(2, enum_->value_count());
+    foo_ = enum_->value(0);
+    bar_ = enum_->value(1);
+
+    ASSERT_EQ(1, bar_file_->enum_type_count());
+    enum2_ = bar_file_->enum_type(0);
+
+    ASSERT_EQ(2, enum2_->value_count());
+    foo2_ = enum2_->value(0);
+    baz2_ = enum2_->value(1);
+  }
+
+  DescriptorPool pool_;
+
+  const FileDescriptor* foo_file_;
+  const FileDescriptor* bar_file_;
+
+  const EnumDescriptor* enum_;
+  const EnumDescriptor* enum2_;
+
+  const EnumValueDescriptor* foo_;
+  const EnumValueDescriptor* bar_;
+
+  const EnumValueDescriptor* foo2_;
+  const EnumValueDescriptor* baz2_;
+};
+
+TEST_F(EnumDescriptorTest, Name) {
+  EXPECT_EQ("TestEnum", enum_->name());
+  EXPECT_EQ("TestEnum", enum_->full_name());
+  EXPECT_EQ(foo_file_, enum_->file());
+
+  EXPECT_EQ("TestEnum2", enum2_->name());
+  EXPECT_EQ("corge.grault.TestEnum2", enum2_->full_name());
+  EXPECT_EQ(bar_file_, enum2_->file());
+}
+
+TEST_F(EnumDescriptorTest, ContainingType) {
+  EXPECT_TRUE(enum_->containing_type() == nullptr);
+  EXPECT_TRUE(enum2_->containing_type() == nullptr);
+}
+
+TEST_F(EnumDescriptorTest, ValuesByIndex) {
+  ASSERT_EQ(2, enum_->value_count());
+  EXPECT_EQ(foo_, enum_->value(0));
+  EXPECT_EQ(bar_, enum_->value(1));
+}
+
+TEST_F(EnumDescriptorTest, FindValueByName) {
+  EXPECT_EQ(foo_, enum_->FindValueByName("FOO"));
+  EXPECT_EQ(bar_, enum_->FindValueByName("BAR"));
+  EXPECT_EQ(foo2_, enum2_->FindValueByName("FOO"));
+  EXPECT_EQ(baz2_, enum2_->FindValueByName("BAZ"));
+
+  EXPECT_TRUE(enum_->FindValueByName("NO_SUCH_VALUE") == nullptr);
+  EXPECT_TRUE(enum_->FindValueByName("BAZ") == nullptr);
+  EXPECT_TRUE(enum2_->FindValueByName("BAR") == nullptr);
+}
+
+TEST_F(EnumDescriptorTest, FindValueByNumber) {
+  EXPECT_EQ(foo_, enum_->FindValueByNumber(1));
+  EXPECT_EQ(bar_, enum_->FindValueByNumber(2));
+  EXPECT_EQ(foo2_, enum2_->FindValueByNumber(1));
+  EXPECT_EQ(baz2_, enum2_->FindValueByNumber(3));
+
+  EXPECT_TRUE(enum_->FindValueByNumber(416) == nullptr);
+  EXPECT_TRUE(enum_->FindValueByNumber(3) == nullptr);
+  EXPECT_TRUE(enum2_->FindValueByNumber(2) == nullptr);
+}
+
+TEST_F(EnumDescriptorTest, ValueName) {
+  EXPECT_EQ("FOO", foo_->name());
+  EXPECT_EQ("BAR", bar_->name());
+}
+
+TEST_F(EnumDescriptorTest, ValueFullName) {
+  EXPECT_EQ("FOO", foo_->full_name());
+  EXPECT_EQ("BAR", bar_->full_name());
+  EXPECT_EQ("corge.grault.FOO", foo2_->full_name());
+  EXPECT_EQ("corge.grault.BAZ", baz2_->full_name());
+}
+
+TEST_F(EnumDescriptorTest, ValueIndex) {
+  EXPECT_EQ(0, foo_->index());
+  EXPECT_EQ(1, bar_->index());
+}
+
+TEST_F(EnumDescriptorTest, ValueNumber) {
+  EXPECT_EQ(1, foo_->number());
+  EXPECT_EQ(2, bar_->number());
+}
+
+TEST_F(EnumDescriptorTest, ValueType) {
+  EXPECT_EQ(enum_, foo_->type());
+  EXPECT_EQ(enum_, bar_->type());
+  EXPECT_EQ(enum2_, foo2_->type());
+  EXPECT_EQ(enum2_, baz2_->type());
+}
+
+// ===================================================================
+
+// Test service descriptors.
+class ServiceDescriptorTest : public testing::Test {
+ protected:
+  void SetUp() override {
+    // Build descriptors for the following messages and service:
+    //    // in "foo.proto"
+    //    message FooRequest  {}
+    //    message FooResponse {}
+    //    message BarRequest  {}
+    //    message BarResponse {}
+    //    message BazRequest  {}
+    //    message BazResponse {}
+    //
+    //    service TestService {
+    //      rpc Foo(FooRequest) returns (FooResponse);
+    //      rpc Bar(BarRequest) returns (BarResponse);
+    //    }
+    //
+    //    // in "bar.proto"
+    //    package corge.grault
+    //    service TestService2 {
+    //      rpc Foo(FooRequest) returns (FooResponse);
+    //      rpc Baz(BazRequest) returns (BazResponse);
+    //    }
+
+    FileDescriptorProto foo_file;
+    foo_file.set_name("foo.proto");
+
+    AddMessage(&foo_file, "FooRequest");
+    AddMessage(&foo_file, "FooResponse");
+    AddMessage(&foo_file, "BarRequest");
+    AddMessage(&foo_file, "BarResponse");
+    AddMessage(&foo_file, "BazRequest");
+    AddMessage(&foo_file, "BazResponse");
+
+    ServiceDescriptorProto* service = AddService(&foo_file, "TestService");
+    AddMethod(service, "Foo", "FooRequest", "FooResponse");
+    AddMethod(service, "Bar", "BarRequest", "BarResponse");
+
+    FileDescriptorProto bar_file;
+    bar_file.set_name("bar.proto");
+    bar_file.set_package("corge.grault");
+    bar_file.add_dependency("foo.proto");
+
+    ServiceDescriptorProto* service2 = AddService(&bar_file, "TestService2");
+    AddMethod(service2, "Foo", "FooRequest", "FooResponse");
+    AddMethod(service2, "Baz", "BazRequest", "BazResponse");
+
+    // Build the descriptors and get the pointers.
+    foo_file_ = pool_.BuildFile(foo_file);
+    ASSERT_TRUE(foo_file_ != nullptr);
+
+    bar_file_ = pool_.BuildFile(bar_file);
+    ASSERT_TRUE(bar_file_ != nullptr);
+
+    ASSERT_EQ(6, foo_file_->message_type_count());
+    foo_request_ = foo_file_->message_type(0);
+    foo_response_ = foo_file_->message_type(1);
+    bar_request_ = foo_file_->message_type(2);
+    bar_response_ = foo_file_->message_type(3);
+    baz_request_ = foo_file_->message_type(4);
+    baz_response_ = foo_file_->message_type(5);
+
+    ASSERT_EQ(1, foo_file_->service_count());
+    service_ = foo_file_->service(0);
+
+    ASSERT_EQ(2, service_->method_count());
+    foo_ = service_->method(0);
+    bar_ = service_->method(1);
+
+    ASSERT_EQ(1, bar_file_->service_count());
+    service2_ = bar_file_->service(0);
+
+    ASSERT_EQ(2, service2_->method_count());
+    foo2_ = service2_->method(0);
+    baz2_ = service2_->method(1);
+  }
+
+  DescriptorPool pool_;
+
+  const FileDescriptor* foo_file_;
+  const FileDescriptor* bar_file_;
+
+  const Descriptor* foo_request_;
+  const Descriptor* foo_response_;
+  const Descriptor* bar_request_;
+  const Descriptor* bar_response_;
+  const Descriptor* baz_request_;
+  const Descriptor* baz_response_;
+
+  const ServiceDescriptor* service_;
+  const ServiceDescriptor* service2_;
+
+  const MethodDescriptor* foo_;
+  const MethodDescriptor* bar_;
+
+  const MethodDescriptor* foo2_;
+  const MethodDescriptor* baz2_;
+};
+
+TEST_F(ServiceDescriptorTest, Name) {
+  EXPECT_EQ("TestService", service_->name());
+  EXPECT_EQ("TestService", service_->full_name());
+  EXPECT_EQ(foo_file_, service_->file());
+
+  EXPECT_EQ("TestService2", service2_->name());
+  EXPECT_EQ("corge.grault.TestService2", service2_->full_name());
+  EXPECT_EQ(bar_file_, service2_->file());
+}
+
+TEST_F(ServiceDescriptorTest, MethodsByIndex) {
+  ASSERT_EQ(2, service_->method_count());
+  EXPECT_EQ(foo_, service_->method(0));
+  EXPECT_EQ(bar_, service_->method(1));
+}
+
+TEST_F(ServiceDescriptorTest, FindMethodByName) {
+  EXPECT_EQ(foo_, service_->FindMethodByName("Foo"));
+  EXPECT_EQ(bar_, service_->FindMethodByName("Bar"));
+  EXPECT_EQ(foo2_, service2_->FindMethodByName("Foo"));
+  EXPECT_EQ(baz2_, service2_->FindMethodByName("Baz"));
+
+  EXPECT_TRUE(service_->FindMethodByName("NoSuchMethod") == nullptr);
+  EXPECT_TRUE(service_->FindMethodByName("Baz") == nullptr);
+  EXPECT_TRUE(service2_->FindMethodByName("Bar") == nullptr);
+}
+
+TEST_F(ServiceDescriptorTest, MethodName) {
+  EXPECT_EQ("Foo", foo_->name());
+  EXPECT_EQ("Bar", bar_->name());
+}
+
+TEST_F(ServiceDescriptorTest, MethodFullName) {
+  EXPECT_EQ("TestService.Foo", foo_->full_name());
+  EXPECT_EQ("TestService.Bar", bar_->full_name());
+  EXPECT_EQ("corge.grault.TestService2.Foo", foo2_->full_name());
+  EXPECT_EQ("corge.grault.TestService2.Baz", baz2_->full_name());
+}
+
+TEST_F(ServiceDescriptorTest, MethodIndex) {
+  EXPECT_EQ(0, foo_->index());
+  EXPECT_EQ(1, bar_->index());
+}
+
+TEST_F(ServiceDescriptorTest, MethodParent) {
+  EXPECT_EQ(service_, foo_->service());
+  EXPECT_EQ(service_, bar_->service());
+}
+
+TEST_F(ServiceDescriptorTest, MethodInputType) {
+  EXPECT_EQ(foo_request_, foo_->input_type());
+  EXPECT_EQ(bar_request_, bar_->input_type());
+}
+
+TEST_F(ServiceDescriptorTest, MethodOutputType) {
+  EXPECT_EQ(foo_response_, foo_->output_type());
+  EXPECT_EQ(bar_response_, bar_->output_type());
+}
+
+// ===================================================================
+
+// Test nested types.
+class NestedDescriptorTest : public testing::Test {
+ protected:
+  void SetUp() override {
+    // Build descriptors for the following definitions:
+    //
+    //   // in "foo.proto"
+    //   message TestMessage {
+    //     message Foo {}
+    //     message Bar {}
+    //     enum Baz { A = 1; }
+    //     enum Qux { B = 1; }
+    //   }
+    //
+    //   // in "bar.proto"
+    //   package corge.grault;
+    //   message TestMessage2 {
+    //     message Foo {}
+    //     message Baz {}
+    //     enum Qux  { A = 1; }
+    //     enum Quux { C = 1; }
+    //   }
+    //
+    // TestMessage2 is primarily here to test FindNestedTypeByName and friends.
+    // All messages created from the same DescriptorPool share the same lookup
+    // table, so we need to insure that they don't interfere.
+    //
+    // We add enum values to the enums in order to test searching for enum
+    // values across a message's scope.
+
+    FileDescriptorProto foo_file;
+    foo_file.set_name("foo.proto");
+
+    DescriptorProto* message = AddMessage(&foo_file, "TestMessage");
+    AddNestedMessage(message, "Foo");
+    AddNestedMessage(message, "Bar");
+    EnumDescriptorProto* baz = AddNestedEnum(message, "Baz");
+    AddEnumValue(baz, "A", 1);
+    EnumDescriptorProto* qux = AddNestedEnum(message, "Qux");
+    AddEnumValue(qux, "B", 1);
+
+    FileDescriptorProto bar_file;
+    bar_file.set_name("bar.proto");
+    bar_file.set_package("corge.grault");
+
+    DescriptorProto* message2 = AddMessage(&bar_file, "TestMessage2");
+    AddNestedMessage(message2, "Foo");
+    AddNestedMessage(message2, "Baz");
+    EnumDescriptorProto* qux2 = AddNestedEnum(message2, "Qux");
+    AddEnumValue(qux2, "A", 1);
+    EnumDescriptorProto* quux2 = AddNestedEnum(message2, "Quux");
+    AddEnumValue(quux2, "C", 1);
+
+    // Build the descriptors and get the pointers.
+    foo_file_ = pool_.BuildFile(foo_file);
+    ASSERT_TRUE(foo_file_ != nullptr);
+
+    bar_file_ = pool_.BuildFile(bar_file);
+    ASSERT_TRUE(bar_file_ != nullptr);
+
+    ASSERT_EQ(1, foo_file_->message_type_count());
+    message_ = foo_file_->message_type(0);
+
+    ASSERT_EQ(2, message_->nested_type_count());
+    foo_ = message_->nested_type(0);
+    bar_ = message_->nested_type(1);
+
+    ASSERT_EQ(2, message_->enum_type_count());
+    baz_ = message_->enum_type(0);
+    qux_ = message_->enum_type(1);
+
+    ASSERT_EQ(1, baz_->value_count());
+    a_ = baz_->value(0);
+    ASSERT_EQ(1, qux_->value_count());
+    b_ = qux_->value(0);
+
+    ASSERT_EQ(1, bar_file_->message_type_count());
+    message2_ = bar_file_->message_type(0);
+
+    ASSERT_EQ(2, message2_->nested_type_count());
+    foo2_ = message2_->nested_type(0);
+    baz2_ = message2_->nested_type(1);
+
+    ASSERT_EQ(2, message2_->enum_type_count());
+    qux2_ = message2_->enum_type(0);
+    quux2_ = message2_->enum_type(1);
+
+    ASSERT_EQ(1, qux2_->value_count());
+    a2_ = qux2_->value(0);
+    ASSERT_EQ(1, quux2_->value_count());
+    c2_ = quux2_->value(0);
+  }
+
+  DescriptorPool pool_;
+
+  const FileDescriptor* foo_file_;
+  const FileDescriptor* bar_file_;
+
+  const Descriptor* message_;
+  const Descriptor* message2_;
+
+  const Descriptor* foo_;
+  const Descriptor* bar_;
+  const EnumDescriptor* baz_;
+  const EnumDescriptor* qux_;
+  const EnumValueDescriptor* a_;
+  const EnumValueDescriptor* b_;
+
+  const Descriptor* foo2_;
+  const Descriptor* baz2_;
+  const EnumDescriptor* qux2_;
+  const EnumDescriptor* quux2_;
+  const EnumValueDescriptor* a2_;
+  const EnumValueDescriptor* c2_;
+};
+
+TEST_F(NestedDescriptorTest, MessageName) {
+  EXPECT_EQ("Foo", foo_->name());
+  EXPECT_EQ("Bar", bar_->name());
+  EXPECT_EQ("Foo", foo2_->name());
+  EXPECT_EQ("Baz", baz2_->name());
+
+  EXPECT_EQ("TestMessage.Foo", foo_->full_name());
+  EXPECT_EQ("TestMessage.Bar", bar_->full_name());
+  EXPECT_EQ("corge.grault.TestMessage2.Foo", foo2_->full_name());
+  EXPECT_EQ("corge.grault.TestMessage2.Baz", baz2_->full_name());
+}
+
+TEST_F(NestedDescriptorTest, MessageContainingType) {
+  EXPECT_EQ(message_, foo_->containing_type());
+  EXPECT_EQ(message_, bar_->containing_type());
+  EXPECT_EQ(message2_, foo2_->containing_type());
+  EXPECT_EQ(message2_, baz2_->containing_type());
+}
+
+TEST_F(NestedDescriptorTest, NestedMessagesByIndex) {
+  ASSERT_EQ(2, message_->nested_type_count());
+  EXPECT_EQ(foo_, message_->nested_type(0));
+  EXPECT_EQ(bar_, message_->nested_type(1));
+}
+
+TEST_F(NestedDescriptorTest, FindFieldByNameDoesntFindNestedTypes) {
+  EXPECT_TRUE(message_->FindFieldByName("Foo") == nullptr);
+  EXPECT_TRUE(message_->FindFieldByName("Qux") == nullptr);
+  EXPECT_TRUE(message_->FindExtensionByName("Foo") == nullptr);
+  EXPECT_TRUE(message_->FindExtensionByName("Qux") == nullptr);
+}
+
+TEST_F(NestedDescriptorTest, FindNestedTypeByName) {
+  EXPECT_EQ(foo_, message_->FindNestedTypeByName("Foo"));
+  EXPECT_EQ(bar_, message_->FindNestedTypeByName("Bar"));
+  EXPECT_EQ(foo2_, message2_->FindNestedTypeByName("Foo"));
+  EXPECT_EQ(baz2_, message2_->FindNestedTypeByName("Baz"));
+
+  EXPECT_TRUE(message_->FindNestedTypeByName("NoSuchType") == nullptr);
+  EXPECT_TRUE(message_->FindNestedTypeByName("Baz") == nullptr);
+  EXPECT_TRUE(message2_->FindNestedTypeByName("Bar") == nullptr);
+
+  EXPECT_TRUE(message_->FindNestedTypeByName("Qux") == nullptr);
+}
+
+TEST_F(NestedDescriptorTest, EnumName) {
+  EXPECT_EQ("Baz", baz_->name());
+  EXPECT_EQ("Qux", qux_->name());
+  EXPECT_EQ("Qux", qux2_->name());
+  EXPECT_EQ("Quux", quux2_->name());
+
+  EXPECT_EQ("TestMessage.Baz", baz_->full_name());
+  EXPECT_EQ("TestMessage.Qux", qux_->full_name());
+  EXPECT_EQ("corge.grault.TestMessage2.Qux", qux2_->full_name());
+  EXPECT_EQ("corge.grault.TestMessage2.Quux", quux2_->full_name());
+}
+
+TEST_F(NestedDescriptorTest, EnumContainingType) {
+  EXPECT_EQ(message_, baz_->containing_type());
+  EXPECT_EQ(message_, qux_->containing_type());
+  EXPECT_EQ(message2_, qux2_->containing_type());
+  EXPECT_EQ(message2_, quux2_->containing_type());
+}
+
+TEST_F(NestedDescriptorTest, NestedEnumsByIndex) {
+  ASSERT_EQ(2, message_->nested_type_count());
+  EXPECT_EQ(foo_, message_->nested_type(0));
+  EXPECT_EQ(bar_, message_->nested_type(1));
+}
+
+TEST_F(NestedDescriptorTest, FindEnumTypeByName) {
+  EXPECT_EQ(baz_, message_->FindEnumTypeByName("Baz"));
+  EXPECT_EQ(qux_, message_->FindEnumTypeByName("Qux"));
+  EXPECT_EQ(qux2_, message2_->FindEnumTypeByName("Qux"));
+  EXPECT_EQ(quux2_, message2_->FindEnumTypeByName("Quux"));
+
+  EXPECT_TRUE(message_->FindEnumTypeByName("NoSuchType") == nullptr);
+  EXPECT_TRUE(message_->FindEnumTypeByName("Quux") == nullptr);
+  EXPECT_TRUE(message2_->FindEnumTypeByName("Baz") == nullptr);
+
+  EXPECT_TRUE(message_->FindEnumTypeByName("Foo") == nullptr);
+}
+
+TEST_F(NestedDescriptorTest, FindEnumValueByName) {
+  EXPECT_EQ(a_, message_->FindEnumValueByName("A"));
+  EXPECT_EQ(b_, message_->FindEnumValueByName("B"));
+  EXPECT_EQ(a2_, message2_->FindEnumValueByName("A"));
+  EXPECT_EQ(c2_, message2_->FindEnumValueByName("C"));
+
+  EXPECT_TRUE(message_->FindEnumValueByName("NO_SUCH_VALUE") == nullptr);
+  EXPECT_TRUE(message_->FindEnumValueByName("C") == nullptr);
+  EXPECT_TRUE(message2_->FindEnumValueByName("B") == nullptr);
+
+  EXPECT_TRUE(message_->FindEnumValueByName("Foo") == nullptr);
+}
+
+// ===================================================================
+
+// Test extensions.
+class ExtensionDescriptorTest : public testing::Test {
+ protected:
+  void SetUp() override {
+    // Build descriptors for the following definitions:
+    //
+    //   enum Baz {}
+    //   message Qux {}
+    //
+    //   message Foo {
+    //     extensions 10 to 19;
+    //     extensions 30 to 39;
+    //   }
+    //   extend Foo {
+    //     optional int32 foo_int32 = 10;
+    //   }
+    //   extend Foo {
+    //     repeated TestEnum foo_enum = 19;
+    //   }
+    //   message Bar {
+    //     optional int32 non_ext_int32 = 1;
+    //     extend Foo {
+    //       optional Qux foo_message = 30;
+    //       repeated Qux foo_group = 39;  // (but internally set to TYPE_GROUP)
+    //     }
+    //   }
+
+    FileDescriptorProto foo_file;
+    foo_file.set_name("foo.proto");
+
+    AddEmptyEnum(&foo_file, "Baz");
+    AddMessage(&foo_file, "Qux");
+
+    DescriptorProto* foo = AddMessage(&foo_file, "Foo");
+    AddExtensionRange(foo, 10, 20);
+    AddExtensionRange(foo, 30, 40);
+
+    AddExtension(&foo_file, "Foo", "foo_int32", 10,
+                 FieldDescriptorProto::LABEL_OPTIONAL,
+                 FieldDescriptorProto::TYPE_INT32);
+    AddExtension(&foo_file, "Foo", "foo_enum", 19,
+                 FieldDescriptorProto::LABEL_REPEATED,
+                 FieldDescriptorProto::TYPE_ENUM)
+        ->set_type_name("Baz");
+
+    DescriptorProto* bar = AddMessage(&foo_file, "Bar");
+    AddField(bar, "non_ext_int32", 1, FieldDescriptorProto::LABEL_OPTIONAL,
+             FieldDescriptorProto::TYPE_INT32);
+    AddNestedExtension(bar, "Foo", "foo_message", 30,
+                       FieldDescriptorProto::LABEL_OPTIONAL,
+                       FieldDescriptorProto::TYPE_MESSAGE)
+        ->set_type_name("Qux");
+    AddNestedExtension(bar, "Foo", "foo_group", 39,
+                       FieldDescriptorProto::LABEL_REPEATED,
+                       FieldDescriptorProto::TYPE_GROUP)
+        ->set_type_name("Qux");
+
+    // Build the descriptors and get the pointers.
+    foo_file_ = pool_.BuildFile(foo_file);
+    ASSERT_TRUE(foo_file_ != nullptr);
+
+    ASSERT_EQ(1, foo_file_->enum_type_count());
+    baz_ = foo_file_->enum_type(0);
+
+    ASSERT_EQ(3, foo_file_->message_type_count());
+    qux_ = foo_file_->message_type(0);
+    foo_ = foo_file_->message_type(1);
+    bar_ = foo_file_->message_type(2);
+  }
+
+  DescriptorPool pool_;
+
+  const FileDescriptor* foo_file_;
+
+  const Descriptor* foo_;
+  const Descriptor* bar_;
+  const EnumDescriptor* baz_;
+  const Descriptor* qux_;
+};
+
+TEST_F(ExtensionDescriptorTest, ExtensionRanges) {
+  EXPECT_EQ(0, bar_->extension_range_count());
+  ASSERT_EQ(2, foo_->extension_range_count());
+
+  EXPECT_EQ(10, foo_->extension_range(0)->start);
+  EXPECT_EQ(30, foo_->extension_range(1)->start);
+
+  EXPECT_EQ(20, foo_->extension_range(0)->end);
+  EXPECT_EQ(40, foo_->extension_range(1)->end);
+}
+
+TEST_F(ExtensionDescriptorTest, Extensions) {
+  EXPECT_EQ(0, foo_->extension_count());
+  ASSERT_EQ(2, foo_file_->extension_count());
+  ASSERT_EQ(2, bar_->extension_count());
+
+  EXPECT_TRUE(foo_file_->extension(0)->is_extension());
+  EXPECT_TRUE(foo_file_->extension(1)->is_extension());
+  EXPECT_TRUE(bar_->extension(0)->is_extension());
+  EXPECT_TRUE(bar_->extension(1)->is_extension());
+
+  EXPECT_EQ("foo_int32", foo_file_->extension(0)->name());
+  EXPECT_EQ("foo_enum", foo_file_->extension(1)->name());
+  EXPECT_EQ("foo_message", bar_->extension(0)->name());
+  EXPECT_EQ("foo_group", bar_->extension(1)->name());
+
+  EXPECT_EQ(10, foo_file_->extension(0)->number());
+  EXPECT_EQ(19, foo_file_->extension(1)->number());
+  EXPECT_EQ(30, bar_->extension(0)->number());
+  EXPECT_EQ(39, bar_->extension(1)->number());
+
+  EXPECT_EQ(FieldDescriptor::TYPE_INT32, foo_file_->extension(0)->type());
+  EXPECT_EQ(FieldDescriptor::TYPE_ENUM, foo_file_->extension(1)->type());
+  EXPECT_EQ(FieldDescriptor::TYPE_MESSAGE, bar_->extension(0)->type());
+  EXPECT_EQ(FieldDescriptor::TYPE_GROUP, bar_->extension(1)->type());
+
+  EXPECT_EQ(baz_, foo_file_->extension(1)->enum_type());
+  EXPECT_EQ(qux_, bar_->extension(0)->message_type());
+  EXPECT_EQ(qux_, bar_->extension(1)->message_type());
+
+  EXPECT_EQ(FieldDescriptor::LABEL_OPTIONAL, foo_file_->extension(0)->label());
+  EXPECT_EQ(FieldDescriptor::LABEL_REPEATED, foo_file_->extension(1)->label());
+  EXPECT_EQ(FieldDescriptor::LABEL_OPTIONAL, bar_->extension(0)->label());
+  EXPECT_EQ(FieldDescriptor::LABEL_REPEATED, bar_->extension(1)->label());
+
+  EXPECT_EQ(foo_, foo_file_->extension(0)->containing_type());
+  EXPECT_EQ(foo_, foo_file_->extension(1)->containing_type());
+  EXPECT_EQ(foo_, bar_->extension(0)->containing_type());
+  EXPECT_EQ(foo_, bar_->extension(1)->containing_type());
+
+  EXPECT_TRUE(foo_file_->extension(0)->extension_scope() == nullptr);
+  EXPECT_TRUE(foo_file_->extension(1)->extension_scope() == nullptr);
+  EXPECT_EQ(bar_, bar_->extension(0)->extension_scope());
+  EXPECT_EQ(bar_, bar_->extension(1)->extension_scope());
+}
+
+TEST_F(ExtensionDescriptorTest, IsExtensionNumber) {
+  EXPECT_FALSE(foo_->IsExtensionNumber(9));
+  EXPECT_TRUE(foo_->IsExtensionNumber(10));
+  EXPECT_TRUE(foo_->IsExtensionNumber(19));
+  EXPECT_FALSE(foo_->IsExtensionNumber(20));
+  EXPECT_FALSE(foo_->IsExtensionNumber(29));
+  EXPECT_TRUE(foo_->IsExtensionNumber(30));
+  EXPECT_TRUE(foo_->IsExtensionNumber(39));
+  EXPECT_FALSE(foo_->IsExtensionNumber(40));
+}
+
+TEST_F(ExtensionDescriptorTest, FindExtensionByName) {
+  // Note that FileDescriptor::FindExtensionByName() is tested by
+  // FileDescriptorTest.
+  ASSERT_EQ(2, bar_->extension_count());
+
+  EXPECT_EQ(bar_->extension(0), bar_->FindExtensionByName("foo_message"));
+  EXPECT_EQ(bar_->extension(1), bar_->FindExtensionByName("foo_group"));
+
+  EXPECT_TRUE(bar_->FindExtensionByName("no_such_extension") == nullptr);
+  EXPECT_TRUE(foo_->FindExtensionByName("foo_int32") == nullptr);
+  EXPECT_TRUE(foo_->FindExtensionByName("foo_message") == nullptr);
+}
+
+TEST_F(ExtensionDescriptorTest, FieldVsExtension) {
+  EXPECT_EQ(foo_->FindFieldByName("foo_message"), nullptr);
+  EXPECT_EQ(bar_->FindFieldByName("foo_message"), nullptr);
+  EXPECT_NE(bar_->FindFieldByName("non_ext_int32"), nullptr);
+  EXPECT_EQ(foo_->FindExtensionByName("foo_message"), nullptr);
+  EXPECT_NE(bar_->FindExtensionByName("foo_message"), nullptr);
+  EXPECT_EQ(bar_->FindExtensionByName("non_ext_int32"), nullptr);
+}
+
+TEST_F(ExtensionDescriptorTest, FindExtensionByPrintableName) {
+  EXPECT_TRUE(pool_.FindExtensionByPrintableName(foo_, "no_such_extension") ==
+              nullptr);
+  EXPECT_TRUE(pool_.FindExtensionByPrintableName(bar_, "no_such_extension") ==
+              nullptr);
+
+  ASSERT_FALSE(pool_.FindExtensionByPrintableName(foo_, "Bar.foo_message") ==
+               nullptr);
+  ASSERT_FALSE(pool_.FindExtensionByPrintableName(foo_, "Bar.foo_group") ==
+               nullptr);
+  EXPECT_TRUE(pool_.FindExtensionByPrintableName(bar_, "foo_message") ==
+              nullptr);
+  EXPECT_TRUE(pool_.FindExtensionByPrintableName(bar_, "foo_group") == nullptr);
+  EXPECT_EQ(bar_->FindExtensionByName("foo_message"),
+            pool_.FindExtensionByPrintableName(foo_, "Bar.foo_message"));
+  EXPECT_EQ(bar_->FindExtensionByName("foo_group"),
+            pool_.FindExtensionByPrintableName(foo_, "Bar.foo_group"));
+
+  ASSERT_FALSE(pool_.FindExtensionByPrintableName(foo_, "foo_int32") ==
+               nullptr);
+  ASSERT_FALSE(pool_.FindExtensionByPrintableName(foo_, "foo_enum") == nullptr);
+  EXPECT_TRUE(pool_.FindExtensionByPrintableName(bar_, "foo_int32") == nullptr);
+  EXPECT_TRUE(pool_.FindExtensionByPrintableName(bar_, "foo_enum") == nullptr);
+  EXPECT_EQ(foo_file_->FindExtensionByName("foo_int32"),
+            pool_.FindExtensionByPrintableName(foo_, "foo_int32"));
+  EXPECT_EQ(foo_file_->FindExtensionByName("foo_enum"),
+            pool_.FindExtensionByPrintableName(foo_, "foo_enum"));
+}
+
+TEST_F(ExtensionDescriptorTest, FindAllExtensions) {
+  std::vector<const FieldDescriptor*> extensions;
+  pool_.FindAllExtensions(foo_, &extensions);
+  ASSERT_EQ(4, extensions.size());
+  EXPECT_EQ(10, extensions[0]->number());
+  EXPECT_EQ(19, extensions[1]->number());
+  EXPECT_EQ(30, extensions[2]->number());
+  EXPECT_EQ(39, extensions[3]->number());
+}
+
+
+TEST_F(ExtensionDescriptorTest, DuplicateFieldNumber) {
+  DescriptorPool pool;
+  FileDescriptorProto file_proto;
+  // Add "google/protobuf/descriptor.proto".
+  FileDescriptorProto::descriptor()->file()->CopyTo(&file_proto);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+  // Add "foo.proto":
+  //   import "google/protobuf/descriptor.proto";
+  //   extend google.protobuf.FieldOptions {
+  //     optional int32 option1 = 1000;
+  //   }
+  file_proto.Clear();
+  file_proto.set_name("foo.proto");
+  file_proto.add_dependency("google/protobuf/descriptor.proto");
+  AddExtension(&file_proto, "google.protobuf.FieldOptions", "option1", 1000,
+               FieldDescriptorProto::LABEL_OPTIONAL,
+               FieldDescriptorProto::TYPE_INT32);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+  // Add "bar.proto":
+  //   import "google/protobuf/descriptor.proto";
+  //   extend google.protobuf.FieldOptions {
+  //     optional int32 option2 = 1000;
+  //   }
+  file_proto.Clear();
+  file_proto.set_name("bar.proto");
+  file_proto.add_dependency("google/protobuf/descriptor.proto");
+  AddExtension(&file_proto, "google.protobuf.FieldOptions", "option2", 1000,
+               FieldDescriptorProto::LABEL_OPTIONAL,
+               FieldDescriptorProto::TYPE_INT32);
+  // Currently we only generate a warning for conflicting extension numbers.
+  // TODO(xiaofeng): Change it to an error.
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+}
+
+// ===================================================================
+
+// Ensure that overlapping extension ranges are not allowed.
+TEST(OverlappingExtensionRangeTest, ExtensionRangeInternal) {
+  // Build descriptors for the following definitions:
+  //
+  //   message Foo {
+  //     extensions 10 to 19;
+  //     extensions 15;
+  //   }
+  FileDescriptorProto foo_file;
+  foo_file.set_name("foo.proto");
+
+  DescriptorProto* foo = AddMessage(&foo_file, "Foo");
+  AddExtensionRange(foo, 10, 20);
+  AddExtensionRange(foo, 15, 16);
+
+  DescriptorPool pool;
+  MockErrorCollector error_collector;
+  // The extensions ranges are invalid, so the proto shouldn't build.
+  ASSERT_TRUE(pool.BuildFileCollectingErrors(foo_file, &error_collector) ==
+              nullptr);
+  ASSERT_EQ(
+      "foo.proto: Foo: NUMBER: Extension range 15 to 15 overlaps with "
+      "already-defined range 10 to 19.\n",
+      error_collector.text_);
+}
+
+TEST(OverlappingExtensionRangeTest, ExtensionRangeAfter) {
+  // Build descriptors for the following definitions:
+  //
+  //   message Foo {
+  //     extensions 10 to 19;
+  //     extensions 15 to 24;
+  //   }
+  FileDescriptorProto foo_file;
+  foo_file.set_name("foo.proto");
+
+  DescriptorProto* foo = AddMessage(&foo_file, "Foo");
+  AddExtensionRange(foo, 10, 20);
+  AddExtensionRange(foo, 15, 25);
+
+  DescriptorPool pool;
+  MockErrorCollector error_collector;
+  // The extensions ranges are invalid, so the proto shouldn't build.
+  ASSERT_TRUE(pool.BuildFileCollectingErrors(foo_file, &error_collector) ==
+              nullptr);
+  ASSERT_EQ(
+      "foo.proto: Foo: NUMBER: Extension range 15 to 24 overlaps with "
+      "already-defined range 10 to 19.\n",
+      error_collector.text_);
+}
+
+TEST(OverlappingExtensionRangeTest, ExtensionRangeBefore) {
+  // Build descriptors for the following definitions:
+  //
+  //   message Foo {
+  //     extensions 10 to 19;
+  //     extensions 5 to 14;
+  //   }
+  FileDescriptorProto foo_file;
+  foo_file.set_name("foo.proto");
+
+  DescriptorProto* foo = AddMessage(&foo_file, "Foo");
+  AddExtensionRange(foo, 10, 20);
+  AddExtensionRange(foo, 5, 15);
+
+  DescriptorPool pool;
+  MockErrorCollector error_collector;
+  // The extensions ranges are invalid, so the proto shouldn't build.
+  ASSERT_TRUE(pool.BuildFileCollectingErrors(foo_file, &error_collector) ==
+              nullptr);
+  ASSERT_EQ(
+      "foo.proto: Foo: NUMBER: Extension range 5 to 14 overlaps with "
+      "already-defined range 10 to 19.\n",
+      error_collector.text_);
+}
+
+// ===================================================================
+
+// Test reserved fields.
+class ReservedDescriptorTest : public testing::Test {
+ protected:
+  void SetUp() override {
+    // Build descriptors for the following definitions:
+    //
+    //   message Foo {
+    //     reserved 2, 9 to 11, 15;
+    //     reserved "foo", "bar";
+    //   }
+
+    FileDescriptorProto foo_file;
+    foo_file.set_name("foo.proto");
+
+    DescriptorProto* foo = AddMessage(&foo_file, "Foo");
+    AddReservedRange(foo, 2, 3);
+    AddReservedRange(foo, 9, 12);
+    AddReservedRange(foo, 15, 16);
+
+    foo->add_reserved_name("foo");
+    foo->add_reserved_name("bar");
+
+    // Build the descriptors and get the pointers.
+    foo_file_ = pool_.BuildFile(foo_file);
+    ASSERT_TRUE(foo_file_ != nullptr);
+
+    ASSERT_EQ(1, foo_file_->message_type_count());
+    foo_ = foo_file_->message_type(0);
+  }
+
+  DescriptorPool pool_;
+  const FileDescriptor* foo_file_;
+  const Descriptor* foo_;
+};
+
+TEST_F(ReservedDescriptorTest, ReservedRanges) {
+  ASSERT_EQ(3, foo_->reserved_range_count());
+
+  EXPECT_EQ(2, foo_->reserved_range(0)->start);
+  EXPECT_EQ(3, foo_->reserved_range(0)->end);
+
+  EXPECT_EQ(9, foo_->reserved_range(1)->start);
+  EXPECT_EQ(12, foo_->reserved_range(1)->end);
+
+  EXPECT_EQ(15, foo_->reserved_range(2)->start);
+  EXPECT_EQ(16, foo_->reserved_range(2)->end);
+}
+
+TEST_F(ReservedDescriptorTest, IsReservedNumber) {
+  EXPECT_FALSE(foo_->IsReservedNumber(1));
+  EXPECT_TRUE(foo_->IsReservedNumber(2));
+  EXPECT_FALSE(foo_->IsReservedNumber(3));
+  EXPECT_FALSE(foo_->IsReservedNumber(8));
+  EXPECT_TRUE(foo_->IsReservedNumber(9));
+  EXPECT_TRUE(foo_->IsReservedNumber(10));
+  EXPECT_TRUE(foo_->IsReservedNumber(11));
+  EXPECT_FALSE(foo_->IsReservedNumber(12));
+  EXPECT_FALSE(foo_->IsReservedNumber(13));
+  EXPECT_FALSE(foo_->IsReservedNumber(14));
+  EXPECT_TRUE(foo_->IsReservedNumber(15));
+  EXPECT_FALSE(foo_->IsReservedNumber(16));
+}
+
+TEST_F(ReservedDescriptorTest, ReservedNames) {
+  ASSERT_EQ(2, foo_->reserved_name_count());
+
+  EXPECT_EQ("foo", foo_->reserved_name(0));
+  EXPECT_EQ("bar", foo_->reserved_name(1));
+}
+
+TEST_F(ReservedDescriptorTest, IsReservedName) {
+  EXPECT_TRUE(foo_->IsReservedName("foo"));
+  EXPECT_TRUE(foo_->IsReservedName("bar"));
+  EXPECT_FALSE(foo_->IsReservedName("baz"));
+}
+
+// ===================================================================
+
+// Test reserved enum fields.
+class ReservedEnumDescriptorTest : public testing::Test {
+ protected:
+  void SetUp() override {
+    // Build descriptors for the following definitions:
+    //
+    //   enum Foo {
+    //     BAR = 1;
+    //     reserved 2, 9 to 11, 15;
+    //     reserved "foo", "bar";
+    //   }
+
+    FileDescriptorProto foo_file;
+    foo_file.set_name("foo.proto");
+
+    EnumDescriptorProto* foo = AddEnum(&foo_file, "Foo");
+    EnumDescriptorProto* edge1 = AddEnum(&foo_file, "Edge1");
+    EnumDescriptorProto* edge2 = AddEnum(&foo_file, "Edge2");
+
+    AddEnumValue(foo, "BAR", 4);
+    AddReservedRange(foo, -5, -3);
+    AddReservedRange(foo, -2, 1);
+    AddReservedRange(foo, 2, 3);
+    AddReservedRange(foo, 9, 12);
+    AddReservedRange(foo, 15, 16);
+
+    foo->add_reserved_name("foo");
+    foo->add_reserved_name("bar");
+
+    // Some additional edge cases that cover most or all of the range of enum
+    // values
+
+    // Note: We use INT_MAX as the maximum reserved range upper bound,
+    // inclusive.
+    AddEnumValue(edge1, "EDGE1", 1);
+    AddReservedRange(edge1, 10, INT_MAX);
+    AddEnumValue(edge2, "EDGE2", 15);
+    AddReservedRange(edge2, INT_MIN, 10);
+
+    // Build the descriptors and get the pointers.
+    foo_file_ = pool_.BuildFile(foo_file);
+    ASSERT_TRUE(foo_file_ != nullptr);
+
+    ASSERT_EQ(3, foo_file_->enum_type_count());
+    foo_ = foo_file_->enum_type(0);
+    edge1_ = foo_file_->enum_type(1);
+    edge2_ = foo_file_->enum_type(2);
+  }
+
+  DescriptorPool pool_;
+  const FileDescriptor* foo_file_;
+  const EnumDescriptor* foo_;
+  const EnumDescriptor* edge1_;
+  const EnumDescriptor* edge2_;
+};
+
+TEST_F(ReservedEnumDescriptorTest, ReservedRanges) {
+  ASSERT_EQ(5, foo_->reserved_range_count());
+
+  EXPECT_EQ(-5, foo_->reserved_range(0)->start);
+  EXPECT_EQ(-3, foo_->reserved_range(0)->end);
+
+  EXPECT_EQ(-2, foo_->reserved_range(1)->start);
+  EXPECT_EQ(1, foo_->reserved_range(1)->end);
+
+  EXPECT_EQ(2, foo_->reserved_range(2)->start);
+  EXPECT_EQ(3, foo_->reserved_range(2)->end);
+
+  EXPECT_EQ(9, foo_->reserved_range(3)->start);
+  EXPECT_EQ(12, foo_->reserved_range(3)->end);
+
+  EXPECT_EQ(15, foo_->reserved_range(4)->start);
+  EXPECT_EQ(16, foo_->reserved_range(4)->end);
+
+  ASSERT_EQ(1, edge1_->reserved_range_count());
+  EXPECT_EQ(10, edge1_->reserved_range(0)->start);
+  EXPECT_EQ(INT_MAX, edge1_->reserved_range(0)->end);
+
+  ASSERT_EQ(1, edge2_->reserved_range_count());
+  EXPECT_EQ(INT_MIN, edge2_->reserved_range(0)->start);
+  EXPECT_EQ(10, edge2_->reserved_range(0)->end);
+}
+
+TEST_F(ReservedEnumDescriptorTest, IsReservedNumber) {
+  EXPECT_TRUE(foo_->IsReservedNumber(-5));
+  EXPECT_TRUE(foo_->IsReservedNumber(-4));
+  EXPECT_TRUE(foo_->IsReservedNumber(-3));
+  EXPECT_TRUE(foo_->IsReservedNumber(-2));
+  EXPECT_TRUE(foo_->IsReservedNumber(-1));
+  EXPECT_TRUE(foo_->IsReservedNumber(0));
+  EXPECT_TRUE(foo_->IsReservedNumber(1));
+  EXPECT_TRUE(foo_->IsReservedNumber(2));
+  EXPECT_TRUE(foo_->IsReservedNumber(3));
+  EXPECT_FALSE(foo_->IsReservedNumber(8));
+  EXPECT_TRUE(foo_->IsReservedNumber(9));
+  EXPECT_TRUE(foo_->IsReservedNumber(10));
+  EXPECT_TRUE(foo_->IsReservedNumber(11));
+  EXPECT_TRUE(foo_->IsReservedNumber(12));
+  EXPECT_FALSE(foo_->IsReservedNumber(13));
+  EXPECT_FALSE(foo_->IsReservedNumber(13));
+  EXPECT_FALSE(foo_->IsReservedNumber(14));
+  EXPECT_TRUE(foo_->IsReservedNumber(15));
+  EXPECT_TRUE(foo_->IsReservedNumber(16));
+  EXPECT_FALSE(foo_->IsReservedNumber(17));
+
+  EXPECT_FALSE(edge1_->IsReservedNumber(9));
+  EXPECT_TRUE(edge1_->IsReservedNumber(10));
+  EXPECT_TRUE(edge1_->IsReservedNumber(INT_MAX - 1));
+  EXPECT_TRUE(edge1_->IsReservedNumber(INT_MAX));
+
+  EXPECT_TRUE(edge2_->IsReservedNumber(INT_MIN));
+  EXPECT_TRUE(edge2_->IsReservedNumber(9));
+  EXPECT_TRUE(edge2_->IsReservedNumber(10));
+  EXPECT_FALSE(edge2_->IsReservedNumber(11));
+}
+
+TEST_F(ReservedEnumDescriptorTest, ReservedNames) {
+  ASSERT_EQ(2, foo_->reserved_name_count());
+
+  EXPECT_EQ("foo", foo_->reserved_name(0));
+  EXPECT_EQ("bar", foo_->reserved_name(1));
+}
+
+TEST_F(ReservedEnumDescriptorTest, IsReservedName) {
+  EXPECT_TRUE(foo_->IsReservedName("foo"));
+  EXPECT_TRUE(foo_->IsReservedName("bar"));
+  EXPECT_FALSE(foo_->IsReservedName("baz"));
+}
+
+// ===================================================================
+
+class MiscTest : public testing::Test {
+ protected:
+  // Function which makes a field descriptor of the given type.
+  const FieldDescriptor* GetFieldDescriptorOfType(FieldDescriptor::Type type) {
+    FileDescriptorProto file_proto;
+    file_proto.set_name("foo.proto");
+    AddEmptyEnum(&file_proto, "DummyEnum");
+
+    DescriptorProto* message = AddMessage(&file_proto, "TestMessage");
+    FieldDescriptorProto* field = AddField(
+        message, "foo", 1, FieldDescriptorProto::LABEL_OPTIONAL,
+        static_cast<FieldDescriptorProto::Type>(static_cast<int>(type)));
+
+    if (type == FieldDescriptor::TYPE_MESSAGE ||
+        type == FieldDescriptor::TYPE_GROUP) {
+      field->set_type_name("TestMessage");
+    } else if (type == FieldDescriptor::TYPE_ENUM) {
+      field->set_type_name("DummyEnum");
+    }
+
+    // Build the descriptors and get the pointers.
+    pool_.reset(new DescriptorPool());
+    const FileDescriptor* file = pool_->BuildFile(file_proto);
+
+    if (file != nullptr && file->message_type_count() == 1 &&
+        file->message_type(0)->field_count() == 1) {
+      return file->message_type(0)->field(0);
+    } else {
+      return nullptr;
+    }
+  }
+
+  const char* GetTypeNameForFieldType(FieldDescriptor::Type type) {
+    const FieldDescriptor* field = GetFieldDescriptorOfType(type);
+    return field != nullptr ? field->type_name() : "";
+  }
+
+  FieldDescriptor::CppType GetCppTypeForFieldType(FieldDescriptor::Type type) {
+    const FieldDescriptor* field = GetFieldDescriptorOfType(type);
+    return field != nullptr ? field->cpp_type()
+                            : static_cast<FieldDescriptor::CppType>(0);
+  }
+
+  const char* GetCppTypeNameForFieldType(FieldDescriptor::Type type) {
+    const FieldDescriptor* field = GetFieldDescriptorOfType(type);
+    return field != nullptr ? field->cpp_type_name() : "";
+  }
+
+  const Descriptor* GetMessageDescriptorForFieldType(
+      FieldDescriptor::Type type) {
+    const FieldDescriptor* field = GetFieldDescriptorOfType(type);
+    return field != nullptr ? field->message_type() : nullptr;
+  }
+
+  const EnumDescriptor* GetEnumDescriptorForFieldType(
+      FieldDescriptor::Type type) {
+    const FieldDescriptor* field = GetFieldDescriptorOfType(type);
+    return field != nullptr ? field->enum_type() : nullptr;
+  }
+
+  std::unique_ptr<DescriptorPool> pool_;
+};
+
+TEST_F(MiscTest, TypeNames) {
+  // Test that correct type names are returned.
+
+  typedef FieldDescriptor FD;  // avoid ugly line wrapping
+
+  EXPECT_STREQ("double", GetTypeNameForFieldType(FD::TYPE_DOUBLE));
+  EXPECT_STREQ("float", GetTypeNameForFieldType(FD::TYPE_FLOAT));
+  EXPECT_STREQ("int64", GetTypeNameForFieldType(FD::TYPE_INT64));
+  EXPECT_STREQ("uint64", GetTypeNameForFieldType(FD::TYPE_UINT64));
+  EXPECT_STREQ("int32", GetTypeNameForFieldType(FD::TYPE_INT32));
+  EXPECT_STREQ("fixed64", GetTypeNameForFieldType(FD::TYPE_FIXED64));
+  EXPECT_STREQ("fixed32", GetTypeNameForFieldType(FD::TYPE_FIXED32));
+  EXPECT_STREQ("bool", GetTypeNameForFieldType(FD::TYPE_BOOL));
+  EXPECT_STREQ("string", GetTypeNameForFieldType(FD::TYPE_STRING));
+  EXPECT_STREQ("group", GetTypeNameForFieldType(FD::TYPE_GROUP));
+  EXPECT_STREQ("message", GetTypeNameForFieldType(FD::TYPE_MESSAGE));
+  EXPECT_STREQ("bytes", GetTypeNameForFieldType(FD::TYPE_BYTES));
+  EXPECT_STREQ("uint32", GetTypeNameForFieldType(FD::TYPE_UINT32));
+  EXPECT_STREQ("enum", GetTypeNameForFieldType(FD::TYPE_ENUM));
+  EXPECT_STREQ("sfixed32", GetTypeNameForFieldType(FD::TYPE_SFIXED32));
+  EXPECT_STREQ("sfixed64", GetTypeNameForFieldType(FD::TYPE_SFIXED64));
+  EXPECT_STREQ("sint32", GetTypeNameForFieldType(FD::TYPE_SINT32));
+  EXPECT_STREQ("sint64", GetTypeNameForFieldType(FD::TYPE_SINT64));
+}
+
+TEST_F(MiscTest, StaticTypeNames) {
+  // Test that correct type names are returned.
+
+  typedef FieldDescriptor FD;  // avoid ugly line wrapping
+
+  EXPECT_STREQ("double", FD::TypeName(FD::TYPE_DOUBLE));
+  EXPECT_STREQ("float", FD::TypeName(FD::TYPE_FLOAT));
+  EXPECT_STREQ("int64", FD::TypeName(FD::TYPE_INT64));
+  EXPECT_STREQ("uint64", FD::TypeName(FD::TYPE_UINT64));
+  EXPECT_STREQ("int32", FD::TypeName(FD::TYPE_INT32));
+  EXPECT_STREQ("fixed64", FD::TypeName(FD::TYPE_FIXED64));
+  EXPECT_STREQ("fixed32", FD::TypeName(FD::TYPE_FIXED32));
+  EXPECT_STREQ("bool", FD::TypeName(FD::TYPE_BOOL));
+  EXPECT_STREQ("string", FD::TypeName(FD::TYPE_STRING));
+  EXPECT_STREQ("group", FD::TypeName(FD::TYPE_GROUP));
+  EXPECT_STREQ("message", FD::TypeName(FD::TYPE_MESSAGE));
+  EXPECT_STREQ("bytes", FD::TypeName(FD::TYPE_BYTES));
+  EXPECT_STREQ("uint32", FD::TypeName(FD::TYPE_UINT32));
+  EXPECT_STREQ("enum", FD::TypeName(FD::TYPE_ENUM));
+  EXPECT_STREQ("sfixed32", FD::TypeName(FD::TYPE_SFIXED32));
+  EXPECT_STREQ("sfixed64", FD::TypeName(FD::TYPE_SFIXED64));
+  EXPECT_STREQ("sint32", FD::TypeName(FD::TYPE_SINT32));
+  EXPECT_STREQ("sint64", FD::TypeName(FD::TYPE_SINT64));
+}
+
+TEST_F(MiscTest, CppTypes) {
+  // Test that CPP types are assigned correctly.
+
+  typedef FieldDescriptor FD;  // avoid ugly line wrapping
+
+  EXPECT_EQ(FD::CPPTYPE_DOUBLE, GetCppTypeForFieldType(FD::TYPE_DOUBLE));
+  EXPECT_EQ(FD::CPPTYPE_FLOAT, GetCppTypeForFieldType(FD::TYPE_FLOAT));
+  EXPECT_EQ(FD::CPPTYPE_INT64, GetCppTypeForFieldType(FD::TYPE_INT64));
+  EXPECT_EQ(FD::CPPTYPE_UINT64, GetCppTypeForFieldType(FD::TYPE_UINT64));
+  EXPECT_EQ(FD::CPPTYPE_INT32, GetCppTypeForFieldType(FD::TYPE_INT32));
+  EXPECT_EQ(FD::CPPTYPE_UINT64, GetCppTypeForFieldType(FD::TYPE_FIXED64));
+  EXPECT_EQ(FD::CPPTYPE_UINT32, GetCppTypeForFieldType(FD::TYPE_FIXED32));
+  EXPECT_EQ(FD::CPPTYPE_BOOL, GetCppTypeForFieldType(FD::TYPE_BOOL));
+  EXPECT_EQ(FD::CPPTYPE_STRING, GetCppTypeForFieldType(FD::TYPE_STRING));
+  EXPECT_EQ(FD::CPPTYPE_MESSAGE, GetCppTypeForFieldType(FD::TYPE_GROUP));
+  EXPECT_EQ(FD::CPPTYPE_MESSAGE, GetCppTypeForFieldType(FD::TYPE_MESSAGE));
+  EXPECT_EQ(FD::CPPTYPE_STRING, GetCppTypeForFieldType(FD::TYPE_BYTES));
+  EXPECT_EQ(FD::CPPTYPE_UINT32, GetCppTypeForFieldType(FD::TYPE_UINT32));
+  EXPECT_EQ(FD::CPPTYPE_ENUM, GetCppTypeForFieldType(FD::TYPE_ENUM));
+  EXPECT_EQ(FD::CPPTYPE_INT32, GetCppTypeForFieldType(FD::TYPE_SFIXED32));
+  EXPECT_EQ(FD::CPPTYPE_INT64, GetCppTypeForFieldType(FD::TYPE_SFIXED64));
+  EXPECT_EQ(FD::CPPTYPE_INT32, GetCppTypeForFieldType(FD::TYPE_SINT32));
+  EXPECT_EQ(FD::CPPTYPE_INT64, GetCppTypeForFieldType(FD::TYPE_SINT64));
+}
+
+TEST_F(MiscTest, CppTypeNames) {
+  // Test that correct CPP type names are returned.
+
+  typedef FieldDescriptor FD;  // avoid ugly line wrapping
+
+  EXPECT_STREQ("double", GetCppTypeNameForFieldType(FD::TYPE_DOUBLE));
+  EXPECT_STREQ("float", GetCppTypeNameForFieldType(FD::TYPE_FLOAT));
+  EXPECT_STREQ("int64", GetCppTypeNameForFieldType(FD::TYPE_INT64));
+  EXPECT_STREQ("uint64", GetCppTypeNameForFieldType(FD::TYPE_UINT64));
+  EXPECT_STREQ("int32", GetCppTypeNameForFieldType(FD::TYPE_INT32));
+  EXPECT_STREQ("uint64", GetCppTypeNameForFieldType(FD::TYPE_FIXED64));
+  EXPECT_STREQ("uint32", GetCppTypeNameForFieldType(FD::TYPE_FIXED32));
+  EXPECT_STREQ("bool", GetCppTypeNameForFieldType(FD::TYPE_BOOL));
+  EXPECT_STREQ("string", GetCppTypeNameForFieldType(FD::TYPE_STRING));
+  EXPECT_STREQ("message", GetCppTypeNameForFieldType(FD::TYPE_GROUP));
+  EXPECT_STREQ("message", GetCppTypeNameForFieldType(FD::TYPE_MESSAGE));
+  EXPECT_STREQ("string", GetCppTypeNameForFieldType(FD::TYPE_BYTES));
+  EXPECT_STREQ("uint32", GetCppTypeNameForFieldType(FD::TYPE_UINT32));
+  EXPECT_STREQ("enum", GetCppTypeNameForFieldType(FD::TYPE_ENUM));
+  EXPECT_STREQ("int32", GetCppTypeNameForFieldType(FD::TYPE_SFIXED32));
+  EXPECT_STREQ("int64", GetCppTypeNameForFieldType(FD::TYPE_SFIXED64));
+  EXPECT_STREQ("int32", GetCppTypeNameForFieldType(FD::TYPE_SINT32));
+  EXPECT_STREQ("int64", GetCppTypeNameForFieldType(FD::TYPE_SINT64));
+}
+
+TEST_F(MiscTest, StaticCppTypeNames) {
+  // Test that correct CPP type names are returned.
+
+  typedef FieldDescriptor FD;  // avoid ugly line wrapping
+
+  EXPECT_STREQ("int32", FD::CppTypeName(FD::CPPTYPE_INT32));
+  EXPECT_STREQ("int64", FD::CppTypeName(FD::CPPTYPE_INT64));
+  EXPECT_STREQ("uint32", FD::CppTypeName(FD::CPPTYPE_UINT32));
+  EXPECT_STREQ("uint64", FD::CppTypeName(FD::CPPTYPE_UINT64));
+  EXPECT_STREQ("double", FD::CppTypeName(FD::CPPTYPE_DOUBLE));
+  EXPECT_STREQ("float", FD::CppTypeName(FD::CPPTYPE_FLOAT));
+  EXPECT_STREQ("bool", FD::CppTypeName(FD::CPPTYPE_BOOL));
+  EXPECT_STREQ("enum", FD::CppTypeName(FD::CPPTYPE_ENUM));
+  EXPECT_STREQ("string", FD::CppTypeName(FD::CPPTYPE_STRING));
+  EXPECT_STREQ("message", FD::CppTypeName(FD::CPPTYPE_MESSAGE));
+}
+
+TEST_F(MiscTest, MessageType) {
+  // Test that message_type() is nullptr for non-aggregate fields
+
+  typedef FieldDescriptor FD;  // avoid ugly line wrapping
+
+  EXPECT_TRUE(nullptr == GetMessageDescriptorForFieldType(FD::TYPE_DOUBLE));
+  EXPECT_TRUE(nullptr == GetMessageDescriptorForFieldType(FD::TYPE_FLOAT));
+  EXPECT_TRUE(nullptr == GetMessageDescriptorForFieldType(FD::TYPE_INT64));
+  EXPECT_TRUE(nullptr == GetMessageDescriptorForFieldType(FD::TYPE_UINT64));
+  EXPECT_TRUE(nullptr == GetMessageDescriptorForFieldType(FD::TYPE_INT32));
+  EXPECT_TRUE(nullptr == GetMessageDescriptorForFieldType(FD::TYPE_FIXED64));
+  EXPECT_TRUE(nullptr == GetMessageDescriptorForFieldType(FD::TYPE_FIXED32));
+  EXPECT_TRUE(nullptr == GetMessageDescriptorForFieldType(FD::TYPE_BOOL));
+  EXPECT_TRUE(nullptr == GetMessageDescriptorForFieldType(FD::TYPE_STRING));
+  EXPECT_TRUE(nullptr != GetMessageDescriptorForFieldType(FD::TYPE_GROUP));
+  EXPECT_TRUE(nullptr != GetMessageDescriptorForFieldType(FD::TYPE_MESSAGE));
+  EXPECT_TRUE(nullptr == GetMessageDescriptorForFieldType(FD::TYPE_BYTES));
+  EXPECT_TRUE(nullptr == GetMessageDescriptorForFieldType(FD::TYPE_UINT32));
+  EXPECT_TRUE(nullptr == GetMessageDescriptorForFieldType(FD::TYPE_ENUM));
+  EXPECT_TRUE(nullptr == GetMessageDescriptorForFieldType(FD::TYPE_SFIXED32));
+  EXPECT_TRUE(nullptr == GetMessageDescriptorForFieldType(FD::TYPE_SFIXED64));
+  EXPECT_TRUE(nullptr == GetMessageDescriptorForFieldType(FD::TYPE_SINT32));
+  EXPECT_TRUE(nullptr == GetMessageDescriptorForFieldType(FD::TYPE_SINT64));
+}
+
+TEST_F(MiscTest, EnumType) {
+  // Test that enum_type() is nullptr for non-enum fields
+
+  typedef FieldDescriptor FD;  // avoid ugly line wrapping
+
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_DOUBLE));
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_FLOAT));
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_INT64));
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_UINT64));
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_INT32));
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_FIXED64));
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_FIXED32));
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_BOOL));
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_STRING));
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_GROUP));
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_MESSAGE));
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_BYTES));
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_UINT32));
+  EXPECT_TRUE(nullptr != GetEnumDescriptorForFieldType(FD::TYPE_ENUM));
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_SFIXED32));
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_SFIXED64));
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_SINT32));
+  EXPECT_TRUE(nullptr == GetEnumDescriptorForFieldType(FD::TYPE_SINT64));
+}
+
+TEST_F(MiscTest, DefaultValues) {
+  // Test that setting default values works.
+  FileDescriptorProto file_proto;
+  file_proto.set_name("foo.proto");
+
+  EnumDescriptorProto* enum_type_proto = AddEnum(&file_proto, "DummyEnum");
+  AddEnumValue(enum_type_proto, "A", 1);
+  AddEnumValue(enum_type_proto, "B", 2);
+
+  DescriptorProto* message_proto = AddMessage(&file_proto, "TestMessage");
+
+  typedef FieldDescriptorProto FD;  // avoid ugly line wrapping
+  const FD::Label label = FD::LABEL_OPTIONAL;
+
+  // Create fields of every CPP type with default values.
+  AddField(message_proto, "int32", 1, label, FD::TYPE_INT32)
+      ->set_default_value("-1");
+  AddField(message_proto, "int64", 2, label, FD::TYPE_INT64)
+      ->set_default_value("-1000000000000");
+  AddField(message_proto, "uint32", 3, label, FD::TYPE_UINT32)
+      ->set_default_value("42");
+  AddField(message_proto, "uint64", 4, label, FD::TYPE_UINT64)
+      ->set_default_value("2000000000000");
+  AddField(message_proto, "float", 5, label, FD::TYPE_FLOAT)
+      ->set_default_value("4.5");
+  AddField(message_proto, "double", 6, label, FD::TYPE_DOUBLE)
+      ->set_default_value("10e100");
+  AddField(message_proto, "bool", 7, label, FD::TYPE_BOOL)
+      ->set_default_value("true");
+  AddField(message_proto, "string", 8, label, FD::TYPE_STRING)
+      ->set_default_value("hello");
+  AddField(message_proto, "data", 9, label, FD::TYPE_BYTES)
+      ->set_default_value("\\001\\002\\003");
+
+  FieldDescriptorProto* enum_field =
+      AddField(message_proto, "enum", 10, label, FD::TYPE_ENUM);
+  enum_field->set_type_name("DummyEnum");
+  enum_field->set_default_value("B");
+
+  // Strings are allowed to have empty defaults.  (At one point, due to
+  // a bug, empty defaults for strings were rejected.  Oops.)
+  AddField(message_proto, "empty_string", 11, label, FD::TYPE_STRING)
+      ->set_default_value("");
+
+  // Add a second set of fields with implicit default values.
+  AddField(message_proto, "implicit_int32", 21, label, FD::TYPE_INT32);
+  AddField(message_proto, "implicit_int64", 22, label, FD::TYPE_INT64);
+  AddField(message_proto, "implicit_uint32", 23, label, FD::TYPE_UINT32);
+  AddField(message_proto, "implicit_uint64", 24, label, FD::TYPE_UINT64);
+  AddField(message_proto, "implicit_float", 25, label, FD::TYPE_FLOAT);
+  AddField(message_proto, "implicit_double", 26, label, FD::TYPE_DOUBLE);
+  AddField(message_proto, "implicit_bool", 27, label, FD::TYPE_BOOL);
+  AddField(message_proto, "implicit_string", 28, label, FD::TYPE_STRING);
+  AddField(message_proto, "implicit_data", 29, label, FD::TYPE_BYTES);
+  AddField(message_proto, "implicit_enum", 30, label, FD::TYPE_ENUM)
+      ->set_type_name("DummyEnum");
+
+  // Build it.
+  DescriptorPool pool;
+  const FileDescriptor* file = pool.BuildFile(file_proto);
+  ASSERT_TRUE(file != nullptr);
+
+  ASSERT_EQ(1, file->enum_type_count());
+  const EnumDescriptor* enum_type = file->enum_type(0);
+  ASSERT_EQ(2, enum_type->value_count());
+  const EnumValueDescriptor* enum_value_a = enum_type->value(0);
+  const EnumValueDescriptor* enum_value_b = enum_type->value(1);
+
+  ASSERT_EQ(1, file->message_type_count());
+  const Descriptor* message = file->message_type(0);
+
+  ASSERT_EQ(21, message->field_count());
+
+  // Check the default values.
+  ASSERT_TRUE(message->field(0)->has_default_value());
+  ASSERT_TRUE(message->field(1)->has_default_value());
+  ASSERT_TRUE(message->field(2)->has_default_value());
+  ASSERT_TRUE(message->field(3)->has_default_value());
+  ASSERT_TRUE(message->field(4)->has_default_value());
+  ASSERT_TRUE(message->field(5)->has_default_value());
+  ASSERT_TRUE(message->field(6)->has_default_value());
+  ASSERT_TRUE(message->field(7)->has_default_value());
+  ASSERT_TRUE(message->field(8)->has_default_value());
+  ASSERT_TRUE(message->field(9)->has_default_value());
+  ASSERT_TRUE(message->field(10)->has_default_value());
+
+  EXPECT_EQ(-1, message->field(0)->default_value_int32());
+  EXPECT_EQ(int64{-1000000000000}, message->field(1)->default_value_int64());
+  EXPECT_EQ(42, message->field(2)->default_value_uint32());
+  EXPECT_EQ(uint64{2000000000000}, message->field(3)->default_value_uint64());
+  EXPECT_EQ(4.5, message->field(4)->default_value_float());
+  EXPECT_EQ(10e100, message->field(5)->default_value_double());
+  EXPECT_TRUE(message->field(6)->default_value_bool());
+  EXPECT_EQ("hello", message->field(7)->default_value_string());
+  EXPECT_EQ("\001\002\003", message->field(8)->default_value_string());
+  EXPECT_EQ(enum_value_b, message->field(9)->default_value_enum());
+  EXPECT_EQ("", message->field(10)->default_value_string());
+
+  ASSERT_FALSE(message->field(11)->has_default_value());
+  ASSERT_FALSE(message->field(12)->has_default_value());
+  ASSERT_FALSE(message->field(13)->has_default_value());
+  ASSERT_FALSE(message->field(14)->has_default_value());
+  ASSERT_FALSE(message->field(15)->has_default_value());
+  ASSERT_FALSE(message->field(16)->has_default_value());
+  ASSERT_FALSE(message->field(17)->has_default_value());
+  ASSERT_FALSE(message->field(18)->has_default_value());
+  ASSERT_FALSE(message->field(19)->has_default_value());
+  ASSERT_FALSE(message->field(20)->has_default_value());
+
+  EXPECT_EQ(0, message->field(11)->default_value_int32());
+  EXPECT_EQ(0, message->field(12)->default_value_int64());
+  EXPECT_EQ(0, message->field(13)->default_value_uint32());
+  EXPECT_EQ(0, message->field(14)->default_value_uint64());
+  EXPECT_EQ(0.0f, message->field(15)->default_value_float());
+  EXPECT_EQ(0.0, message->field(16)->default_value_double());
+  EXPECT_FALSE(message->field(17)->default_value_bool());
+  EXPECT_EQ("", message->field(18)->default_value_string());
+  EXPECT_EQ("", message->field(19)->default_value_string());
+  EXPECT_EQ(enum_value_a, message->field(20)->default_value_enum());
+}
+
+TEST_F(MiscTest, FieldOptions) {
+  // Try setting field options.
+
+  FileDescriptorProto file_proto;
+  file_proto.set_name("foo.proto");
+
+  DescriptorProto* message_proto = AddMessage(&file_proto, "TestMessage");
+  AddField(message_proto, "foo", 1, FieldDescriptorProto::LABEL_OPTIONAL,
+           FieldDescriptorProto::TYPE_INT32);
+  FieldDescriptorProto* bar_proto =
+      AddField(message_proto, "bar", 2, FieldDescriptorProto::LABEL_OPTIONAL,
+               FieldDescriptorProto::TYPE_INT32);
+
+  FieldOptions* options = bar_proto->mutable_options();
+  options->set_ctype(FieldOptions::CORD);
+
+  // Build the descriptors and get the pointers.
+  DescriptorPool pool;
+  const FileDescriptor* file = pool.BuildFile(file_proto);
+  ASSERT_TRUE(file != nullptr);
+
+  ASSERT_EQ(1, file->message_type_count());
+  const Descriptor* message = file->message_type(0);
+
+  ASSERT_EQ(2, message->field_count());
+  const FieldDescriptor* foo = message->field(0);
+  const FieldDescriptor* bar = message->field(1);
+
+  // "foo" had no options set, so it should return the default options.
+  EXPECT_EQ(&FieldOptions::default_instance(), &foo->options());
+
+  // "bar" had options set.
+  EXPECT_NE(&FieldOptions::default_instance(), options);
+  EXPECT_TRUE(bar->options().has_ctype());
+  EXPECT_EQ(FieldOptions::CORD, bar->options().ctype());
+}
+
+// ===================================================================
+enum DescriptorPoolMode { NO_DATABASE, FALLBACK_DATABASE };
+
+class AllowUnknownDependenciesTest
+    : public testing::TestWithParam<
+          std::tuple<DescriptorPoolMode, const char*>> {
+ protected:
+  DescriptorPoolMode mode() { return std::get<0>(GetParam()); }
+  const char* syntax() { return std::get<1>(GetParam()); }
+
+  void SetUp() override {
+    FileDescriptorProto foo_proto, bar_proto;
+
+    switch (mode()) {
+      case NO_DATABASE:
+        pool_.reset(new DescriptorPool);
+        break;
+      case FALLBACK_DATABASE:
+        pool_.reset(new DescriptorPool(&db_));
+        break;
+    }
+
+    pool_->AllowUnknownDependencies();
+
+    ASSERT_TRUE(TextFormat::ParseFromString(
+        "name: 'foo.proto'"
+        "dependency: 'bar.proto'"
+        "dependency: 'baz.proto'"
+        "message_type {"
+        "  name: 'Foo'"
+        "  field { name:'bar' number:1 label:LABEL_OPTIONAL type_name:'Bar' }"
+        "  field { name:'baz' number:2 label:LABEL_OPTIONAL type_name:'Baz' }"
+        "  field { name:'qux' number:3 label:LABEL_OPTIONAL"
+        "    type_name: '.corge.Qux'"
+        "    type: TYPE_ENUM"
+        "    options {"
+        "      uninterpreted_option {"
+        "        name {"
+        "          name_part: 'grault'"
+        "          is_extension: true"
+        "        }"
+        "        positive_int_value: 1234"
+        "      }"
+        "    }"
+        "  }"
+        "}",
+        &foo_proto));
+    foo_proto.set_syntax(syntax());
+
+    ASSERT_TRUE(
+        TextFormat::ParseFromString("name: 'bar.proto'"
+                                    "message_type { name: 'Bar' }",
+                                    &bar_proto));
+    bar_proto.set_syntax(syntax());
+
+    // Collect pointers to stuff.
+    bar_file_ = BuildFile(bar_proto);
+    ASSERT_TRUE(bar_file_ != nullptr);
+
+    ASSERT_EQ(1, bar_file_->message_type_count());
+    bar_type_ = bar_file_->message_type(0);
+
+    foo_file_ = BuildFile(foo_proto);
+    ASSERT_TRUE(foo_file_ != nullptr);
+
+    ASSERT_EQ(1, foo_file_->message_type_count());
+    foo_type_ = foo_file_->message_type(0);
+
+    ASSERT_EQ(3, foo_type_->field_count());
+    bar_field_ = foo_type_->field(0);
+    baz_field_ = foo_type_->field(1);
+    qux_field_ = foo_type_->field(2);
+  }
+
+  const FileDescriptor* BuildFile(const FileDescriptorProto& proto) {
+    switch (mode()) {
+      case NO_DATABASE:
+        return pool_->BuildFile(proto);
+        break;
+      case FALLBACK_DATABASE: {
+        EXPECT_TRUE(db_.Add(proto));
+        return pool_->FindFileByName(proto.name());
+      }
+    }
+    GOOGLE_LOG(FATAL) << "Can't get here.";
+    return nullptr;
+  }
+
+  const FileDescriptor* bar_file_;
+  const Descriptor* bar_type_;
+  const FileDescriptor* foo_file_;
+  const Descriptor* foo_type_;
+  const FieldDescriptor* bar_field_;
+  const FieldDescriptor* baz_field_;
+  const FieldDescriptor* qux_field_;
+
+  SimpleDescriptorDatabase db_;  // used if in FALLBACK_DATABASE mode.
+  std::unique_ptr<DescriptorPool> pool_;
+};
+
+TEST_P(AllowUnknownDependenciesTest, PlaceholderFile) {
+  ASSERT_EQ(2, foo_file_->dependency_count());
+  EXPECT_EQ(bar_file_, foo_file_->dependency(0));
+  EXPECT_FALSE(bar_file_->is_placeholder());
+
+  const FileDescriptor* baz_file = foo_file_->dependency(1);
+  EXPECT_EQ("baz.proto", baz_file->name());
+  EXPECT_EQ(0, baz_file->message_type_count());
+  EXPECT_TRUE(baz_file->is_placeholder());
+
+  // Placeholder files should not be findable.
+  EXPECT_EQ(bar_file_, pool_->FindFileByName(bar_file_->name()));
+  EXPECT_TRUE(pool_->FindFileByName(baz_file->name()) == nullptr);
+
+  // Copy*To should not crash for placeholder files.
+  FileDescriptorProto baz_file_proto;
+  baz_file->CopyTo(&baz_file_proto);
+  baz_file->CopySourceCodeInfoTo(&baz_file_proto);
+  EXPECT_FALSE(baz_file_proto.has_source_code_info());
+}
+
+TEST_P(AllowUnknownDependenciesTest, PlaceholderTypes) {
+  ASSERT_EQ(FieldDescriptor::TYPE_MESSAGE, bar_field_->type());
+  EXPECT_EQ(bar_type_, bar_field_->message_type());
+  EXPECT_FALSE(bar_type_->is_placeholder());
+
+  ASSERT_EQ(FieldDescriptor::TYPE_MESSAGE, baz_field_->type());
+  const Descriptor* baz_type = baz_field_->message_type();
+  EXPECT_EQ("Baz", baz_type->name());
+  EXPECT_EQ("Baz", baz_type->full_name());
+  EXPECT_EQ(0, baz_type->extension_range_count());
+  EXPECT_TRUE(baz_type->is_placeholder());
+
+  ASSERT_EQ(FieldDescriptor::TYPE_ENUM, qux_field_->type());
+  const EnumDescriptor* qux_type = qux_field_->enum_type();
+  EXPECT_EQ("Qux", qux_type->name());
+  EXPECT_EQ("corge.Qux", qux_type->full_name());
+  EXPECT_TRUE(qux_type->is_placeholder());
+  // Placeholder enum values should not be findable.
+  EXPECT_EQ(qux_type->FindValueByNumber(0), nullptr);
+
+  // Placeholder types should not be findable.
+  EXPECT_EQ(bar_type_, pool_->FindMessageTypeByName(bar_type_->full_name()));
+  EXPECT_TRUE(pool_->FindMessageTypeByName(baz_type->full_name()) == nullptr);
+  EXPECT_TRUE(pool_->FindEnumTypeByName(qux_type->full_name()) == nullptr);
+}
+
+TEST_P(AllowUnknownDependenciesTest, CopyTo) {
+  // FieldDescriptor::CopyTo() should write non-fully-qualified type names
+  // for placeholder types which were not originally fully-qualified.
+  FieldDescriptorProto proto;
+
+  // Bar is not a placeholder, so it is fully-qualified.
+  bar_field_->CopyTo(&proto);
+  EXPECT_EQ(".Bar", proto.type_name());
+  EXPECT_EQ(FieldDescriptorProto::TYPE_MESSAGE, proto.type());
+
+  // Baz is an unqualified placeholder.
+  proto.Clear();
+  baz_field_->CopyTo(&proto);
+  EXPECT_EQ("Baz", proto.type_name());
+  EXPECT_FALSE(proto.has_type());
+
+  // Qux is a fully-qualified placeholder.
+  proto.Clear();
+  qux_field_->CopyTo(&proto);
+  EXPECT_EQ(".corge.Qux", proto.type_name());
+  EXPECT_EQ(FieldDescriptorProto::TYPE_ENUM, proto.type());
+}
+
+TEST_P(AllowUnknownDependenciesTest, CustomOptions) {
+  // Qux should still have the uninterpreted option attached.
+  ASSERT_EQ(1, qux_field_->options().uninterpreted_option_size());
+  const UninterpretedOption& option =
+      qux_field_->options().uninterpreted_option(0);
+  ASSERT_EQ(1, option.name_size());
+  EXPECT_EQ("grault", option.name(0).name_part());
+}
+
+TEST_P(AllowUnknownDependenciesTest, UnknownExtendee) {
+  // Test that we can extend an unknown type.  This is slightly tricky because
+  // it means that the placeholder type must have an extension range.
+
+  FileDescriptorProto extension_proto;
+
+  ASSERT_TRUE(TextFormat::ParseFromString(
+      "name: 'extension.proto'"
+      "extension { extendee: 'UnknownType' name:'some_extension' number:123"
+      "            label:LABEL_OPTIONAL type:TYPE_INT32 }",
+      &extension_proto));
+  const FileDescriptor* file = BuildFile(extension_proto);
+
+  ASSERT_TRUE(file != nullptr);
+
+  ASSERT_EQ(1, file->extension_count());
+  const Descriptor* extendee = file->extension(0)->containing_type();
+  EXPECT_EQ("UnknownType", extendee->name());
+  EXPECT_TRUE(extendee->is_placeholder());
+  ASSERT_EQ(1, extendee->extension_range_count());
+  EXPECT_EQ(1, extendee->extension_range(0)->start);
+  EXPECT_EQ(FieldDescriptor::kMaxNumber + 1, extendee->extension_range(0)->end);
+}
+
+TEST_P(AllowUnknownDependenciesTest, CustomOption) {
+  // Test that we can use a custom option without having parsed
+  // descriptor.proto.
+
+  FileDescriptorProto option_proto;
+
+  ASSERT_TRUE(TextFormat::ParseFromString(
+      "name: \"unknown_custom_options.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "extension { "
+      "  extendee: \"google.protobuf.FileOptions\" "
+      "  name: \"some_option\" "
+      "  number: 123456 "
+      "  label: LABEL_OPTIONAL "
+      "  type: TYPE_INT32 "
+      "} "
+      "options { "
+      "  uninterpreted_option { "
+      "    name { "
+      "      name_part: \"some_option\" "
+      "      is_extension: true "
+      "    } "
+      "    positive_int_value: 1234 "
+      "  } "
+      "  uninterpreted_option { "
+      "    name { "
+      "      name_part: \"unknown_option\" "
+      "      is_extension: true "
+      "    } "
+      "    positive_int_value: 1234 "
+      "  } "
+      "  uninterpreted_option { "
+      "    name { "
+      "      name_part: \"optimize_for\" "
+      "      is_extension: false "
+      "    } "
+      "    identifier_value: \"SPEED\" "
+      "  } "
+      "}",
+      &option_proto));
+
+  const FileDescriptor* file = BuildFile(option_proto);
+  ASSERT_TRUE(file != nullptr);
+
+  // Verify that no extension options were set, but they were left as
+  // uninterpreted_options.
+  std::vector<const FieldDescriptor*> fields;
+  file->options().GetReflection()->ListFields(file->options(), &fields);
+  ASSERT_EQ(2, fields.size());
+  EXPECT_TRUE(file->options().has_optimize_for());
+  EXPECT_EQ(2, file->options().uninterpreted_option_size());
+}
+
+TEST_P(AllowUnknownDependenciesTest,
+       UndeclaredDependencyTriggersBuildOfDependency) {
+  // Crazy case: suppose foo.proto refers to a symbol without declaring the
+  // dependency that finds it. In the event that the pool is backed by a
+  // DescriptorDatabase, the pool will attempt to find the symbol in the
+  // database. If successful, it will build the undeclared dependency to verify
+  // that the file does indeed contain the symbol. If that file fails to build,
+  // then its descriptors must be rolled back. However, we still want foo.proto
+  // to build successfully, since we are allowing unknown dependencies.
+
+  FileDescriptorProto undeclared_dep_proto;
+  // We make this file fail to build by giving it two fields with tag 1.
+  ASSERT_TRUE(TextFormat::ParseFromString(
+      "name: \"invalid_file_as_undeclared_dep.proto\" "
+      "package: \"undeclared\" "
+      "message_type: {  "
+      "  name: \"Quux\"  "
+      "  field { "
+      "    name:'qux' number:1 label:LABEL_OPTIONAL type: TYPE_INT32 "
+      "  }"
+      "  field { "
+      "    name:'quux' number:1 label:LABEL_OPTIONAL type: TYPE_INT64 "
+      "  }"
+      "}",
+      &undeclared_dep_proto));
+  // We can't use the BuildFile() helper because we don't actually want to build
+  // it into the descriptor pool in the fallback database case: it just needs to
+  // be sitting in the database so that it gets built during the building of
+  // test.proto below.
+  switch (mode()) {
+    case NO_DATABASE: {
+      ASSERT_TRUE(pool_->BuildFile(undeclared_dep_proto) == nullptr);
+      break;
+    }
+    case FALLBACK_DATABASE: {
+      ASSERT_TRUE(db_.Add(undeclared_dep_proto));
+    }
+  }
+
+  FileDescriptorProto test_proto;
+  ASSERT_TRUE(TextFormat::ParseFromString(
+      "name: \"test.proto\" "
+      "message_type: { "
+      "  name: \"Corge\" "
+      "  field { "
+      "    name:'quux' number:1 label: LABEL_OPTIONAL "
+      "    type_name:'undeclared.Quux' type: TYPE_MESSAGE "
+      "  }"
+      "}",
+      &test_proto));
+
+  const FileDescriptor* file = BuildFile(test_proto);
+  ASSERT_TRUE(file != nullptr);
+  GOOGLE_LOG(INFO) << file->DebugString();
+
+  EXPECT_EQ(0, file->dependency_count());
+  ASSERT_EQ(1, file->message_type_count());
+  const Descriptor* corge_desc = file->message_type(0);
+  ASSERT_EQ("Corge", corge_desc->name());
+  ASSERT_EQ(1, corge_desc->field_count());
+  EXPECT_FALSE(corge_desc->is_placeholder());
+
+  const FieldDescriptor* quux_field = corge_desc->field(0);
+  ASSERT_EQ(FieldDescriptor::TYPE_MESSAGE, quux_field->type());
+  ASSERT_EQ("Quux", quux_field->message_type()->name());
+  ASSERT_EQ("undeclared.Quux", quux_field->message_type()->full_name());
+  EXPECT_TRUE(quux_field->message_type()->is_placeholder());
+  // The place holder type should not be findable.
+  ASSERT_TRUE(pool_->FindMessageTypeByName("undeclared.Quux") == nullptr);
+}
+
+INSTANTIATE_TEST_SUITE_P(DatabaseSource, AllowUnknownDependenciesTest,
+                         testing::Combine(testing::Values(NO_DATABASE,
+                                                          FALLBACK_DATABASE),
+                                          testing::Values("proto2", "proto3")));
+
+// ===================================================================
+
+TEST(CustomOptions, OptionLocations) {
+  const Descriptor* message =
+      protobuf_unittest::TestMessageWithCustomOptions::descriptor();
+  const FileDescriptor* file = message->file();
+  const FieldDescriptor* field = message->FindFieldByName("field1");
+  const OneofDescriptor* oneof = message->FindOneofByName("AnOneof");
+  const FieldDescriptor* map_field = message->FindFieldByName("map_field");
+  const EnumDescriptor* enm = message->FindEnumTypeByName("AnEnum");
+  // TODO(benjy): Support EnumValue options, once the compiler does.
+  const ServiceDescriptor* service =
+      file->FindServiceByName("TestServiceWithCustomOptions");
+  const MethodDescriptor* method = service->FindMethodByName("Foo");
+
+  EXPECT_EQ(int64{9876543210},
+            file->options().GetExtension(protobuf_unittest::file_opt1));
+  EXPECT_EQ(-56,
+            message->options().GetExtension(protobuf_unittest::message_opt1));
+  EXPECT_EQ(int64{8765432109},
+            field->options().GetExtension(protobuf_unittest::field_opt1));
+  EXPECT_EQ(42,  // Check that we get the default for an option we don't set.
+            field->options().GetExtension(protobuf_unittest::field_opt2));
+  EXPECT_EQ(-99, oneof->options().GetExtension(protobuf_unittest::oneof_opt1));
+  EXPECT_EQ(int64_t{12345},
+            map_field->options().GetExtension(protobuf_unittest::field_opt1));
+  EXPECT_EQ(-789, enm->options().GetExtension(protobuf_unittest::enum_opt1));
+  EXPECT_EQ(123, enm->value(1)->options().GetExtension(
+                     protobuf_unittest::enum_value_opt1));
+  EXPECT_EQ(int64{-9876543210},
+            service->options().GetExtension(protobuf_unittest::service_opt1));
+  EXPECT_EQ(protobuf_unittest::METHODOPT1_VAL2,
+            method->options().GetExtension(protobuf_unittest::method_opt1));
+
+  // See that the regular options went through unscathed.
+  EXPECT_TRUE(message->options().has_message_set_wire_format());
+  EXPECT_EQ(FieldOptions::CORD, field->options().ctype());
+}
+
+TEST(CustomOptions, OptionTypes) {
+  const MessageOptions* options = nullptr;
+
+  constexpr int32_t kint32min = std::numeric_limits<int32_t>::min();
+  constexpr int32_t kint32max = std::numeric_limits<int32_t>::max();
+  constexpr uint32_t kuint32max = std::numeric_limits<uint32_t>::max();
+  constexpr int64_t kint64min = std::numeric_limits<int64_t>::min();
+  constexpr int64_t kint64max = std::numeric_limits<int64_t>::max();
+  constexpr uint64_t kuint64max = std::numeric_limits<uint64_t>::max();
+
+  options =
+      &protobuf_unittest::CustomOptionMinIntegerValues::descriptor()->options();
+  EXPECT_EQ(false, options->GetExtension(protobuf_unittest::bool_opt));
+  EXPECT_EQ(kint32min, options->GetExtension(protobuf_unittest::int32_opt));
+  EXPECT_EQ(kint64min, options->GetExtension(protobuf_unittest::int64_opt));
+  EXPECT_EQ(0, options->GetExtension(protobuf_unittest::uint32_opt));
+  EXPECT_EQ(0, options->GetExtension(protobuf_unittest::uint64_opt));
+  EXPECT_EQ(kint32min, options->GetExtension(protobuf_unittest::sint32_opt));
+  EXPECT_EQ(kint64min, options->GetExtension(protobuf_unittest::sint64_opt));
+  EXPECT_EQ(0, options->GetExtension(protobuf_unittest::fixed32_opt));
+  EXPECT_EQ(0, options->GetExtension(protobuf_unittest::fixed64_opt));
+  EXPECT_EQ(kint32min, options->GetExtension(protobuf_unittest::sfixed32_opt));
+  EXPECT_EQ(kint64min, options->GetExtension(protobuf_unittest::sfixed64_opt));
+
+  options =
+      &protobuf_unittest::CustomOptionMaxIntegerValues::descriptor()->options();
+  EXPECT_EQ(true, options->GetExtension(protobuf_unittest::bool_opt));
+  EXPECT_EQ(kint32max, options->GetExtension(protobuf_unittest::int32_opt));
+  EXPECT_EQ(kint64max, options->GetExtension(protobuf_unittest::int64_opt));
+  EXPECT_EQ(kuint32max, options->GetExtension(protobuf_unittest::uint32_opt));
+  EXPECT_EQ(kuint64max, options->GetExtension(protobuf_unittest::uint64_opt));
+  EXPECT_EQ(kint32max, options->GetExtension(protobuf_unittest::sint32_opt));
+  EXPECT_EQ(kint64max, options->GetExtension(protobuf_unittest::sint64_opt));
+  EXPECT_EQ(kuint32max, options->GetExtension(protobuf_unittest::fixed32_opt));
+  EXPECT_EQ(kuint64max, options->GetExtension(protobuf_unittest::fixed64_opt));
+  EXPECT_EQ(kint32max, options->GetExtension(protobuf_unittest::sfixed32_opt));
+  EXPECT_EQ(kint64max, options->GetExtension(protobuf_unittest::sfixed64_opt));
+
+  options = &protobuf_unittest::CustomOptionOtherValues::descriptor()->options();
+  EXPECT_EQ(-100, options->GetExtension(protobuf_unittest::int32_opt));
+  EXPECT_FLOAT_EQ(12.3456789,
+                  options->GetExtension(protobuf_unittest::float_opt));
+  EXPECT_DOUBLE_EQ(1.234567890123456789,
+                   options->GetExtension(protobuf_unittest::double_opt));
+  EXPECT_EQ("Hello, \"World\"",
+            options->GetExtension(protobuf_unittest::string_opt));
+
+  EXPECT_EQ(std::string("Hello\0World", 11),
+            options->GetExtension(protobuf_unittest::bytes_opt));
+
+  EXPECT_EQ(protobuf_unittest::DummyMessageContainingEnum::TEST_OPTION_ENUM_TYPE2,
+            options->GetExtension(protobuf_unittest::enum_opt));
+
+  options =
+      &protobuf_unittest::SettingRealsFromPositiveInts::descriptor()->options();
+  EXPECT_FLOAT_EQ(12, options->GetExtension(protobuf_unittest::float_opt));
+  EXPECT_DOUBLE_EQ(154, options->GetExtension(protobuf_unittest::double_opt));
+
+  options =
+      &protobuf_unittest::SettingRealsFromNegativeInts::descriptor()->options();
+  EXPECT_FLOAT_EQ(-12, options->GetExtension(protobuf_unittest::float_opt));
+  EXPECT_DOUBLE_EQ(-154, options->GetExtension(protobuf_unittest::double_opt));
+}
+
+TEST(CustomOptions, ComplexExtensionOptions) {
+  const MessageOptions* options =
+      &protobuf_unittest::VariousComplexOptions::descriptor()->options();
+  EXPECT_EQ(options->GetExtension(protobuf_unittest::complex_opt1).foo(), 42);
+  EXPECT_EQ(options->GetExtension(protobuf_unittest::complex_opt1)
+                .GetExtension(protobuf_unittest::quux),
+            324);
+  EXPECT_EQ(options->GetExtension(protobuf_unittest::complex_opt1)
+                .GetExtension(protobuf_unittest::corge)
+                .qux(),
+            876);
+  EXPECT_EQ(options->GetExtension(protobuf_unittest::complex_opt2).baz(), 987);
+  EXPECT_EQ(options->GetExtension(protobuf_unittest::complex_opt2)
+                .GetExtension(protobuf_unittest::grault),
+            654);
+  EXPECT_EQ(options->GetExtension(protobuf_unittest::complex_opt2).bar().foo(),
+            743);
+  EXPECT_EQ(options->GetExtension(protobuf_unittest::complex_opt2)
+                .bar()
+                .GetExtension(protobuf_unittest::quux),
+            1999);
+  EXPECT_EQ(options->GetExtension(protobuf_unittest::complex_opt2)
+                .bar()
+                .GetExtension(protobuf_unittest::corge)
+                .qux(),
+            2008);
+  EXPECT_EQ(options->GetExtension(protobuf_unittest::complex_opt2)
+                .GetExtension(protobuf_unittest::garply)
+                .foo(),
+            741);
+  EXPECT_EQ(options->GetExtension(protobuf_unittest::complex_opt2)
+                .GetExtension(protobuf_unittest::garply)
+                .GetExtension(protobuf_unittest::quux),
+            1998);
+  EXPECT_EQ(options->GetExtension(protobuf_unittest::complex_opt2)
+                .GetExtension(protobuf_unittest::garply)
+                .GetExtension(protobuf_unittest::corge)
+                .qux(),
+            2121);
+  EXPECT_EQ(options
+                ->GetExtension(protobuf_unittest::ComplexOptionType2::
+                                   ComplexOptionType4::complex_opt4)
+                .waldo(),
+            1971);
+  EXPECT_EQ(options->GetExtension(protobuf_unittest::complex_opt2).fred().waldo(),
+            321);
+  EXPECT_EQ(9, options->GetExtension(protobuf_unittest::complex_opt3).qux());
+  EXPECT_EQ(22, options->GetExtension(protobuf_unittest::complex_opt3)
+                    .complexoptiontype5()
+                    .plugh());
+  EXPECT_EQ(24, options->GetExtension(protobuf_unittest::complexopt6).xyzzy());
+}
+
+TEST(CustomOptions, OptionsFromOtherFile) {
+  // Test that to use a custom option, we only need to import the file
+  // defining the option; we do not also have to import descriptor.proto.
+  DescriptorPool pool;
+
+  FileDescriptorProto file_proto;
+  FileDescriptorProto::descriptor()->file()->CopyTo(&file_proto);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+
+  // We have to import the Any dependency.
+  FileDescriptorProto any_proto;
+  google::protobuf::Any::descriptor()->file()->CopyTo(&any_proto);
+  ASSERT_TRUE(pool.BuildFile(any_proto) != nullptr);
+
+  protobuf_unittest::TestMessageWithCustomOptions::descriptor()->file()->CopyTo(
+      &file_proto);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+
+  ASSERT_TRUE(TextFormat::ParseFromString(
+      "name: \"custom_options_import.proto\" "
+      "package: \"protobuf_unittest\" "
+      "dependency: \"google/protobuf/unittest_custom_options.proto\" "
+      "options { "
+      "  uninterpreted_option { "
+      "    name { "
+      "      name_part: \"file_opt1\" "
+      "      is_extension: true "
+      "    } "
+      "    positive_int_value: 1234 "
+      "  } "
+      // Test a non-extension option too.  (At one point this failed due to a
+      // bug.)
+      "  uninterpreted_option { "
+      "    name { "
+      "      name_part: \"java_package\" "
+      "      is_extension: false "
+      "    } "
+      "    string_value: \"foo\" "
+      "  } "
+      // Test that enum-typed options still work too.  (At one point this also
+      // failed due to a bug.)
+      "  uninterpreted_option { "
+      "    name { "
+      "      name_part: \"optimize_for\" "
+      "      is_extension: false "
+      "    } "
+      "    identifier_value: \"SPEED\" "
+      "  } "
+      "}",
+      &file_proto));
+
+  const FileDescriptor* file = pool.BuildFile(file_proto);
+  ASSERT_TRUE(file != nullptr);
+  EXPECT_EQ(1234, file->options().GetExtension(protobuf_unittest::file_opt1));
+  EXPECT_TRUE(file->options().has_java_package());
+  EXPECT_EQ("foo", file->options().java_package());
+  EXPECT_TRUE(file->options().has_optimize_for());
+  EXPECT_EQ(FileOptions::SPEED, file->options().optimize_for());
+}
+
+TEST(CustomOptions, MessageOptionThreeFieldsSet) {
+  // This tests a bug which previously existed in custom options parsing.  The
+  // bug occurred when you defined a custom option with message type and then
+  // set three fields of that option on a single definition (see the example
+  // below).  The bug is a bit hard to explain, so check the change history if
+  // you want to know more.
+  DescriptorPool pool;
+
+  FileDescriptorProto file_proto;
+  FileDescriptorProto::descriptor()->file()->CopyTo(&file_proto);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+
+  FileDescriptorProto any_proto;
+  google::protobuf::Any::descriptor()->file()->CopyTo(&any_proto);
+  ASSERT_TRUE(pool.BuildFile(any_proto) != nullptr);
+
+  protobuf_unittest::TestMessageWithCustomOptions::descriptor()->file()->CopyTo(
+      &file_proto);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+
+  // The following represents the definition:
+  //
+  //   import "google/protobuf/unittest_custom_options.proto"
+  //   package protobuf_unittest;
+  //   message Foo {
+  //     option (complex_opt1).foo  = 1234;
+  //     option (complex_opt1).foo2 = 1234;
+  //     option (complex_opt1).foo3 = 1234;
+  //   }
+  ASSERT_TRUE(TextFormat::ParseFromString(
+      "name: \"custom_options_import.proto\" "
+      "package: \"protobuf_unittest\" "
+      "dependency: \"google/protobuf/unittest_custom_options.proto\" "
+      "message_type { "
+      "  name: \"Foo\" "
+      "  options { "
+      "    uninterpreted_option { "
+      "      name { "
+      "        name_part: \"complex_opt1\" "
+      "        is_extension: true "
+      "      } "
+      "      name { "
+      "        name_part: \"foo\" "
+      "        is_extension: false "
+      "      } "
+      "      positive_int_value: 1234 "
+      "    } "
+      "    uninterpreted_option { "
+      "      name { "
+      "        name_part: \"complex_opt1\" "
+      "        is_extension: true "
+      "      } "
+      "      name { "
+      "        name_part: \"foo2\" "
+      "        is_extension: false "
+      "      } "
+      "      positive_int_value: 1234 "
+      "    } "
+      "    uninterpreted_option { "
+      "      name { "
+      "        name_part: \"complex_opt1\" "
+      "        is_extension: true "
+      "      } "
+      "      name { "
+      "        name_part: \"foo3\" "
+      "        is_extension: false "
+      "      } "
+      "      positive_int_value: 1234 "
+      "    } "
+      "  } "
+      "}",
+      &file_proto));
+
+  const FileDescriptor* file = pool.BuildFile(file_proto);
+  ASSERT_TRUE(file != nullptr);
+  ASSERT_EQ(1, file->message_type_count());
+
+  const MessageOptions& options = file->message_type(0)->options();
+  EXPECT_EQ(1234, options.GetExtension(protobuf_unittest::complex_opt1).foo());
+}
+
+TEST(CustomOptions, MessageOptionRepeatedLeafFieldSet) {
+  // This test verifies that repeated fields in custom options can be
+  // given multiple values by repeating the option with a different value.
+  // This test checks repeated leaf values. Each repeated custom value
+  // appears in a different uninterpreted_option, which will be concatenated
+  // when they are merged into the final option value.
+  DescriptorPool pool;
+
+  FileDescriptorProto file_proto;
+  FileDescriptorProto::descriptor()->file()->CopyTo(&file_proto);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+
+  FileDescriptorProto any_proto;
+  google::protobuf::Any::descriptor()->file()->CopyTo(&any_proto);
+  ASSERT_TRUE(pool.BuildFile(any_proto) != nullptr);
+
+  protobuf_unittest::TestMessageWithCustomOptions::descriptor()->file()->CopyTo(
+      &file_proto);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+
+  // The following represents the definition:
+  //
+  //   import "google/protobuf/unittest_custom_options.proto"
+  //   package protobuf_unittest;
+  //   message Foo {
+  //     option (complex_opt1).foo4 = 12;
+  //     option (complex_opt1).foo4 = 34;
+  //     option (complex_opt1).foo4 = 56;
+  //   }
+  ASSERT_TRUE(TextFormat::ParseFromString(
+      "name: \"custom_options_import.proto\" "
+      "package: \"protobuf_unittest\" "
+      "dependency: \"google/protobuf/unittest_custom_options.proto\" "
+      "message_type { "
+      "  name: \"Foo\" "
+      "  options { "
+      "    uninterpreted_option { "
+      "      name { "
+      "        name_part: \"complex_opt1\" "
+      "        is_extension: true "
+      "      } "
+      "      name { "
+      "        name_part: \"foo4\" "
+      "        is_extension: false "
+      "      } "
+      "      positive_int_value: 12 "
+      "    } "
+      "    uninterpreted_option { "
+      "      name { "
+      "        name_part: \"complex_opt1\" "
+      "        is_extension: true "
+      "      } "
+      "      name { "
+      "        name_part: \"foo4\" "
+      "        is_extension: false "
+      "      } "
+      "      positive_int_value: 34 "
+      "    } "
+      "    uninterpreted_option { "
+      "      name { "
+      "        name_part: \"complex_opt1\" "
+      "        is_extension: true "
+      "      } "
+      "      name { "
+      "        name_part: \"foo4\" "
+      "        is_extension: false "
+      "      } "
+      "      positive_int_value: 56 "
+      "    } "
+      "  } "
+      "}",
+      &file_proto));
+
+  const FileDescriptor* file = pool.BuildFile(file_proto);
+  ASSERT_TRUE(file != nullptr);
+  ASSERT_EQ(1, file->message_type_count());
+
+  const MessageOptions& options = file->message_type(0)->options();
+  EXPECT_EQ(3, options.GetExtension(protobuf_unittest::complex_opt1).foo4_size());
+  EXPECT_EQ(12, options.GetExtension(protobuf_unittest::complex_opt1).foo4(0));
+  EXPECT_EQ(34, options.GetExtension(protobuf_unittest::complex_opt1).foo4(1));
+  EXPECT_EQ(56, options.GetExtension(protobuf_unittest::complex_opt1).foo4(2));
+}
+
+TEST(CustomOptions, MessageOptionRepeatedMsgFieldSet) {
+  // This test verifies that repeated fields in custom options can be
+  // given multiple values by repeating the option with a different value.
+  // This test checks repeated message values. Each repeated custom value
+  // appears in a different uninterpreted_option, which will be concatenated
+  // when they are merged into the final option value.
+  DescriptorPool pool;
+
+  FileDescriptorProto file_proto;
+  FileDescriptorProto::descriptor()->file()->CopyTo(&file_proto);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+
+  FileDescriptorProto any_proto;
+  google::protobuf::Any::descriptor()->file()->CopyTo(&any_proto);
+  ASSERT_TRUE(pool.BuildFile(any_proto) != nullptr);
+
+  protobuf_unittest::TestMessageWithCustomOptions::descriptor()->file()->CopyTo(
+      &file_proto);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+
+  // The following represents the definition:
+  //
+  //   import "google/protobuf/unittest_custom_options.proto"
+  //   package protobuf_unittest;
+  //   message Foo {
+  //     option (complex_opt2).barney = {waldo: 1};
+  //     option (complex_opt2).barney = {waldo: 10};
+  //     option (complex_opt2).barney = {waldo: 100};
+  //   }
+  ASSERT_TRUE(TextFormat::ParseFromString(
+      "name: \"custom_options_import.proto\" "
+      "package: \"protobuf_unittest\" "
+      "dependency: \"google/protobuf/unittest_custom_options.proto\" "
+      "message_type { "
+      "  name: \"Foo\" "
+      "  options { "
+      "    uninterpreted_option { "
+      "      name { "
+      "        name_part: \"complex_opt2\" "
+      "        is_extension: true "
+      "      } "
+      "      name { "
+      "        name_part: \"barney\" "
+      "        is_extension: false "
+      "      } "
+      "      aggregate_value: \"waldo: 1\" "
+      "    } "
+      "    uninterpreted_option { "
+      "      name { "
+      "        name_part: \"complex_opt2\" "
+      "        is_extension: true "
+      "      } "
+      "      name { "
+      "        name_part: \"barney\" "
+      "        is_extension: false "
+      "      } "
+      "      aggregate_value: \"waldo: 10\" "
+      "    } "
+      "    uninterpreted_option { "
+      "      name { "
+      "        name_part: \"complex_opt2\" "
+      "        is_extension: true "
+      "      } "
+      "      name { "
+      "        name_part: \"barney\" "
+      "        is_extension: false "
+      "      } "
+      "      aggregate_value: \"waldo: 100\" "
+      "    } "
+      "  } "
+      "}",
+      &file_proto));
+
+  const FileDescriptor* file = pool.BuildFile(file_proto);
+  ASSERT_TRUE(file != nullptr);
+  ASSERT_EQ(1, file->message_type_count());
+
+  const MessageOptions& options = file->message_type(0)->options();
+  EXPECT_EQ(3,
+            options.GetExtension(protobuf_unittest::complex_opt2).barney_size());
+  EXPECT_EQ(
+      1, options.GetExtension(protobuf_unittest::complex_opt2).barney(0).waldo());
+  EXPECT_EQ(
+      10,
+      options.GetExtension(protobuf_unittest::complex_opt2).barney(1).waldo());
+  EXPECT_EQ(
+      100,
+      options.GetExtension(protobuf_unittest::complex_opt2).barney(2).waldo());
+}
+
+// Check that aggregate options were parsed and saved correctly in
+// the appropriate descriptors.
+TEST(CustomOptions, AggregateOptions) {
+  const Descriptor* msg = protobuf_unittest::AggregateMessage::descriptor();
+  const FileDescriptor* file = msg->file();
+  const FieldDescriptor* field = msg->FindFieldByName("fieldname");
+  const EnumDescriptor* enumd = file->FindEnumTypeByName("AggregateEnum");
+  const EnumValueDescriptor* enumv = enumd->FindValueByName("VALUE");
+  const ServiceDescriptor* service =
+      file->FindServiceByName("AggregateService");
+  const MethodDescriptor* method = service->FindMethodByName("Method");
+
+  // Tests for the different types of data embedded in fileopt
+  const protobuf_unittest::Aggregate& file_options =
+      file->options().GetExtension(protobuf_unittest::fileopt);
+  EXPECT_EQ(100, file_options.i());
+  EXPECT_EQ("FileAnnotation", file_options.s());
+  EXPECT_EQ("NestedFileAnnotation", file_options.sub().s());
+  EXPECT_EQ("FileExtensionAnnotation",
+            file_options.file().GetExtension(protobuf_unittest::fileopt).s());
+  EXPECT_EQ("EmbeddedMessageSetElement",
+            file_options.mset()
+                .GetExtension(protobuf_unittest::AggregateMessageSetElement ::
+                                  message_set_extension)
+                .s());
+
+  protobuf_unittest::AggregateMessageSetElement any_payload;
+  ASSERT_TRUE(file_options.any().UnpackTo(&any_payload));
+  EXPECT_EQ("EmbeddedMessageSetElement", any_payload.s());
+
+  // Simple tests for all the other types of annotations
+  EXPECT_EQ("MessageAnnotation",
+            msg->options().GetExtension(protobuf_unittest::msgopt).s());
+  EXPECT_EQ("FieldAnnotation",
+            field->options().GetExtension(protobuf_unittest::fieldopt).s());
+  EXPECT_EQ("EnumAnnotation",
+            enumd->options().GetExtension(protobuf_unittest::enumopt).s());
+  EXPECT_EQ("EnumValueAnnotation",
+            enumv->options().GetExtension(protobuf_unittest::enumvalopt).s());
+  EXPECT_EQ("ServiceAnnotation",
+            service->options().GetExtension(protobuf_unittest::serviceopt).s());
+  EXPECT_EQ("MethodAnnotation",
+            method->options().GetExtension(protobuf_unittest::methodopt).s());
+}
+
+TEST(CustomOptions, UnusedImportError) {
+  DescriptorPool pool;
+
+  FileDescriptorProto file_proto;
+  FileDescriptorProto::descriptor()->file()->CopyTo(&file_proto);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+
+  FileDescriptorProto any_proto;
+  google::protobuf::Any::descriptor()->file()->CopyTo(&any_proto);
+  ASSERT_TRUE(pool.BuildFile(any_proto) != nullptr);
+
+  protobuf_unittest::TestMessageWithCustomOptions::descriptor()->file()->CopyTo(
+      &file_proto);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+
+  pool.AddUnusedImportTrackFile("custom_options_import.proto", true);
+  ASSERT_TRUE(TextFormat::ParseFromString(
+      "name: \"custom_options_import.proto\" "
+      "package: \"protobuf_unittest\" "
+      "dependency: \"google/protobuf/unittest_custom_options.proto\" ",
+      &file_proto));
+
+  MockErrorCollector error_collector;
+  EXPECT_FALSE(pool.BuildFileCollectingErrors(file_proto, &error_collector));
+  EXPECT_EQ(
+      "custom_options_import.proto: "
+      "google/protobuf/unittest_custom_options.proto: IMPORT: Import "
+      "google/protobuf/unittest_custom_options.proto is unused.\n",
+      error_collector.text_);
+}
+
+// Verifies that proto files can correctly be parsed, even if the
+// custom options defined in the file are incompatible with those
+// compiled in the binary. See http://b/19276250.
+TEST(CustomOptions, OptionsWithIncompatibleDescriptors) {
+  DescriptorPool pool;
+
+  FileDescriptorProto file_proto;
+  MessageOptions::descriptor()->file()->CopyTo(&file_proto);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+
+  // Create a new file descriptor proto containing a subset of the
+  // messages defined in google/protobuf/unittest_custom_options.proto.
+  file_proto.Clear();
+  file_proto.set_name("unittest_custom_options.proto");
+  file_proto.set_package("protobuf_unittest");
+  file_proto.add_dependency("google/protobuf/descriptor.proto");
+
+  // Add the "required_enum_opt" extension.
+  FieldDescriptorProto* extension = file_proto.add_extension();
+  protobuf_unittest::OldOptionType::descriptor()
+      ->file()
+      ->FindExtensionByName("required_enum_opt")
+      ->CopyTo(extension);
+
+  // Add a test message that uses the "required_enum_opt" option.
+  DescriptorProto* test_message_type = file_proto.add_message_type();
+  protobuf_unittest::TestMessageWithRequiredEnumOption::descriptor()->CopyTo(
+      test_message_type);
+
+  // Instruct the extension to use NewOptionType instead of
+  // OldOptionType, and add the descriptor of NewOptionType.
+  extension->set_type_name(".protobuf_unittest.NewOptionType");
+  DescriptorProto* new_option_type = file_proto.add_message_type();
+  protobuf_unittest::NewOptionType::descriptor()->CopyTo(new_option_type);
+
+  // Replace the value of the "required_enum_opt" option used in the
+  // test message with an enum value that only exists in NewOptionType.
+  ASSERT_TRUE(
+      TextFormat::ParseFromString("uninterpreted_option { "
+                                  "  name { "
+                                  "    name_part: 'required_enum_opt' "
+                                  "    is_extension: true "
+                                  "  } "
+                                  "  aggregate_value: 'value: NEW_VALUE'"
+                                  "}",
+                                  test_message_type->mutable_options()));
+
+  // Adding the file descriptor to the pool should fail.
+  EXPECT_TRUE(pool.BuildFile(file_proto) == nullptr);
+}
+
+// Test that FileDescriptor::DebugString() formats custom options correctly.
+TEST(CustomOptions, DebugString) {
+  DescriptorPool pool;
+
+  FileDescriptorProto file_proto;
+  MessageOptions::descriptor()->file()->CopyTo(&file_proto);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+
+  // Add "foo.proto":
+  //   import "google/protobuf/descriptor.proto";
+  //   package "protobuf_unittest";
+  //   option (protobuf_unittest.cc_option1) = 1;
+  //   option (protobuf_unittest.cc_option2) = 2;
+  //   extend google.protobuf.FieldOptions {
+  //     optional int32 cc_option1 = 7736974;
+  //     optional int32 cc_option2 = 7736975;
+  //   }
+  ASSERT_TRUE(TextFormat::ParseFromString(
+      "name: \"foo.proto\" "
+      "package: \"protobuf_unittest\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "options { "
+      "  uninterpreted_option { "
+      "    name { "
+      "      name_part: \"protobuf_unittest.cc_option1\" "
+      "      is_extension: true "
+      "    } "
+      "    positive_int_value: 1 "
+      "  } "
+      "  uninterpreted_option { "
+      "    name { "
+      "      name_part: \"protobuf_unittest.cc_option2\" "
+      "      is_extension: true "
+      "    } "
+      "    positive_int_value: 2 "
+      "  } "
+      "} "
+      "extension { "
+      "  name: \"cc_option1\" "
+      "  extendee: \".google.protobuf.FileOptions\" "
+      // This field number is intentionally chosen to be the same as
+      // (.fileopt1) defined in unittest_custom_options.proto (linked
+      // in this test binary). This is to test whether we are messing
+      // generated pool with custom descriptor pools when dealing with
+      // custom options.
+      "  number: 7736974 "
+      "  label: LABEL_OPTIONAL "
+      "  type: TYPE_INT32 "
+      "}"
+      "extension { "
+      "  name: \"cc_option2\" "
+      "  extendee: \".google.protobuf.FileOptions\" "
+      "  number: 7736975 "
+      "  label: LABEL_OPTIONAL "
+      "  type: TYPE_INT32 "
+      "}",
+      &file_proto));
+  const FileDescriptor* descriptor = pool.BuildFile(file_proto);
+  ASSERT_TRUE(descriptor != nullptr);
+
+  EXPECT_EQ(2, descriptor->extension_count());
+
+  ASSERT_EQ(
+      "syntax = \"proto2\";\n"
+      "\n"
+      "import \"google/protobuf/descriptor.proto\";\n"
+      "package protobuf_unittest;\n"
+      "\n"
+      "option (.protobuf_unittest.cc_option1) = 1;\n"
+      "option (.protobuf_unittest.cc_option2) = 2;\n"
+      "\n"
+      "extend .google.protobuf.FileOptions {\n"
+      "  optional int32 cc_option1 = 7736974;\n"
+      "  optional int32 cc_option2 = 7736975;\n"
+      "}\n"
+      "\n",
+      descriptor->DebugString());
+}
+
+// ===================================================================
+
+class ValidationErrorTest : public testing::Test {
+ protected:
+  // Parse file_text as a FileDescriptorProto in text format and add it
+  // to the DescriptorPool.  Expect no errors.
+  const FileDescriptor* BuildFile(const std::string& file_text) {
+    FileDescriptorProto file_proto;
+    EXPECT_TRUE(TextFormat::ParseFromString(file_text, &file_proto));
+    return GOOGLE_CHECK_NOTNULL(pool_.BuildFile(file_proto));
+  }
+
+  // Parse file_text as a FileDescriptorProto in text format and add it
+  // to the DescriptorPool.  Expect errors to be produced which match the
+  // given error text.
+  void BuildFileWithErrors(const std::string& file_text,
+                           const std::string& expected_errors) {
+    FileDescriptorProto file_proto;
+    ASSERT_TRUE(TextFormat::ParseFromString(file_text, &file_proto));
+
+    MockErrorCollector error_collector;
+    EXPECT_TRUE(pool_.BuildFileCollectingErrors(file_proto, &error_collector) ==
+                nullptr);
+    EXPECT_EQ(expected_errors, error_collector.text_);
+  }
+
+  // Parse file_text as a FileDescriptorProto in text format and add it
+  // to the DescriptorPool.  Expect errors to be produced which match the
+  // given warning text.
+  void BuildFileWithWarnings(const std::string& file_text,
+                             const std::string& expected_warnings) {
+    FileDescriptorProto file_proto;
+    ASSERT_TRUE(TextFormat::ParseFromString(file_text, &file_proto));
+
+    MockErrorCollector error_collector;
+    EXPECT_TRUE(pool_.BuildFileCollectingErrors(file_proto, &error_collector));
+    EXPECT_EQ(expected_warnings, error_collector.warning_text_);
+  }
+
+  // Builds some already-parsed file in our test pool.
+  void BuildFileInTestPool(const FileDescriptor* file) {
+    FileDescriptorProto file_proto;
+    file->CopyTo(&file_proto);
+    ASSERT_TRUE(pool_.BuildFile(file_proto) != nullptr);
+  }
+
+  // Build descriptor.proto in our test pool. This allows us to extend it in
+  // the test pool, so we can test custom options.
+  void BuildDescriptorMessagesInTestPool() {
+    BuildFileInTestPool(DescriptorProto::descriptor()->file());
+  }
+
+  DescriptorPool pool_;
+};
+
+TEST_F(ValidationErrorTest, AlreadyDefined) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type { name: \"Foo\" }"
+      "message_type { name: \"Foo\" }",
+
+      "foo.proto: Foo: NAME: \"Foo\" is already defined.\n");
+}
+
+TEST_F(ValidationErrorTest, AlreadyDefinedInPackage) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "package: \"foo.bar\" "
+      "message_type { name: \"Foo\" }"
+      "message_type { name: \"Foo\" }",
+
+      "foo.proto: foo.bar.Foo: NAME: \"Foo\" is already defined in "
+      "\"foo.bar\".\n");
+}
+
+TEST_F(ValidationErrorTest, AlreadyDefinedInOtherFile) {
+  BuildFile(
+      "name: \"foo.proto\" "
+      "message_type { name: \"Foo\" }");
+
+  BuildFileWithErrors(
+      "name: \"bar.proto\" "
+      "message_type { name: \"Foo\" }",
+
+      "bar.proto: Foo: NAME: \"Foo\" is already defined in file "
+      "\"foo.proto\".\n");
+}
+
+TEST_F(ValidationErrorTest, PackageAlreadyDefined) {
+  BuildFile(
+      "name: \"foo.proto\" "
+      "message_type { name: \"foo\" }");
+  BuildFileWithErrors(
+      "name: \"bar.proto\" "
+      "package: \"foo.bar\"",
+
+      "bar.proto: foo: NAME: \"foo\" is already defined (as something other "
+      "than a package) in file \"foo.proto\".\n");
+}
+
+TEST_F(ValidationErrorTest, EnumValueAlreadyDefinedInParent) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type { name: \"Foo\" value { name: \"FOO\" number: 1 } } "
+      "enum_type { name: \"Bar\" value { name: \"FOO\" number: 1 } } ",
+
+      "foo.proto: FOO: NAME: \"FOO\" is already defined.\n"
+      "foo.proto: FOO: NAME: Note that enum values use C++ scoping rules, "
+      "meaning that enum values are siblings of their type, not children of "
+      "it.  Therefore, \"FOO\" must be unique within the global scope, not "
+      "just within \"Bar\".\n");
+}
+
+TEST_F(ValidationErrorTest, EnumValueAlreadyDefinedInParentNonGlobal) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "package: \"pkg\" "
+      "enum_type { name: \"Foo\" value { name: \"FOO\" number: 1 } } "
+      "enum_type { name: \"Bar\" value { name: \"FOO\" number: 1 } } ",
+
+      "foo.proto: pkg.FOO: NAME: \"FOO\" is already defined in \"pkg\".\n"
+      "foo.proto: pkg.FOO: NAME: Note that enum values use C++ scoping rules, "
+      "meaning that enum values are siblings of their type, not children of "
+      "it.  Therefore, \"FOO\" must be unique within \"pkg\", not just within "
+      "\"Bar\".\n");
+}
+
+TEST_F(ValidationErrorTest, MissingName) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type { }",
+
+      "foo.proto: : NAME: Missing name.\n");
+}
+
+TEST_F(ValidationErrorTest, InvalidName) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type { name: \"$\" }",
+
+      "foo.proto: $: NAME: \"$\" is not a valid identifier.\n");
+}
+
+TEST_F(ValidationErrorTest, InvalidPackageName) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "package: \"foo.$\"",
+
+      "foo.proto: foo.$: NAME: \"$\" is not a valid identifier.\n");
+}
+
+// 'str' is a static C-style string that may contain '\0'
+#define STATIC_STR(str) std::string((str), sizeof(str) - 1)
+
+TEST_F(ValidationErrorTest, NullCharSymbolName) {
+  BuildFileWithErrors(
+      "name: \"bar.proto\" "
+      "package: \"foo\""
+      "message_type { "
+      "  name: '\\000\\001\\013.Bar' "
+      "  field { name: \"foo\" number:  9 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "} "
+      "}",
+      STATIC_STR("bar.proto: foo.\0\x1\v.Bar: NAME: \"\0\x1\v.Bar\" is not a "
+                 "valid identifier.\nbar.proto: foo.\0\x1\v.Bar: NAME: "
+                 "\"\0\x1\v.Bar\" is not a valid identifier.\nbar.proto: "
+                 "foo.\0\x1\v.Bar: NAME: \"\0\x1\v.Bar\" is not a valid "
+                 "identifier.\nbar.proto: foo.\0\x1\v.Bar: NAME: "
+                 "\"\0\x1\v.Bar\" is not a valid identifier.\nbar.proto: "
+                 "foo.\0\x1\v.Bar.foo: NAME: \"foo.\0\x1\v.Bar.foo\" contains "
+                 "null character.\nbar.proto: foo.\0\x1\v.Bar: NAME: "
+                 "\"foo.\0\x1\v.Bar\" contains null character.\n"));
+}
+
+TEST_F(ValidationErrorTest, NullCharFileName) {
+  BuildFileWithErrors(
+      "name: \"bar\\000\\001\\013.proto\" "
+      "package: \"outer.foo\"",
+      STATIC_STR("bar\0\x1\v.proto: bar\0\x1\v.proto: NAME: "
+                 "\"bar\0\x1\v.proto\" contains null character.\n"));
+}
+
+TEST_F(ValidationErrorTest, NullCharPackageName) {
+  BuildFileWithErrors(
+      "name: \"bar.proto\" "
+      "package: \"\\000\\001\\013.\"",
+      STATIC_STR("bar.proto: \0\x1\v.: NAME: \"\0\x1\v.\" contains null "
+                 "character.\n"));
+}
+
+TEST_F(ValidationErrorTest, MissingFileName) {
+  BuildFileWithErrors("",
+
+                      ": : OTHER: Missing field: FileDescriptorProto.name.\n");
+}
+
+TEST_F(ValidationErrorTest, DupeDependency) {
+  BuildFile("name: \"foo.proto\"");
+  BuildFileWithErrors(
+      "name: \"bar.proto\" "
+      "dependency: \"foo.proto\" "
+      "dependency: \"foo.proto\" ",
+
+      "bar.proto: foo.proto: IMPORT: Import \"foo.proto\" was listed twice.\n");
+}
+
+TEST_F(ValidationErrorTest, UnknownDependency) {
+  BuildFileWithErrors(
+      "name: \"bar.proto\" "
+      "dependency: \"foo.proto\" ",
+
+      "bar.proto: foo.proto: IMPORT: Import \"foo.proto\" has not been "
+      "loaded.\n");
+}
+
+TEST_F(ValidationErrorTest, InvalidPublicDependencyIndex) {
+  BuildFile("name: \"foo.proto\"");
+  BuildFileWithErrors(
+      "name: \"bar.proto\" "
+      "dependency: \"foo.proto\" "
+      "public_dependency: 1",
+      "bar.proto: bar.proto: OTHER: Invalid public dependency index.\n");
+}
+
+TEST_F(ValidationErrorTest, ForeignUnimportedPackageNoCrash) {
+  // Used to crash:  If we depend on a non-existent file and then refer to a
+  // package defined in a file that we didn't import, and that package is
+  // nested within a parent package which this file is also in, and we don't
+  // include that parent package in the name (i.e. we do a relative lookup)...
+  // Yes, really.
+  BuildFile(
+      "name: 'foo.proto' "
+      "package: 'outer.foo' ");
+  BuildFileWithErrors(
+      "name: 'bar.proto' "
+      "dependency: 'baz.proto' "
+      "package: 'outer.bar' "
+      "message_type { "
+      "  name: 'Bar' "
+      "  field { name:'bar' number:1 label:LABEL_OPTIONAL type_name:'foo.Foo' }"
+      "}",
+
+      "bar.proto: baz.proto: IMPORT: Import \"baz.proto\" has not been "
+      "loaded.\n"
+      "bar.proto: outer.bar.Bar.bar: TYPE: \"outer.foo\" seems to be defined "
+      "in "
+      "\"foo.proto\", which is not imported by \"bar.proto\".  To use it here, "
+      "please add the necessary import.\n");
+}
+
+TEST_F(ValidationErrorTest, DupeFile) {
+  BuildFile(
+      "name: \"foo.proto\" "
+      "message_type { name: \"Foo\" }");
+  // Note:  We should *not* get redundant errors about "Foo" already being
+  //   defined.
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type { name: \"Foo\" } "
+      // Add another type so that the files aren't identical (in which case
+      // there would be no error).
+      "enum_type { name: \"Bar\" }",
+
+      "foo.proto: foo.proto: OTHER: A file with this name is already in the "
+      "pool.\n");
+}
+
+TEST_F(ValidationErrorTest, FieldInExtensionRange) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name: \"foo\" number:  9 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "}"
+      "  field { name: \"bar\" number: 10 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "}"
+      "  field { name: \"baz\" number: 19 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "}"
+      "  field { name: \"qux\" number: 20 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "}"
+      "  extension_range { start: 10 end: 20 }"
+      "}",
+
+      "foo.proto: Foo.bar: NUMBER: Extension range 10 to 19 includes field "
+      "\"bar\" (10).\n"
+      "foo.proto: Foo.baz: NUMBER: Extension range 10 to 19 includes field "
+      "\"baz\" (19).\n");
+}
+
+TEST_F(ValidationErrorTest, OverlappingExtensionRanges) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  extension_range { start: 10 end: 20 }"
+      "  extension_range { start: 20 end: 30 }"
+      "  extension_range { start: 19 end: 21 }"
+      "}",
+
+      "foo.proto: Foo: NUMBER: Extension range 19 to 20 overlaps with "
+      "already-defined range 10 to 19.\n"
+      "foo.proto: Foo: NUMBER: Extension range 19 to 20 overlaps with "
+      "already-defined range 20 to 29.\n");
+}
+
+TEST_F(ValidationErrorTest, ReservedFieldError) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name: \"foo\" number: 15 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "}"
+      "  reserved_range { start: 10 end: 20 }"
+      "}",
+
+      "foo.proto: Foo.foo: NUMBER: Field \"foo\" uses reserved number 15.\n");
+}
+
+TEST_F(ValidationErrorTest, ReservedExtensionRangeError) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  extension_range { start: 10 end: 20 }"
+      "  reserved_range { start: 5 end: 15 }"
+      "}",
+
+      "foo.proto: Foo: NUMBER: Extension range 10 to 19"
+      " overlaps with reserved range 5 to 14.\n");
+}
+
+TEST_F(ValidationErrorTest, ReservedExtensionRangeAdjacent) {
+  BuildFile(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  extension_range { start: 10 end: 20 }"
+      "  reserved_range { start: 5 end: 10 }"
+      "}");
+}
+
+TEST_F(ValidationErrorTest, ReservedRangeOverlap) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  reserved_range { start: 10 end: 20 }"
+      "  reserved_range { start: 5 end: 15 }"
+      "}",
+
+      "foo.proto: Foo: NUMBER: Reserved range 5 to 14"
+      " overlaps with already-defined range 10 to 19.\n");
+}
+
+TEST_F(ValidationErrorTest, ReservedNameError) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name: \"foo\" number: 15 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "}"
+      "  field { name: \"bar\" number: 16 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "}"
+      "  field { name: \"baz\" number: 17 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "}"
+      "  reserved_name: \"foo\""
+      "  reserved_name: \"bar\""
+      "}",
+
+      "foo.proto: Foo.foo: NAME: Field name \"foo\" is reserved.\n"
+      "foo.proto: Foo.bar: NAME: Field name \"bar\" is reserved.\n");
+}
+
+TEST_F(ValidationErrorTest, ReservedNameRedundant) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  reserved_name: \"foo\""
+      "  reserved_name: \"foo\""
+      "}",
+
+      "foo.proto: foo: NAME: Field name \"foo\" is reserved multiple times.\n");
+}
+
+TEST_F(ValidationErrorTest, ReservedFieldsDebugString) {
+  const FileDescriptor* file = BuildFile(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  reserved_name: \"foo\""
+      "  reserved_name: \"bar\""
+      "  reserved_range { start: 5 end: 6 }"
+      "  reserved_range { start: 10 end: 20 }"
+      "}");
+
+  ASSERT_EQ(
+      "syntax = \"proto2\";\n\n"
+      "message Foo {\n"
+      "  reserved 5, 10 to 19;\n"
+      "  reserved \"foo\", \"bar\";\n"
+      "}\n\n",
+      file->DebugString());
+}
+
+TEST_F(ValidationErrorTest, DebugStringReservedRangeMax) {
+  const FileDescriptor* file = BuildFile(strings::Substitute(
+      "name: \"foo.proto\" "
+      "enum_type { "
+      "  name: \"Bar\""
+      "  value { name:\"BAR\" number:1 }"
+      "  reserved_range { start: 5 end: $0 }"
+      "}"
+      "message_type {"
+      "  name: \"Foo\""
+      "  reserved_range { start: 5 end: $1 }"
+      "}",
+      std::numeric_limits<int>::max(), FieldDescriptor::kMaxNumber + 1));
+
+  ASSERT_EQ(
+      "syntax = \"proto2\";\n\n"
+      "enum Bar {\n"
+      "  BAR = 1;\n"
+      "  reserved 5 to max;\n"
+      "}\n\n"
+      "message Foo {\n"
+      "  reserved 5 to max;\n"
+      "}\n\n",
+      file->DebugString());
+}
+
+TEST_F(ValidationErrorTest, EnumReservedFieldError) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type {"
+      "  name: \"Foo\""
+      "  value { name:\"BAR\" number:15 }"
+      "  reserved_range { start: 10 end: 20 }"
+      "}",
+
+      "foo.proto: BAR: NUMBER: Enum value \"BAR\" uses reserved number 15.\n");
+}
+
+TEST_F(ValidationErrorTest, EnumNegativeReservedFieldError) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type {"
+      "  name: \"Foo\""
+      "  value { name:\"BAR\" number:-15 }"
+      "  reserved_range { start: -20 end: -10 }"
+      "}",
+
+      "foo.proto: BAR: NUMBER: Enum value \"BAR\" uses reserved number -15.\n");
+}
+
+TEST_F(ValidationErrorTest, EnumReservedRangeOverlap) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type {"
+      "  name: \"Foo\""
+      "  value { name:\"BAR\" number:0 }"
+      "  reserved_range { start: 10 end: 20 }"
+      "  reserved_range { start: 5 end: 15 }"
+      "}",
+
+      "foo.proto: Foo: NUMBER: Reserved range 5 to 15"
+      " overlaps with already-defined range 10 to 20.\n");
+}
+
+TEST_F(ValidationErrorTest, EnumReservedRangeOverlapByOne) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type {"
+      "  name: \"Foo\""
+      "  value { name:\"BAR\" number:0 }"
+      "  reserved_range { start: 10 end: 20 }"
+      "  reserved_range { start: 5 end: 10 }"
+      "}",
+
+      "foo.proto: Foo: NUMBER: Reserved range 5 to 10"
+      " overlaps with already-defined range 10 to 20.\n");
+}
+
+TEST_F(ValidationErrorTest, EnumNegativeReservedRangeOverlap) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type {"
+      "  name: \"Foo\""
+      "  value { name:\"BAR\" number:0 }"
+      "  reserved_range { start: -20 end: -10 }"
+      "  reserved_range { start: -15 end: -5 }"
+      "}",
+
+      "foo.proto: Foo: NUMBER: Reserved range -15 to -5"
+      " overlaps with already-defined range -20 to -10.\n");
+}
+
+TEST_F(ValidationErrorTest, EnumMixedReservedRangeOverlap) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type {"
+      "  name: \"Foo\""
+      "  value { name:\"BAR\" number:20 }"
+      "  reserved_range { start: -20 end: 10 }"
+      "  reserved_range { start: -15 end: 5 }"
+      "}",
+
+      "foo.proto: Foo: NUMBER: Reserved range -15 to 5"
+      " overlaps with already-defined range -20 to 10.\n");
+}
+
+TEST_F(ValidationErrorTest, EnumMixedReservedRangeOverlap2) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type {"
+      "  name: \"Foo\""
+      "  value { name:\"BAR\" number:20 }"
+      "  reserved_range { start: -20 end: 10 }"
+      "  reserved_range { start: 10 end: 10 }"
+      "}",
+
+      "foo.proto: Foo: NUMBER: Reserved range 10 to 10"
+      " overlaps with already-defined range -20 to 10.\n");
+}
+
+TEST_F(ValidationErrorTest, EnumReservedRangeStartGreaterThanEnd) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type {"
+      "  name: \"Foo\""
+      "  value { name:\"BAR\" number:20 }"
+      "  reserved_range { start: 11 end: 10 }"
+      "}",
+
+      "foo.proto: Foo: NUMBER: Reserved range end number must be greater"
+      " than start number.\n");
+}
+
+TEST_F(ValidationErrorTest, EnumReservedNameError) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type {"
+      "  name: \"Foo\""
+      "  value { name:\"FOO\" number:15 }"
+      "  value { name:\"BAR\" number:15 }"
+      "  reserved_name: \"FOO\""
+      "  reserved_name: \"BAR\""
+      "}",
+
+      "foo.proto: FOO: NAME: Enum value \"FOO\" is reserved.\n"
+      "foo.proto: BAR: NAME: Enum value \"BAR\" is reserved.\n");
+}
+
+TEST_F(ValidationErrorTest, EnumReservedNameRedundant) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type {"
+      "  name: \"Foo\""
+      "  value { name:\"FOO\" number:15 }"
+      "  reserved_name: \"foo\""
+      "  reserved_name: \"foo\""
+      "}",
+
+      "foo.proto: foo: NAME: Enum value \"foo\" is reserved multiple times.\n");
+}
+
+TEST_F(ValidationErrorTest, EnumReservedFieldsDebugString) {
+  const FileDescriptor* file = BuildFile(
+      "name: \"foo.proto\" "
+      "enum_type {"
+      "  name: \"Foo\""
+      "  value { name:\"FOO\" number:3 }"
+      "  reserved_name: \"foo\""
+      "  reserved_name: \"bar\""
+      "  reserved_range { start: -6 end: -6 }"
+      "  reserved_range { start: -5 end: -4 }"
+      "  reserved_range { start: -1 end: 1 }"
+      "  reserved_range { start: 5 end: 5 }"
+      "  reserved_range { start: 10 end: 19 }"
+      "}");
+
+  ASSERT_EQ(
+      "syntax = \"proto2\";\n\n"
+      "enum Foo {\n"
+      "  FOO = 3;\n"
+      "  reserved -6, -5 to -4, -1 to 1, 5, 10 to 19;\n"
+      "  reserved \"foo\", \"bar\";\n"
+      "}\n\n",
+      file->DebugString());
+}
+
+TEST_F(ValidationErrorTest, InvalidDefaults) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+
+      // Invalid number.
+      "  field { name: \"foo\" number: 1 label: LABEL_OPTIONAL type: TYPE_INT32"
+      "          default_value: \"abc\" }"
+
+      // Empty default value.
+      "  field { name: \"bar\" number: 2 label: LABEL_OPTIONAL type: TYPE_INT32"
+      "          default_value: \"\" }"
+
+      // Invalid boolean.
+      "  field { name: \"baz\" number: 3 label: LABEL_OPTIONAL type: TYPE_BOOL"
+      "          default_value: \"abc\" }"
+
+      // Messages can't have defaults.
+      "  field { name: \"qux\" number: 4 label: LABEL_OPTIONAL type: "
+      "TYPE_MESSAGE"
+      "          default_value: \"abc\" type_name: \"Foo\" }"
+
+      // Same thing, but we don't know that this field has message type until
+      // we look up the type name.
+      "  field { name: \"quux\" number: 5 label: LABEL_OPTIONAL"
+      "          default_value: \"abc\" type_name: \"Foo\" }"
+
+      // Repeateds can't have defaults.
+      "  field { name: \"corge\" number: 6 label: LABEL_REPEATED type: "
+      "TYPE_INT32"
+      "          default_value: \"1\" }"
+      "}",
+
+      "foo.proto: Foo.foo: DEFAULT_VALUE: Couldn't parse default value "
+      "\"abc\".\n"
+      "foo.proto: Foo.bar: DEFAULT_VALUE: Couldn't parse default value \"\".\n"
+      "foo.proto: Foo.baz: DEFAULT_VALUE: Boolean default must be true or "
+      "false.\n"
+      "foo.proto: Foo.qux: DEFAULT_VALUE: Messages can't have default values.\n"
+      "foo.proto: Foo.corge: DEFAULT_VALUE: Repeated fields can't have default "
+      "values.\n"
+      // This ends up being reported later because the error is detected at
+      // cross-linking time.
+      "foo.proto: Foo.quux: DEFAULT_VALUE: Messages can't have default "
+      "values.\n");
+}
+
+TEST_F(ValidationErrorTest, NegativeFieldNumber) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name: \"foo\" number: -1 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "}"
+      "}",
+
+      "foo.proto: Foo.foo: NUMBER: Field numbers must be positive integers.\n");
+}
+
+TEST_F(ValidationErrorTest, HugeFieldNumber) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name: \"foo\" number: 0x70000000 "
+      "          label:LABEL_OPTIONAL type:TYPE_INT32 }"
+      "}",
+
+      "foo.proto: Foo.foo: NUMBER: Field numbers cannot be greater than "
+      "536870911.\n");
+}
+
+TEST_F(ValidationErrorTest, ReservedFieldNumber) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field {name:\"foo\" number: 18999 label:LABEL_OPTIONAL "
+      "type:TYPE_INT32 }"
+      "  field {name:\"bar\" number: 19000 label:LABEL_OPTIONAL "
+      "type:TYPE_INT32 }"
+      "  field {name:\"baz\" number: 19999 label:LABEL_OPTIONAL "
+      "type:TYPE_INT32 }"
+      "  field {name:\"qux\" number: 20000 label:LABEL_OPTIONAL "
+      "type:TYPE_INT32 }"
+      "}",
+
+      "foo.proto: Foo.bar: NUMBER: Field numbers 19000 through 19999 are "
+      "reserved for the protocol buffer library implementation.\n"
+      "foo.proto: Foo.baz: NUMBER: Field numbers 19000 through 19999 are "
+      "reserved for the protocol buffer library implementation.\n");
+}
+
+TEST_F(ValidationErrorTest, ExtensionMissingExtendee) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  extension { name: \"foo\" number: 1 label: LABEL_OPTIONAL"
+      "              type_name: \"Foo\" }"
+      "}",
+
+      "foo.proto: Foo.foo: EXTENDEE: FieldDescriptorProto.extendee not set for "
+      "extension field.\n");
+}
+
+TEST_F(ValidationErrorTest, NonExtensionWithExtendee) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Bar\""
+      "  extension_range { start: 1 end: 2 }"
+      "}"
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name: \"foo\" number: 1 label: LABEL_OPTIONAL"
+      "          type_name: \"Foo\" extendee: \"Bar\" }"
+      "}",
+
+      "foo.proto: Foo.foo: EXTENDEE: FieldDescriptorProto.extendee set for "
+      "non-extension field.\n");
+}
+
+TEST_F(ValidationErrorTest, FieldOneofIndexTooLarge) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "          oneof_index: 1 }"
+      "  field { name:\"dummy\" number:2 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "          oneof_index: 0 }"
+      "  oneof_decl { name:\"bar\" }"
+      "}",
+
+      "foo.proto: Foo.foo: TYPE: FieldDescriptorProto.oneof_index 1 is out of "
+      "range for type \"Foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, FieldOneofIndexNegative) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "          oneof_index: -1 }"
+      "  field { name:\"dummy\" number:2 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "          oneof_index: 0 }"
+      "  oneof_decl { name:\"bar\" }"
+      "}",
+
+      "foo.proto: Foo.foo: TYPE: FieldDescriptorProto.oneof_index -1 is out "
+      "of "
+      "range for type \"Foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, OneofFieldsConsecutiveDefinition) {
+  // Fields belonging to the same oneof must be defined consecutively.
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo1\" number: 1 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "          oneof_index: 0 }"
+      "  field { name:\"bar\" number: 2 label:LABEL_OPTIONAL type:TYPE_INT32 }"
+      "  field { name:\"foo2\" number: 3 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "          oneof_index: 0 }"
+      "  oneof_decl { name:\"foos\" }"
+      "}",
+
+      "foo.proto: Foo.bar: TYPE: Fields in the same oneof must be defined "
+      "consecutively. \"bar\" cannot be defined before the completion of the "
+      "\"foos\" oneof definition.\n");
+
+  // Prevent interleaved fields, which belong to different oneofs.
+  BuildFileWithErrors(
+      "name: \"foo2.proto\" "
+      "message_type {"
+      "  name: \"Foo2\""
+      "  field { name:\"foo1\" number: 1 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "          oneof_index: 0 }"
+      "  field { name:\"bar1\" number: 2 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "          oneof_index: 1 }"
+      "  field { name:\"foo2\" number: 3 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "          oneof_index: 0 }"
+      "  field { name:\"bar2\" number: 4 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "          oneof_index: 1 }"
+      "  oneof_decl { name:\"foos\" }"
+      "  oneof_decl { name:\"bars\" }"
+      "}",
+      "foo2.proto: Foo2.bar1: TYPE: Fields in the same oneof must be defined "
+      "consecutively. \"bar1\" cannot be defined before the completion of the "
+      "\"foos\" oneof definition.\n"
+      "foo2.proto: Foo2.foo2: TYPE: Fields in the same oneof must be defined "
+      "consecutively. \"foo2\" cannot be defined before the completion of the "
+      "\"bars\" oneof definition.\n");
+
+  // Another case for normal fields and different oneof fields interleave.
+  BuildFileWithErrors(
+      "name: \"foo3.proto\" "
+      "message_type {"
+      "  name: \"Foo3\""
+      "  field { name:\"foo1\" number: 1 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "          oneof_index: 0 }"
+      "  field { name:\"bar1\" number: 2 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "          oneof_index: 1 }"
+      "  field { name:\"baz\" number: 3 label:LABEL_OPTIONAL type:TYPE_INT32 }"
+      "  field { name:\"foo2\" number: 4 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "          oneof_index: 0 }"
+      "  oneof_decl { name:\"foos\" }"
+      "  oneof_decl { name:\"bars\" }"
+      "}",
+      "foo3.proto: Foo3.baz: TYPE: Fields in the same oneof must be defined "
+      "consecutively. \"baz\" cannot be defined before the completion of the "
+      "\"foos\" oneof definition.\n");
+}
+
+TEST_F(ValidationErrorTest, FieldNumberConflict) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name: \"foo\" number: 1 label:LABEL_OPTIONAL type:TYPE_INT32 }"
+      "  field { name: \"bar\" number: 1 label:LABEL_OPTIONAL type:TYPE_INT32 }"
+      "}",
+
+      "foo.proto: Foo.bar: NUMBER: Field number 1 has already been used in "
+      "\"Foo\" by field \"foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, BadMessageSetExtensionType) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"MessageSet\""
+      "  options { message_set_wire_format: true }"
+      "  extension_range { start: 4 end: 5 }"
+      "}"
+      "message_type {"
+      "  name: \"Foo\""
+      "  extension { name:\"foo\" number:4 label:LABEL_OPTIONAL type:TYPE_INT32"
+      "              extendee: \"MessageSet\" }"
+      "}",
+
+      "foo.proto: Foo.foo: TYPE: Extensions of MessageSets must be optional "
+      "messages.\n");
+}
+
+TEST_F(ValidationErrorTest, BadMessageSetExtensionLabel) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"MessageSet\""
+      "  options { message_set_wire_format: true }"
+      "  extension_range { start: 4 end: 5 }"
+      "}"
+      "message_type {"
+      "  name: \"Foo\""
+      "  extension { name:\"foo\" number:4 label:LABEL_REPEATED "
+      "type:TYPE_MESSAGE"
+      "              type_name: \"Foo\" extendee: \"MessageSet\" }"
+      "}",
+
+      "foo.proto: Foo.foo: TYPE: Extensions of MessageSets must be optional "
+      "messages.\n");
+}
+
+TEST_F(ValidationErrorTest, FieldInMessageSet) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  options { message_set_wire_format: true }"
+      "  field { name: \"foo\" number: 1 label:LABEL_OPTIONAL type:TYPE_INT32 }"
+      "}",
+
+      "foo.proto: Foo.foo: NAME: MessageSets cannot have fields, only "
+      "extensions.\n");
+}
+
+TEST_F(ValidationErrorTest, NegativeExtensionRangeNumber) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  extension_range { start: -10 end: -1 }"
+      "}",
+
+      "foo.proto: Foo: NUMBER: Extension numbers must be positive integers.\n");
+}
+
+TEST_F(ValidationErrorTest, HugeExtensionRangeNumber) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  extension_range { start: 1 end: 0x70000000 }"
+      "}",
+
+      "foo.proto: Foo: NUMBER: Extension numbers cannot be greater than "
+      "536870911.\n");
+}
+
+TEST_F(ValidationErrorTest, ExtensionRangeEndBeforeStart) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  extension_range { start: 10 end: 10 }"
+      "  extension_range { start: 10 end: 5 }"
+      "}",
+
+      "foo.proto: Foo: NUMBER: Extension range end number must be greater than "
+      "start number.\n"
+      "foo.proto: Foo: NUMBER: Extension range end number must be greater than "
+      "start number.\n");
+}
+
+TEST_F(ValidationErrorTest, EmptyEnum) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type { name: \"Foo\" }"
+      // Also use the empty enum in a message to make sure there are no crashes
+      // during validation (possible if the code attempts to derive a default
+      // value for the field).
+      "message_type {"
+      "  name: \"Bar\""
+      "  field { name: \"foo\" number: 1 label:LABEL_OPTIONAL "
+      "type_name:\"Foo\" }"
+      "  field { name: \"bar\" number: 2 label:LABEL_OPTIONAL "
+      "type_name:\"Foo\" "
+      "          default_value: \"NO_SUCH_VALUE\" }"
+      "}",
+
+      "foo.proto: Foo: NAME: Enums must contain at least one value.\n"
+      "foo.proto: Bar.bar: DEFAULT_VALUE: Enum type \"Foo\" has no value named "
+      "\"NO_SUCH_VALUE\".\n");
+}
+
+TEST_F(ValidationErrorTest, UndefinedExtendee) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  extension { name:\"foo\" number:1 label:LABEL_OPTIONAL type:TYPE_INT32"
+      "              extendee: \"Bar\" }"
+      "}",
+
+      "foo.proto: Foo.foo: EXTENDEE: \"Bar\" is not defined.\n");
+}
+
+TEST_F(ValidationErrorTest, NonMessageExtendee) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type { name: \"Bar\" value { name:\"DUMMY\" number:0 } }"
+      "message_type {"
+      "  name: \"Foo\""
+      "  extension { name:\"foo\" number:1 label:LABEL_OPTIONAL type:TYPE_INT32"
+      "              extendee: \"Bar\" }"
+      "}",
+
+      "foo.proto: Foo.foo: EXTENDEE: \"Bar\" is not a message type.\n");
+}
+
+TEST_F(ValidationErrorTest, NotAnExtensionNumber) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Bar\""
+      "}"
+      "message_type {"
+      "  name: \"Foo\""
+      "  extension { name:\"foo\" number:1 label:LABEL_OPTIONAL type:TYPE_INT32"
+      "              extendee: \"Bar\" }"
+      "}",
+
+      "foo.proto: Foo.foo: NUMBER: \"Bar\" does not declare 1 as an extension "
+      "number.\n");
+}
+
+TEST_F(ValidationErrorTest, RequiredExtension) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Bar\""
+      "  extension_range { start: 1000 end: 10000 }"
+      "}"
+      "message_type {"
+      "  name: \"Foo\""
+      "  extension {"
+      "    name:\"foo\""
+      "    number:1000"
+      "    label:LABEL_REQUIRED"
+      "    type:TYPE_INT32"
+      "    extendee: \"Bar\""
+      "  }"
+      "}",
+
+      "foo.proto: Foo.foo: TYPE: The extension Foo.foo cannot be required.\n");
+}
+
+TEST_F(ValidationErrorTest, UndefinedFieldType) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type_name:\"Bar\" }"
+      "}",
+
+      "foo.proto: Foo.foo: TYPE: \"Bar\" is not defined.\n");
+}
+
+TEST_F(ValidationErrorTest, UndefinedFieldTypeWithDefault) {
+  // See b/12533582. Previously this failed because the default value was not
+  // accepted by the parser, which assumed an enum type, leading to an unclear
+  // error message. We want this input to yield a validation error instead,
+  // since the unknown type is the primary problem.
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type_name:\"int\" "
+      "          default_value:\"1\" }"
+      "}",
+
+      "foo.proto: Foo.foo: TYPE: \"int\" is not defined.\n");
+}
+
+TEST_F(ValidationErrorTest, UndefinedNestedFieldType) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  nested_type { name:\"Baz\" }"
+      "  field { name:\"foo\" number:1"
+      "          label:LABEL_OPTIONAL"
+      "          type_name:\"Foo.Baz.Bar\" }"
+      "}",
+
+      "foo.proto: Foo.foo: TYPE: \"Foo.Baz.Bar\" is not defined.\n");
+}
+
+TEST_F(ValidationErrorTest, FieldTypeDefinedInUndeclaredDependency) {
+  BuildFile(
+      "name: \"bar.proto\" "
+      "message_type { name: \"Bar\" } ");
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type_name:\"Bar\" }"
+      "}",
+      "foo.proto: Foo.foo: TYPE: \"Bar\" seems to be defined in \"bar.proto\", "
+      "which is not imported by \"foo.proto\".  To use it here, please add the "
+      "necessary import.\n");
+}
+
+TEST_F(ValidationErrorTest, FieldTypeDefinedInIndirectDependency) {
+  // Test for hidden dependencies.
+  //
+  // // bar.proto
+  // message Bar{}
+  //
+  // // forward.proto
+  // import "bar.proto"
+  //
+  // // foo.proto
+  // import "forward.proto"
+  // message Foo {
+  //   optional Bar foo = 1;  // Error, needs to import bar.proto explicitly.
+  // }
+  //
+  BuildFile(
+      "name: \"bar.proto\" "
+      "message_type { name: \"Bar\" }");
+
+  BuildFile(
+      "name: \"forward.proto\""
+      "dependency: \"bar.proto\"");
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"forward.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type_name:\"Bar\" }"
+      "}",
+      "foo.proto: Foo.foo: TYPE: \"Bar\" seems to be defined in \"bar.proto\", "
+      "which is not imported by \"foo.proto\".  To use it here, please add the "
+      "necessary import.\n");
+}
+
+TEST_F(ValidationErrorTest, FieldTypeDefinedInPublicDependency) {
+  // Test for public dependencies.
+  //
+  // // bar.proto
+  // message Bar{}
+  //
+  // // forward.proto
+  // import public "bar.proto"
+  //
+  // // foo.proto
+  // import "forward.proto"
+  // message Foo {
+  //   optional Bar foo = 1;  // Correct. "bar.proto" is public imported into
+  //                          // forward.proto, so when "foo.proto" imports
+  //                          // "forward.proto", it imports "bar.proto" too.
+  // }
+  //
+  BuildFile(
+      "name: \"bar.proto\" "
+      "message_type { name: \"Bar\" }");
+
+  BuildFile(
+      "name: \"forward.proto\""
+      "dependency: \"bar.proto\" "
+      "public_dependency: 0");
+
+  BuildFile(
+      "name: \"foo.proto\" "
+      "dependency: \"forward.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type_name:\"Bar\" }"
+      "}");
+}
+
+TEST_F(ValidationErrorTest, FieldTypeDefinedInTransitivePublicDependency) {
+  // Test for public dependencies.
+  //
+  // // bar.proto
+  // message Bar{}
+  //
+  // // forward.proto
+  // import public "bar.proto"
+  //
+  // // forward2.proto
+  // import public "forward.proto"
+  //
+  // // foo.proto
+  // import "forward2.proto"
+  // message Foo {
+  //   optional Bar foo = 1;  // Correct, public imports are transitive.
+  // }
+  //
+  BuildFile(
+      "name: \"bar.proto\" "
+      "message_type { name: \"Bar\" }");
+
+  BuildFile(
+      "name: \"forward.proto\""
+      "dependency: \"bar.proto\" "
+      "public_dependency: 0");
+
+  BuildFile(
+      "name: \"forward2.proto\""
+      "dependency: \"forward.proto\" "
+      "public_dependency: 0");
+
+  BuildFile(
+      "name: \"foo.proto\" "
+      "dependency: \"forward2.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type_name:\"Bar\" }"
+      "}");
+}
+
+TEST_F(ValidationErrorTest,
+       FieldTypeDefinedInPrivateDependencyOfPublicDependency) {
+  // Test for public dependencies.
+  //
+  // // bar.proto
+  // message Bar{}
+  //
+  // // forward.proto
+  // import "bar.proto"
+  //
+  // // forward2.proto
+  // import public "forward.proto"
+  //
+  // // foo.proto
+  // import "forward2.proto"
+  // message Foo {
+  //   optional Bar foo = 1;  // Error, the "bar.proto" is not public imported
+  //                          // into "forward.proto", so will not be imported
+  //                          // into either "forward2.proto" or "foo.proto".
+  // }
+  //
+  BuildFile(
+      "name: \"bar.proto\" "
+      "message_type { name: \"Bar\" }");
+
+  BuildFile(
+      "name: \"forward.proto\""
+      "dependency: \"bar.proto\"");
+
+  BuildFile(
+      "name: \"forward2.proto\""
+      "dependency: \"forward.proto\" "
+      "public_dependency: 0");
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"forward2.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type_name:\"Bar\" }"
+      "}",
+      "foo.proto: Foo.foo: TYPE: \"Bar\" seems to be defined in \"bar.proto\", "
+      "which is not imported by \"foo.proto\".  To use it here, please add the "
+      "necessary import.\n");
+}
+
+
+TEST_F(ValidationErrorTest, SearchMostLocalFirst) {
+  // The following should produce an error that Bar.Baz is resolved but
+  // not defined:
+  //   message Bar { message Baz {} }
+  //   message Foo {
+  //     message Bar {
+  //       // Placing "message Baz{}" here, or removing Foo.Bar altogether,
+  //       // would fix the error.
+  //     }
+  //     optional Bar.Baz baz = 1;
+  //   }
+  // An one point the lookup code incorrectly did not produce an error in this
+  // case, because when looking for Bar.Baz, it would try "Foo.Bar.Baz" first,
+  // fail, and ten try "Bar.Baz" and succeed, even though "Bar" should actually
+  // refer to the inner Bar, not the outer one.
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Bar\""
+      "  nested_type { name: \"Baz\" }"
+      "}"
+      "message_type {"
+      "  name: \"Foo\""
+      "  nested_type { name: \"Bar\" }"
+      "  field { name:\"baz\" number:1 label:LABEL_OPTIONAL"
+      "          type_name:\"Bar.Baz\" }"
+      "}",
+
+      "foo.proto: Foo.baz: TYPE: \"Bar.Baz\" is resolved to \"Foo.Bar.Baz\","
+      " which is not defined. The innermost scope is searched first in name "
+      "resolution. Consider using a leading '.'(i.e., \".Bar.Baz\") to start "
+      "from the outermost scope.\n");
+}
+
+TEST_F(ValidationErrorTest, SearchMostLocalFirst2) {
+  // This test would find the most local "Bar" first, and does, but
+  // proceeds to find the outer one because the inner one's not an
+  // aggregate.
+  BuildFile(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Bar\""
+      "  nested_type { name: \"Baz\" }"
+      "}"
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name: \"Bar\" number:1 type:TYPE_BYTES } "
+      "  field { name:\"baz\" number:2 label:LABEL_OPTIONAL"
+      "          type_name:\"Bar.Baz\" }"
+      "}");
+}
+
+TEST_F(ValidationErrorTest, PackageOriginallyDeclaredInTransitiveDependent) {
+  // Imagine we have the following:
+  //
+  // foo.proto:
+  //   package foo.bar;
+  // bar.proto:
+  //   package foo.bar;
+  //   import "foo.proto";
+  //   message Bar {}
+  // baz.proto:
+  //   package foo;
+  //   import "bar.proto"
+  //   message Baz { optional bar.Bar qux = 1; }
+  //
+  // When validating baz.proto, we will look up "bar.Bar".  As part of this
+  // lookup, we first lookup "bar" then try to find "Bar" within it.  "bar"
+  // should resolve to "foo.bar".  Note, though, that "foo.bar" was originally
+  // defined in foo.proto, which is not a direct dependency of baz.proto.  The
+  // implementation of FindSymbol() normally only returns symbols in direct
+  // dependencies, not indirect ones.  This test insures that this does not
+  // prevent it from finding "foo.bar".
+
+  BuildFile(
+      "name: \"foo.proto\" "
+      "package: \"foo.bar\" ");
+  BuildFile(
+      "name: \"bar.proto\" "
+      "package: \"foo.bar\" "
+      "dependency: \"foo.proto\" "
+      "message_type { name: \"Bar\" }");
+  BuildFile(
+      "name: \"baz.proto\" "
+      "package: \"foo\" "
+      "dependency: \"bar.proto\" "
+      "message_type { "
+      "  name: \"Baz\" "
+      "  field { name:\"qux\" number:1 label:LABEL_OPTIONAL "
+      "          type_name:\"bar.Bar\" }"
+      "}");
+}
+
+TEST_F(ValidationErrorTest, FieldTypeNotAType) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL "
+      "          type_name:\".Foo.bar\" }"
+      "  field { name:\"bar\" number:2 label:LABEL_OPTIONAL type:TYPE_INT32 }"
+      "}",
+
+      "foo.proto: Foo.foo: TYPE: \".Foo.bar\" is not a type.\n");
+}
+
+TEST_F(ValidationErrorTest, RelativeFieldTypeNotAType) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  nested_type {"
+      "    name: \"Bar\""
+      "    field { name:\"Baz\" number:2 label:LABEL_OPTIONAL type:TYPE_INT32 }"
+      "  }"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL "
+      "          type_name:\"Bar.Baz\" }"
+      "}",
+      "foo.proto: Foo.foo: TYPE: \"Bar.Baz\" is not a type.\n");
+}
+
+TEST_F(ValidationErrorTest, FieldTypeMayBeItsName) {
+  BuildFile(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Bar\""
+      "}"
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"Bar\" number:1 label:LABEL_OPTIONAL type_name:\"Bar\" }"
+      "}");
+}
+
+TEST_F(ValidationErrorTest, EnumFieldTypeIsMessage) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type { name: \"Bar\" } "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type:TYPE_ENUM"
+      "          type_name:\"Bar\" }"
+      "}",
+
+      "foo.proto: Foo.foo: TYPE: \"Bar\" is not an enum type.\n");
+}
+
+TEST_F(ValidationErrorTest, MessageFieldTypeIsEnum) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type { name: \"Bar\" value { name:\"DUMMY\" number:0 } } "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type:TYPE_MESSAGE"
+      "          type_name:\"Bar\" }"
+      "}",
+
+      "foo.proto: Foo.foo: TYPE: \"Bar\" is not a message type.\n");
+}
+
+TEST_F(ValidationErrorTest, BadEnumDefaultValue) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type { name: \"Bar\" value { name:\"DUMMY\" number:0 } } "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type_name:\"Bar\""
+      "          default_value:\"NO_SUCH_VALUE\" }"
+      "}",
+
+      "foo.proto: Foo.foo: DEFAULT_VALUE: Enum type \"Bar\" has no value named "
+      "\"NO_SUCH_VALUE\".\n");
+}
+
+TEST_F(ValidationErrorTest, EnumDefaultValueIsInteger) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type { name: \"Bar\" value { name:\"DUMMY\" number:0 } } "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type_name:\"Bar\""
+      "          default_value:\"0\" }"
+      "}",
+
+      "foo.proto: Foo.foo: DEFAULT_VALUE: Default value for an enum field must "
+      "be an identifier.\n");
+}
+
+TEST_F(ValidationErrorTest, PrimitiveWithTypeName) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type:TYPE_INT32"
+      "          type_name:\"Foo\" }"
+      "}",
+
+      "foo.proto: Foo.foo: TYPE: Field with primitive type has type_name.\n");
+}
+
+TEST_F(ValidationErrorTest, NonPrimitiveWithoutTypeName) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type:TYPE_MESSAGE }"
+      "}",
+
+      "foo.proto: Foo.foo: TYPE: Field with message or enum type missing "
+      "type_name.\n");
+}
+
+TEST_F(ValidationErrorTest, OneofWithNoFields) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  oneof_decl { name:\"bar\" }"
+      "}",
+
+      "foo.proto: Foo.bar: NAME: Oneof must have at least one field.\n");
+}
+
+TEST_F(ValidationErrorTest, OneofLabelMismatch) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  field { name:\"foo\" number:1 label:LABEL_REPEATED type:TYPE_INT32 "
+      "          oneof_index:0 }"
+      "  oneof_decl { name:\"bar\" }"
+      "}",
+
+      "foo.proto: Foo.foo: NAME: Fields of oneofs must themselves have label "
+      "LABEL_OPTIONAL.\n");
+}
+
+TEST_F(ValidationErrorTest, InputTypeNotDefined) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type { name: \"Foo\" } "
+      "service {"
+      "  name: \"TestService\""
+      "  method { name: \"A\" input_type: \"Bar\" output_type: \"Foo\" }"
+      "}",
+
+      "foo.proto: TestService.A: INPUT_TYPE: \"Bar\" is not defined.\n"
+  );
+}
+
+TEST_F(ValidationErrorTest, InputTypeNotAMessage) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type { name: \"Foo\" } "
+      "enum_type { name: \"Bar\" value { name:\"DUMMY\" number:0 } } "
+      "service {"
+      "  name: \"TestService\""
+      "  method { name: \"A\" input_type: \"Bar\" output_type: \"Foo\" }"
+      "}",
+
+      "foo.proto: TestService.A: INPUT_TYPE: \"Bar\" is not a message type.\n"
+  );
+}
+
+TEST_F(ValidationErrorTest, OutputTypeNotDefined) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type { name: \"Foo\" } "
+      "service {"
+      "  name: \"TestService\""
+      "  method { name: \"A\" input_type: \"Foo\" output_type: \"Bar\" }"
+      "}",
+
+      "foo.proto: TestService.A: OUTPUT_TYPE: \"Bar\" is not defined.\n"
+  );
+}
+
+TEST_F(ValidationErrorTest, OutputTypeNotAMessage) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type { name: \"Foo\" } "
+      "enum_type { name: \"Bar\" value { name:\"DUMMY\" number:0 } } "
+      "service {"
+      "  name: \"TestService\""
+      "  method { name: \"A\" input_type: \"Foo\" output_type: \"Bar\" }"
+      "}",
+
+      "foo.proto: TestService.A: OUTPUT_TYPE: \"Bar\" is not a message type.\n"
+  );
+}
+
+
+TEST_F(ValidationErrorTest, IllegalPackedField) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {\n"
+      "  name: \"Foo\""
+      "  field { name:\"packed_string\" number:1 label:LABEL_REPEATED "
+      "          type:TYPE_STRING "
+      "          options { uninterpreted_option {"
+      "            name { name_part: \"packed\" is_extension: false }"
+      "            identifier_value: \"true\" }}}\n"
+      "  field { name:\"packed_message\" number:3 label:LABEL_REPEATED "
+      "          type_name: \"Foo\""
+      "          options { uninterpreted_option {"
+      "            name { name_part: \"packed\" is_extension: false }"
+      "            identifier_value: \"true\" }}}\n"
+      "  field { name:\"optional_int32\" number: 4 label: LABEL_OPTIONAL "
+      "          type:TYPE_INT32 "
+      "          options { uninterpreted_option {"
+      "            name { name_part: \"packed\" is_extension: false }"
+      "            identifier_value: \"true\" }}}\n"
+      "}",
+
+      "foo.proto: Foo.packed_string: TYPE: [packed = true] can only be "
+      "specified for repeated primitive fields.\n"
+      "foo.proto: Foo.packed_message: TYPE: [packed = true] can only be "
+      "specified for repeated primitive fields.\n"
+      "foo.proto: Foo.optional_int32: TYPE: [packed = true] can only be "
+      "specified for repeated primitive fields.\n");
+}
+
+TEST_F(ValidationErrorTest, OptionWrongType) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type { "
+      "  name: \"TestMessage\" "
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type:TYPE_STRING "
+      "          options { uninterpreted_option { name { name_part: \"ctype\" "
+      "                                                  is_extension: false }"
+      "                                           positive_int_value: 1 }"
+      "          }"
+      "  }"
+      "}\n",
+
+      "foo.proto: TestMessage.foo: OPTION_VALUE: Value must be identifier for "
+      "enum-valued option \"google.protobuf.FieldOptions.ctype\".\n");
+}
+
+TEST_F(ValidationErrorTest, OptionExtendsAtomicType) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type { "
+      "  name: \"TestMessage\" "
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type:TYPE_STRING "
+      "          options { uninterpreted_option { name { name_part: \"ctype\" "
+      "                                                  is_extension: false }"
+      "                                           name { name_part: \"foo\" "
+      "                                                  is_extension: true }"
+      "                                           positive_int_value: 1 }"
+      "          }"
+      "  }"
+      "}\n",
+
+      "foo.proto: TestMessage.foo: OPTION_NAME: Option \"ctype\" is an "
+      "atomic type, not a message.\n");
+}
+
+TEST_F(ValidationErrorTest, DupOption) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type { "
+      "  name: \"TestMessage\" "
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type:TYPE_UINT32 "
+      "          options { uninterpreted_option { name { name_part: \"ctype\" "
+      "                                                  is_extension: false }"
+      "                                           identifier_value: \"CORD\" }"
+      "                    uninterpreted_option { name { name_part: \"ctype\" "
+      "                                                  is_extension: false }"
+      "                                           identifier_value: \"CORD\" }"
+      "          }"
+      "  }"
+      "}\n",
+
+      "foo.proto: TestMessage.foo: OPTION_NAME: Option \"ctype\" was "
+      "already set.\n");
+}
+
+TEST_F(ValidationErrorTest, InvalidOptionName) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type { "
+      "  name: \"TestMessage\" "
+      "  field { name:\"foo\" number:1 label:LABEL_OPTIONAL type:TYPE_BOOL "
+      "          options { uninterpreted_option { "
+      "                      name { name_part: \"uninterpreted_option\" "
+      "                             is_extension: false }"
+      "                      positive_int_value: 1 "
+      "                    }"
+      "          }"
+      "  }"
+      "}\n",
+
+      "foo.proto: TestMessage.foo: OPTION_NAME: Option must not use "
+      "reserved name \"uninterpreted_option\".\n");
+}
+
+TEST_F(ValidationErrorTest, RepeatedMessageOption) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "message_type: { name: \"Bar\" field: { "
+      "  name: \"foo\" number: 1 label: LABEL_OPTIONAL type: TYPE_INT32 } "
+      "} "
+      "extension { name: \"bar\" number: 7672757 label: LABEL_REPEATED "
+      "            type: TYPE_MESSAGE type_name: \"Bar\" "
+      "            extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"bar\" "
+      "                                        is_extension: true } "
+      "                                 name { name_part: \"foo\" "
+      "                                        is_extension: false } "
+      "                                 positive_int_value: 1 } }",
+
+      "foo.proto: foo.proto: OPTION_NAME: Option field \"(bar)\" is a "
+      "repeated message. Repeated message options must be initialized "
+      "using an aggregate value.\n");
+}
+
+TEST_F(ValidationErrorTest, ResolveUndefinedOption) {
+  // The following should produce an error that baz.bar is resolved but not
+  // defined.
+  // foo.proto:
+  //   package baz
+  //   import google/protobuf/descriptor.proto
+  //   message Bar { optional int32 foo = 1; }
+  //   extend FileOptions { optional Bar bar = 7672757; }
+  //
+  // qux.proto:
+  //   package qux.baz
+  //   option (baz.bar).foo = 1;
+  //
+  // Although "baz.bar" is already defined, the lookup code will try
+  // "qux.baz.bar", since it's the match from the innermost scope, which will
+  // cause a symbol not defined error.
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFile(
+      "name: \"foo.proto\" "
+      "package: \"baz\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "message_type: { name: \"Bar\" field: { "
+      "  name: \"foo\" number: 1 label: LABEL_OPTIONAL type: TYPE_INT32 } "
+      "} "
+      "extension { name: \"bar\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_MESSAGE type_name: \"Bar\" "
+      "            extendee: \"google.protobuf.FileOptions\" }");
+
+  BuildFileWithErrors(
+      "name: \"qux.proto\" "
+      "package: \"qux.baz\" "
+      "options { uninterpreted_option { name { name_part: \"baz.bar\" "
+      "                                        is_extension: true } "
+      "                                 name { name_part: \"foo\" "
+      "                                        is_extension: false } "
+      "                                 positive_int_value: 1 } }",
+
+      "qux.proto: qux.proto: OPTION_NAME: Option \"(baz.bar)\" is resolved to "
+      "\"(qux.baz.bar)\","
+      " which is not defined. The innermost scope is searched first in name "
+      "resolution. Consider using a leading '.'(i.e., \"(.baz.bar)\") to start "
+      "from the outermost scope.\n");
+}
+
+TEST_F(ValidationErrorTest, UnknownOption) {
+  BuildFileWithErrors(
+      "name: \"qux.proto\" "
+      "package: \"qux.baz\" "
+      "options { uninterpreted_option { name { name_part: \"baaz.bar\" "
+      "                                        is_extension: true } "
+      "                                 name { name_part: \"foo\" "
+      "                                        is_extension: false } "
+      "                                 positive_int_value: 1 } }",
+
+      "qux.proto: qux.proto: OPTION_NAME: Option \"(baaz.bar)\" unknown. "
+      "Ensure "
+      "that your proto definition file imports the proto which defines the "
+      "option.\n");
+}
+
+TEST_F(ValidationErrorTest, CustomOptionConflictingFieldNumber) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "extension { name: \"foo1\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_INT32 extendee: \"google.protobuf.FieldOptions\" }"
+      "extension { name: \"foo2\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_INT32 extendee: \"google.protobuf.FieldOptions\" }",
+
+      "foo.proto: foo2: NUMBER: Extension number 7672757 has already been used "
+      "in \"google.protobuf.FieldOptions\" by extension \"foo1\".\n");
+}
+
+TEST_F(ValidationErrorTest, Int32OptionValueOutOfPositiveRange) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "extension { name: \"foo\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_INT32 extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"foo\" "
+      "                                        is_extension: true } "
+      "                                 positive_int_value: 0x80000000 } "
+      "}",
+
+      "foo.proto: foo.proto: OPTION_VALUE: Value out of range "
+      "for int32 option \"foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, Int32OptionValueOutOfNegativeRange) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "extension { name: \"foo\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_INT32 extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"foo\" "
+      "                                        is_extension: true } "
+      "                                 negative_int_value: -0x80000001 } "
+      "}",
+
+      "foo.proto: foo.proto: OPTION_VALUE: Value out of range "
+      "for int32 option \"foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, Int32OptionValueIsNotPositiveInt) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "extension { name: \"foo\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_INT32 extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"foo\" "
+      "                                        is_extension: true } "
+      "                                 string_value: \"5\" } }",
+
+      "foo.proto: foo.proto: OPTION_VALUE: Value must be integer "
+      "for int32 option \"foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, Int64OptionValueOutOfRange) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "extension { name: \"foo\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_INT64 extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"foo\" "
+      "                                        is_extension: true } "
+      "                                 positive_int_value: 0x8000000000000000 "
+      "} "
+      "}",
+
+      "foo.proto: foo.proto: OPTION_VALUE: Value out of range "
+      "for int64 option \"foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, Int64OptionValueIsNotPositiveInt) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "extension { name: \"foo\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_INT64 extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"foo\" "
+      "                                        is_extension: true } "
+      "                                 identifier_value: \"5\" } }",
+
+      "foo.proto: foo.proto: OPTION_VALUE: Value must be integer "
+      "for int64 option \"foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, UInt32OptionValueOutOfRange) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "extension { name: \"foo\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_UINT32 extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"foo\" "
+      "                                        is_extension: true } "
+      "                                 positive_int_value: 0x100000000 } }",
+
+      "foo.proto: foo.proto: OPTION_VALUE: Value out of range "
+      "for uint32 option \"foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, UInt32OptionValueIsNotPositiveInt) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "extension { name: \"foo\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_UINT32 extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"foo\" "
+      "                                        is_extension: true } "
+      "                                 double_value: -5.6 } }",
+
+      "foo.proto: foo.proto: OPTION_VALUE: Value must be non-negative integer "
+      "for uint32 option \"foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, UInt64OptionValueIsNotPositiveInt) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "extension { name: \"foo\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_UINT64 extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"foo\" "
+      "                                        is_extension: true } "
+      "                                 negative_int_value: -5 } }",
+
+      "foo.proto: foo.proto: OPTION_VALUE: Value must be non-negative integer "
+      "for uint64 option \"foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, FloatOptionValueIsNotNumber) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "extension { name: \"foo\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_FLOAT extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"foo\" "
+      "                                        is_extension: true } "
+      "                                 string_value: \"bar\" } }",
+
+      "foo.proto: foo.proto: OPTION_VALUE: Value must be number "
+      "for float option \"foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, DoubleOptionValueIsNotNumber) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "extension { name: \"foo\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_DOUBLE extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"foo\" "
+      "                                        is_extension: true } "
+      "                                 string_value: \"bar\" } }",
+
+      "foo.proto: foo.proto: OPTION_VALUE: Value must be number "
+      "for double option \"foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, BoolOptionValueIsNotTrueOrFalse) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "extension { name: \"foo\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_BOOL extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"foo\" "
+      "                                        is_extension: true } "
+      "                                 identifier_value: \"bar\" } }",
+
+      "foo.proto: foo.proto: OPTION_VALUE: Value must be \"true\" or \"false\" "
+      "for boolean option \"foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, EnumOptionValueIsNotIdentifier) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "enum_type { name: \"FooEnum\" value { name: \"BAR\" number: 1 } "
+      "                              value { name: \"BAZ\" number: 2 } }"
+      "extension { name: \"foo\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_ENUM type_name: \"FooEnum\" "
+      "            extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"foo\" "
+      "                                        is_extension: true } "
+      "                                 string_value: \"QUUX\" } }",
+
+      "foo.proto: foo.proto: OPTION_VALUE: Value must be identifier for "
+      "enum-valued option \"foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, EnumOptionValueIsNotEnumValueName) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "enum_type { name: \"FooEnum\" value { name: \"BAR\" number: 1 } "
+      "                              value { name: \"BAZ\" number: 2 } }"
+      "extension { name: \"foo\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_ENUM type_name: \"FooEnum\" "
+      "            extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"foo\" "
+      "                                        is_extension: true } "
+      "                                 identifier_value: \"QUUX\" } }",
+
+      "foo.proto: foo.proto: OPTION_VALUE: Enum type \"FooEnum\" has no value "
+      "named \"QUUX\" for option \"foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, EnumOptionValueIsSiblingEnumValueName) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "enum_type { name: \"FooEnum1\" value { name: \"BAR\" number: 1 } "
+      "                               value { name: \"BAZ\" number: 2 } }"
+      "enum_type { name: \"FooEnum2\" value { name: \"QUX\" number: 1 } "
+      "                               value { name: \"QUUX\" number: 2 } }"
+      "extension { name: \"foo\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_ENUM type_name: \"FooEnum1\" "
+      "            extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"foo\" "
+      "                                        is_extension: true } "
+      "                                 identifier_value: \"QUUX\" } }",
+
+      "foo.proto: foo.proto: OPTION_VALUE: Enum type \"FooEnum1\" has no value "
+      "named \"QUUX\" for option \"foo\". This appears to be a value from a "
+      "sibling type.\n");
+}
+
+TEST_F(ValidationErrorTest, StringOptionValueIsNotString) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "extension { name: \"foo\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_STRING extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"foo\" "
+      "                                        is_extension: true } "
+      "                                 identifier_value: \"QUUX\" } }",
+
+      "foo.proto: foo.proto: OPTION_VALUE: Value must be quoted string "
+      "for "
+      "string option \"foo\".\n");
+}
+
+TEST_F(ValidationErrorTest, JsonNameOptionOnExtensions) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "package: \"foo\" "
+      "message_type {"
+      "  name: \"Foo\""
+      "  extension_range { start: 10 end: 20 }"
+      "}"
+      "extension {"
+      "  name: \"value\""
+      "  number: 10"
+      "  label: LABEL_OPTIONAL"
+      "  type: TYPE_INT32"
+      "  extendee: \"foo.Foo\""
+      "  json_name: \"myName\""
+      "}",
+      "foo.proto: foo.value: OPTION_NAME: option json_name is not allowed on "
+      "extension fields.\n");
+}
+
+TEST_F(ValidationErrorTest, DuplicateExtensionFieldNumber) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFile(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "extension { name: \"option1\" number: 1000 label: LABEL_OPTIONAL "
+      "            type: TYPE_INT32 extendee: \"google.protobuf.FileOptions\" }");
+
+  BuildFileWithWarnings(
+      "name: \"bar.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "extension { name: \"option2\" number: 1000 label: LABEL_OPTIONAL "
+      "            type: TYPE_INT32 extendee: \"google.protobuf.FileOptions\" }",
+      "bar.proto: option2: NUMBER: Extension number 1000 has already been used "
+      "in \"google.protobuf.FileOptions\" by extension \"option1\" defined in "
+      "foo.proto.\n");
+}
+
+// Helper function for tests that check for aggregate value parsing
+// errors.  The "value" argument is embedded inside the
+// "uninterpreted_option" portion of the result.
+static std::string EmbedAggregateValue(const char* value) {
+  return strings::Substitute(
+      "name: \"foo.proto\" "
+      "dependency: \"google/protobuf/descriptor.proto\" "
+      "message_type { name: \"Foo\" } "
+      "extension { name: \"foo\" number: 7672757 label: LABEL_OPTIONAL "
+      "            type: TYPE_MESSAGE type_name: \"Foo\" "
+      "            extendee: \"google.protobuf.FileOptions\" }"
+      "options { uninterpreted_option { name { name_part: \"foo\" "
+      "                                        is_extension: true } "
+      "                                 $0 } }",
+      value);
+}
+
+TEST_F(ValidationErrorTest, AggregateValueNotFound) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      EmbedAggregateValue("string_value: \"\""),
+      "foo.proto: foo.proto: OPTION_VALUE: Option \"foo\" is a message. "
+      "To set the entire message, use syntax like "
+      "\"foo = { <proto text format> }\". To set fields within it, use "
+      "syntax like \"foo.foo = value\".\n");
+}
+
+TEST_F(ValidationErrorTest, AggregateValueParseError) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      EmbedAggregateValue("aggregate_value: \"1+2\""),
+      "foo.proto: foo.proto: OPTION_VALUE: Error while parsing option "
+      "value for \"foo\": Expected identifier, got: 1\n");
+}
+
+TEST_F(ValidationErrorTest, AggregateValueUnknownFields) {
+  BuildDescriptorMessagesInTestPool();
+
+  BuildFileWithErrors(
+      EmbedAggregateValue("aggregate_value: \"x:100\""),
+      "foo.proto: foo.proto: OPTION_VALUE: Error while parsing option "
+      "value for \"foo\": Message type \"Foo\" has no field named \"x\".\n");
+}
+
+TEST_F(ValidationErrorTest, NotLiteImportsLite) {
+  BuildFile(
+      "name: \"bar.proto\" "
+      "options { optimize_for: LITE_RUNTIME } ");
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"bar.proto\" ",
+
+      "foo.proto: bar.proto: IMPORT: Files that do not use optimize_for = "
+      "LITE_RUNTIME cannot import files which do use this option.  This file "
+      "is not lite, but it imports \"bar.proto\" which is.\n");
+}
+
+TEST_F(ValidationErrorTest, LiteExtendsNotLite) {
+  BuildFile(
+      "name: \"bar.proto\" "
+      "message_type: {"
+      "  name: \"Bar\""
+      "  extension_range { start: 1 end: 1000 }"
+      "}");
+
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "dependency: \"bar.proto\" "
+      "options { optimize_for: LITE_RUNTIME } "
+      "extension { name: \"ext\" number: 123 label: LABEL_OPTIONAL "
+      "            type: TYPE_INT32 extendee: \"Bar\" }",
+
+      "foo.proto: ext: EXTENDEE: Extensions to non-lite types can only be "
+      "declared in non-lite files.  Note that you cannot extend a non-lite "
+      "type to contain a lite type, but the reverse is allowed.\n");
+}
+
+TEST_F(ValidationErrorTest, NoLiteServices) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "options {"
+      "  optimize_for: LITE_RUNTIME"
+      "  cc_generic_services: true"
+      "  java_generic_services: true"
+      "} "
+      "service { name: \"Foo\" }",
+
+      "foo.proto: Foo: NAME: Files with optimize_for = LITE_RUNTIME cannot "
+      "define services unless you set both options cc_generic_services and "
+      "java_generic_services to false.\n");
+
+  BuildFile(
+      "name: \"bar.proto\" "
+      "options {"
+      "  optimize_for: LITE_RUNTIME"
+      "  cc_generic_services: false"
+      "  java_generic_services: false"
+      "} "
+      "service { name: \"Bar\" }");
+}
+
+TEST_F(ValidationErrorTest, RollbackAfterError) {
+  // Build a file which contains every kind of construct but references an
+  // undefined type.  All these constructs will be added to the symbol table
+  // before the undefined type error is noticed.  The DescriptorPool will then
+  // have to roll everything back.
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"TestMessage\""
+      "  field { name:\"foo\" label:LABEL_OPTIONAL type:TYPE_INT32 number:1 }"
+      "} "
+      "enum_type {"
+      "  name: \"TestEnum\""
+      "  value { name:\"BAR\" number:1 }"
+      "} "
+      "service {"
+      "  name: \"TestService\""
+      "  method {"
+      "    name: \"Baz\""
+      "    input_type: \"NoSuchType\""  // error
+      "    output_type: \"TestMessage\""
+      "  }"
+      "}",
+
+      "foo.proto: TestService.Baz: INPUT_TYPE: \"NoSuchType\" is not defined.\n"
+  );
+
+  // Make sure that if we build the same file again with the error fixed,
+  // it works.  If the above rollback was incomplete, then some symbols will
+  // be left defined, and this second attempt will fail since it tries to
+  // re-define the same symbols.
+  BuildFile(
+      "name: \"foo.proto\" "
+      "message_type {"
+      "  name: \"TestMessage\""
+      "  field { name:\"foo\" label:LABEL_OPTIONAL type:TYPE_INT32 number:1 }"
+      "} "
+      "enum_type {"
+      "  name: \"TestEnum\""
+      "  value { name:\"BAR\" number:1 }"
+      "} "
+      "service {"
+      "  name: \"TestService\""
+      "  method { name:\"Baz\""
+      "           input_type:\"TestMessage\""
+      "           output_type:\"TestMessage\" }"
+      "}");
+}
+
+TEST_F(ValidationErrorTest, ErrorsReportedToLogError) {
+  // Test that errors are reported to GOOGLE_LOG(ERROR) if no error collector is
+  // provided.
+
+  FileDescriptorProto file_proto;
+  ASSERT_TRUE(
+      TextFormat::ParseFromString("name: \"foo.proto\" "
+                                  "message_type { name: \"Foo\" } "
+                                  "message_type { name: \"Foo\" } ",
+                                  &file_proto));
+
+  std::vector<std::string> errors;
+
+  {
+    ScopedMemoryLog log;
+    EXPECT_TRUE(pool_.BuildFile(file_proto) == nullptr);
+    errors = log.GetMessages(ERROR);
+  }
+
+  ASSERT_EQ(2, errors.size());
+
+  EXPECT_EQ("Invalid proto descriptor for file \"foo.proto\":", errors[0]);
+  EXPECT_EQ("  Foo: \"Foo\" is already defined.", errors[1]);
+}
+
+TEST_F(ValidationErrorTest, DisallowEnumAlias) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type {"
+      "  name: \"Bar\""
+      "  value { name:\"ENUM_A\" number:0 }"
+      "  value { name:\"ENUM_B\" number:0 }"
+      "}",
+      "foo.proto: Bar: NUMBER: "
+      "\"ENUM_B\" uses the same enum value as \"ENUM_A\". "
+      "If this is intended, set 'option allow_alias = true;' to the enum "
+      "definition.\n");
+}
+
+TEST_F(ValidationErrorTest, AllowEnumAlias) {
+  BuildFile(
+      "name: \"foo.proto\" "
+      "enum_type {"
+      "  name: \"Bar\""
+      "  value { name:\"ENUM_A\" number:0 }"
+      "  value { name:\"ENUM_B\" number:0 }"
+      "  options { allow_alias: true }"
+      "}");
+}
+
+TEST_F(ValidationErrorTest, UnusedImportWarning) {
+  pool_.AddUnusedImportTrackFile("bar.proto");
+  BuildFile(
+      "name: \"bar.proto\" "
+      "message_type { name: \"Bar\" }");
+
+  pool_.AddUnusedImportTrackFile("base.proto");
+  BuildFile(
+      "name: \"base.proto\" "
+      "message_type { name: \"Base\" }");
+
+  pool_.AddUnusedImportTrackFile("baz.proto");
+  BuildFile(
+      "name: \"baz.proto\" "
+      "message_type { name: \"Baz\" }");
+
+  pool_.AddUnusedImportTrackFile("public.proto");
+  BuildFile(
+      "name: \"public.proto\" "
+      "dependency: \"bar.proto\""
+      "public_dependency: 0");
+
+  // // forward.proto
+  // import "base.proto"       // No warning: Base message is used.
+  // import "bar.proto"        // Will log a warning.
+  // import public "baz.proto" // No warning: Do not track import public.
+  // import "public.proto"     // No warning: public.proto has import public.
+  // message Forward {
+  //   optional Base base = 1;
+  // }
+  //
+  pool_.AddUnusedImportTrackFile("forward.proto");
+  BuildFileWithWarnings(
+      "name: \"forward.proto\""
+      "dependency: \"base.proto\""
+      "dependency: \"bar.proto\""
+      "dependency: \"baz.proto\""
+      "dependency: \"public.proto\""
+      "public_dependency: 2 "
+      "message_type {"
+      "  name: \"Forward\""
+      "  field { name:\"base\" number:1 label:LABEL_OPTIONAL "
+      "type_name:\"Base\" }"
+      "}",
+      "forward.proto: bar.proto: IMPORT: Import bar.proto is unused.\n");
+}
+
+namespace {
+void FillValidMapEntry(FileDescriptorProto* file_proto) {
+  ASSERT_TRUE(TextFormat::ParseFromString(
+      "name: 'foo.proto' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  field { "
+      "    name: 'foo_map' number: 1 label:LABEL_REPEATED "
+      "    type_name: 'FooMapEntry' "
+      "  } "
+      "  nested_type { "
+      "    name: 'FooMapEntry' "
+      "    options {  map_entry: true } "
+      "    field { "
+      "      name: 'key' number: 1 type:TYPE_INT32 label:LABEL_OPTIONAL "
+      "    } "
+      "    field { "
+      "      name: 'value' number: 2 type:TYPE_INT32 label:LABEL_OPTIONAL "
+      "    } "
+      "  } "
+      "} "
+      "message_type { "
+      "  name: 'Bar' "
+      "  extension_range { start: 1 end: 10 }"
+      "} ",
+      file_proto));
+}
+static const char* kMapEntryErrorMessage =
+    "foo.proto: Foo.foo_map: TYPE: map_entry should not be set explicitly. "
+    "Use map<KeyType, ValueType> instead.\n";
+static const char* kMapEntryKeyTypeErrorMessage =
+    "foo.proto: Foo.foo_map: TYPE: Key in map fields cannot be float/double, "
+    "bytes or message types.\n";
+
+}  // namespace
+
+TEST_F(ValidationErrorTest, MapEntryBase) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  BuildFile(file_proto.DebugString());
+}
+
+TEST_F(ValidationErrorTest, MapEntryExtensionRange) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "extension_range { "
+      "  start: 10 end: 20 "
+      "} ",
+      file_proto.mutable_message_type(0)->mutable_nested_type(0));
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryExtension) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "extension { "
+      "  name: 'foo_ext' extendee: '.Bar' number: 5"
+      "} ",
+      file_proto.mutable_message_type(0)->mutable_nested_type(0));
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryNestedType) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "nested_type { "
+      "  name: 'Bar' "
+      "} ",
+      file_proto.mutable_message_type(0)->mutable_nested_type(0));
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryEnumTypes) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "enum_type { "
+      "  name: 'BarEnum' "
+      "  value { name: 'BAR_BAR' number:0 } "
+      "} ",
+      file_proto.mutable_message_type(0)->mutable_nested_type(0));
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryExtraField) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "field { "
+      "  name: 'other_field' "
+      "  label: LABEL_OPTIONAL "
+      "  type: TYPE_INT32 "
+      "  number: 3 "
+      "} ",
+      file_proto.mutable_message_type(0)->mutable_nested_type(0));
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryMessageName) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  file_proto.mutable_message_type(0)->mutable_nested_type(0)->set_name(
+      "OtherMapEntry");
+  file_proto.mutable_message_type(0)->mutable_field(0)->set_type_name(
+      "OtherMapEntry");
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryNoneRepeatedMapEntry) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  file_proto.mutable_message_type(0)->mutable_field(0)->set_label(
+      FieldDescriptorProto::LABEL_OPTIONAL);
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryDifferentContainingType) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  // Move the nested MapEntry message into the top level, which should not pass
+  // the validation.
+  file_proto.mutable_message_type()->AddAllocated(
+      file_proto.mutable_message_type(0)->mutable_nested_type()->ReleaseLast());
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryKeyName) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* key =
+      file_proto.mutable_message_type(0)->mutable_nested_type(0)->mutable_field(
+          0);
+  key->set_name("Key");
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryKeyLabel) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* key =
+      file_proto.mutable_message_type(0)->mutable_nested_type(0)->mutable_field(
+          0);
+  key->set_label(FieldDescriptorProto::LABEL_REQUIRED);
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryKeyNumber) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* key =
+      file_proto.mutable_message_type(0)->mutable_nested_type(0)->mutable_field(
+          0);
+  key->set_number(3);
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryValueName) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* value =
+      file_proto.mutable_message_type(0)->mutable_nested_type(0)->mutable_field(
+          1);
+  value->set_name("Value");
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryValueLabel) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* value =
+      file_proto.mutable_message_type(0)->mutable_nested_type(0)->mutable_field(
+          1);
+  value->set_label(FieldDescriptorProto::LABEL_REQUIRED);
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryValueNumber) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* value =
+      file_proto.mutable_message_type(0)->mutable_nested_type(0)->mutable_field(
+          1);
+  value->set_number(3);
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryKeyTypeFloat) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* key =
+      file_proto.mutable_message_type(0)->mutable_nested_type(0)->mutable_field(
+          0);
+  key->set_type(FieldDescriptorProto::TYPE_FLOAT);
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryKeyTypeErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryKeyTypeDouble) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* key =
+      file_proto.mutable_message_type(0)->mutable_nested_type(0)->mutable_field(
+          0);
+  key->set_type(FieldDescriptorProto::TYPE_DOUBLE);
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryKeyTypeErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryKeyTypeBytes) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* key =
+      file_proto.mutable_message_type(0)->mutable_nested_type(0)->mutable_field(
+          0);
+  key->set_type(FieldDescriptorProto::TYPE_BYTES);
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryKeyTypeErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryKeyTypeEnum) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* key =
+      file_proto.mutable_message_type(0)->mutable_nested_type(0)->mutable_field(
+          0);
+  key->clear_type();
+  key->set_type_name("BarEnum");
+  EnumDescriptorProto* enum_proto = file_proto.add_enum_type();
+  enum_proto->set_name("BarEnum");
+  EnumValueDescriptorProto* enum_value_proto = enum_proto->add_value();
+  enum_value_proto->set_name("BAR_VALUE0");
+  enum_value_proto->set_number(0);
+  BuildFileWithErrors(file_proto.DebugString(),
+                      "foo.proto: Foo.foo_map: TYPE: Key in map fields cannot "
+                      "be enum types.\n");
+  // Enum keys are not allowed in proto3 as well.
+  // Get rid of extensions for proto3 to make it proto3 compatible.
+  file_proto.mutable_message_type()->RemoveLast();
+  file_proto.set_syntax("proto3");
+  BuildFileWithErrors(file_proto.DebugString(),
+                      "foo.proto: Foo.foo_map: TYPE: Key in map fields cannot "
+                      "be enum types.\n");
+}
+
+TEST_F(ValidationErrorTest, MapEntryKeyTypeMessage) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* key =
+      file_proto.mutable_message_type(0)->mutable_nested_type(0)->mutable_field(
+          0);
+  key->clear_type();
+  key->set_type_name(".Bar");
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryKeyTypeErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryConflictsWithField) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "field { "
+      "  name: 'FooMapEntry' "
+      "  type: TYPE_INT32 "
+      "  label: LABEL_OPTIONAL "
+      "  number: 100 "
+      "}",
+      file_proto.mutable_message_type(0));
+  BuildFileWithErrors(
+      file_proto.DebugString(),
+      "foo.proto: Foo.FooMapEntry: NAME: \"FooMapEntry\" is already defined in "
+      "\"Foo\".\n"
+      "foo.proto: Foo.foo_map: TYPE: \"FooMapEntry\" is not defined.\n"
+      "foo.proto: Foo: NAME: Expanded map entry type FooMapEntry conflicts "
+      "with an existing field.\n");
+}
+
+TEST_F(ValidationErrorTest, MapEntryConflictsWithMessage) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "nested_type { "
+      "  name: 'FooMapEntry' "
+      "}",
+      file_proto.mutable_message_type(0));
+  BuildFileWithErrors(
+      file_proto.DebugString(),
+      "foo.proto: Foo.FooMapEntry: NAME: \"FooMapEntry\" is already defined in "
+      "\"Foo\".\n"
+      "foo.proto: Foo: NAME: Expanded map entry type FooMapEntry conflicts "
+      "with an existing nested message type.\n");
+}
+
+TEST_F(ValidationErrorTest, MapEntryConflictsWithEnum) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "enum_type { "
+      "  name: 'FooMapEntry' "
+      "  value { name: 'ENTRY_FOO' number: 0 }"
+      "}",
+      file_proto.mutable_message_type(0));
+  BuildFileWithErrors(
+      file_proto.DebugString(),
+      "foo.proto: Foo.FooMapEntry: NAME: \"FooMapEntry\" is already defined in "
+      "\"Foo\".\n"
+      "foo.proto: Foo: NAME: Expanded map entry type FooMapEntry conflicts "
+      "with an existing enum type.\n");
+}
+
+TEST_F(ValidationErrorTest, EnumValuesConflictWithDifferentCasing) {
+  BuildFileWithErrors(
+      "syntax: 'proto3'"
+      "name: 'foo.proto' "
+      "enum_type {"
+      "  name: 'FooEnum' "
+      "  value { name: 'BAR' number: 0 }"
+      "  value { name: 'bar' number: 1 }"
+      "}",
+      "foo.proto: bar: NAME: Enum name bar has the same name as BAR "
+      "if you ignore case and strip out the enum name prefix (if any). "
+      "This is error-prone and can lead to undefined behavior. "
+      "Please avoid doing this. If you are using allow_alias, please assign "
+      "the same numeric value to both enums.\n");
+
+  // Not an error because both enums are mapped to the same value.
+  BuildFile(
+      "syntax: 'proto3'"
+      "name: 'foo.proto' "
+      "enum_type {"
+      "  name: 'FooEnum' "
+      "  options { allow_alias: true }"
+      "  value { name: 'UNKNOWN' number: 0 }"
+      "  value { name: 'BAR' number: 1 }"
+      "  value { name: 'bar' number: 1 }"
+      "}");
+}
+
+TEST_F(ValidationErrorTest, EnumValuesConflictWhenPrefixesStripped) {
+  BuildFileWithErrors(
+      "syntax: 'proto3'"
+      "name: 'foo.proto' "
+      "enum_type {"
+      "  name: 'FooEnum' "
+      "  value { name: 'FOO_ENUM_BAZ' number: 0 }"
+      "  value { name: 'BAZ' number: 1 }"
+      "}",
+      "foo.proto: BAZ: NAME: Enum name BAZ has the same name as FOO_ENUM_BAZ "
+      "if you ignore case and strip out the enum name prefix (if any). "
+      "This is error-prone and can lead to undefined behavior. "
+      "Please avoid doing this. If you are using allow_alias, please assign "
+      "the same numeric value to both enums.\n");
+
+  BuildFileWithErrors(
+      "syntax: 'proto3'"
+      "name: 'foo.proto' "
+      "enum_type {"
+      "  name: 'FooEnum' "
+      "  value { name: 'FOOENUM_BAZ' number: 0 }"
+      "  value { name: 'BAZ' number: 1 }"
+      "}",
+      "foo.proto: BAZ: NAME: Enum name BAZ has the same name as FOOENUM_BAZ "
+      "if you ignore case and strip out the enum name prefix (if any). "
+      "This is error-prone and can lead to undefined behavior. "
+      "Please avoid doing this. If you are using allow_alias, please assign "
+      "the same numeric value to both enums.\n");
+
+  BuildFileWithErrors(
+      "syntax: 'proto3'"
+      "name: 'foo.proto' "
+      "enum_type {"
+      "  name: 'FooEnum' "
+      "  value { name: 'FOO_ENUM_BAR_BAZ' number: 0 }"
+      "  value { name: 'BAR__BAZ' number: 1 }"
+      "}",
+      "foo.proto: BAR__BAZ: NAME: Enum name BAR__BAZ has the same name as "
+      "FOO_ENUM_BAR_BAZ if you ignore case and strip out the enum name prefix "
+      "(if any). This is error-prone and can lead to undefined behavior. "
+      "Please avoid doing this. If you are using allow_alias, please assign "
+      "the same numeric value to both enums.\n");
+
+  BuildFileWithErrors(
+      "syntax: 'proto3'"
+      "name: 'foo.proto' "
+      "enum_type {"
+      "  name: 'FooEnum' "
+      "  value { name: 'FOO_ENUM__BAR_BAZ' number: 0 }"
+      "  value { name: 'BAR_BAZ' number: 1 }"
+      "}",
+      "foo.proto: BAR_BAZ: NAME: Enum name BAR_BAZ has the same name as "
+      "FOO_ENUM__BAR_BAZ if you ignore case and strip out the enum name prefix "
+      "(if any). This is error-prone and can lead to undefined behavior. "
+      "Please avoid doing this. If you are using allow_alias, please assign "
+      "the same numeric value to both enums.\n");
+
+  // This isn't an error because the underscore will cause the PascalCase to
+  // differ by case (BarBaz vs. Barbaz).
+  BuildFile(
+      "syntax: 'proto3'"
+      "name: 'foo.proto' "
+      "enum_type {"
+      "  name: 'FooEnum' "
+      "  value { name: 'BAR_BAZ' number: 0 }"
+      "  value { name: 'BARBAZ' number: 1 }"
+      "}");
+}
+
+TEST_F(ValidationErrorTest, MapEntryConflictsWithOneof) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "oneof_decl { "
+      "  name: 'FooMapEntry' "
+      "}"
+      "field { "
+      "  name: 'int_field' "
+      "  type: TYPE_INT32 "
+      "  label: LABEL_OPTIONAL "
+      "  oneof_index: 0 "
+      "  number: 100 "
+      "} ",
+      file_proto.mutable_message_type(0));
+  BuildFileWithErrors(
+      file_proto.DebugString(),
+      "foo.proto: Foo.FooMapEntry: NAME: \"FooMapEntry\" is already defined in "
+      "\"Foo\".\n"
+      "foo.proto: Foo.foo_map: TYPE: \"FooMapEntry\" is not defined.\n"
+      "foo.proto: Foo: NAME: Expanded map entry type FooMapEntry conflicts "
+      "with an existing oneof type.\n");
+}
+
+TEST_F(ValidationErrorTest, MapEntryUsesNoneZeroEnumDefaultValue) {
+  BuildFileWithErrors(
+      "name: \"foo.proto\" "
+      "enum_type {"
+      "  name: \"Bar\""
+      "  value { name:\"ENUM_A\" number:1 }"
+      "  value { name:\"ENUM_B\" number:2 }"
+      "}"
+      "message_type {"
+      "  name: 'Foo' "
+      "  field { "
+      "    name: 'foo_map' number: 1 label:LABEL_REPEATED "
+      "    type_name: 'FooMapEntry' "
+      "  } "
+      "  nested_type { "
+      "    name: 'FooMapEntry' "
+      "    options {  map_entry: true } "
+      "    field { "
+      "      name: 'key' number: 1 type:TYPE_INT32 label:LABEL_OPTIONAL "
+      "    } "
+      "    field { "
+      "      name: 'value' number: 2 type_name:\"Bar\" label:LABEL_OPTIONAL "
+      "    } "
+      "  } "
+      "}",
+      "foo.proto: Foo.foo_map: "
+      "TYPE: Enum value in map must define 0 as the first value.\n");
+}
+
+TEST_F(ValidationErrorTest, Proto3RequiredFields) {
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  field { name:'foo' number:1 label:LABEL_REQUIRED type:TYPE_INT32 } "
+      "}",
+      "foo.proto: Foo.foo: TYPE: Required fields are not allowed in "
+      "proto3.\n");
+
+  // applied to nested types as well.
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  nested_type { "
+      "    name : 'Bar' "
+      "    field { name:'bar' number:1 label:LABEL_REQUIRED type:TYPE_INT32 } "
+      "  } "
+      "}",
+      "foo.proto: Foo.Bar.bar: TYPE: Required fields are not allowed in "
+      "proto3.\n");
+
+  // optional and repeated fields are OK.
+  BuildFile(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  field { name:'foo' number:1 label:LABEL_OPTIONAL type:TYPE_INT32 } "
+      "  field { name:'bar' number:2 label:LABEL_REPEATED type:TYPE_INT32 } "
+      "}");
+}
+
+TEST_F(ValidationErrorTest, ValidateProto3DefaultValue) {
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  field { name:'foo' number:1 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "          default_value: '1' }"
+      "}",
+      "foo.proto: Foo.foo: DEFAULT_VALUE: Explicit default values are not "
+      "allowed in proto3.\n");
+
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  nested_type { "
+      "    name : 'Bar' "
+      "    field { name:'bar' number:1 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "            default_value: '1' }"
+      "  } "
+      "}",
+      "foo.proto: Foo.Bar.bar: DEFAULT_VALUE: Explicit default values are not "
+      "allowed in proto3.\n");
+}
+
+TEST_F(ValidationErrorTest, ValidateProto3ExtensionRange) {
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  field { name:'foo' number:1 label:LABEL_OPTIONAL type:TYPE_INT32 } "
+      "  extension_range { start:10 end:100 } "
+      "}",
+      "foo.proto: Foo: NUMBER: Extension ranges are not allowed in "
+      "proto3.\n");
+
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  nested_type { "
+      "    name : 'Bar' "
+      "    field { name:'bar' number:1 label:LABEL_OPTIONAL type:TYPE_INT32 } "
+      "    extension_range { start:10 end:100 } "
+      "  } "
+      "}",
+      "foo.proto: Foo.Bar: NUMBER: Extension ranges are not allowed in "
+      "proto3.\n");
+}
+
+TEST_F(ValidationErrorTest, ValidateProto3MessageSetWireFormat) {
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  options { message_set_wire_format: true } "
+      "}",
+      "foo.proto: Foo: NAME: MessageSet is not supported "
+      "in proto3.\n");
+}
+
+TEST_F(ValidationErrorTest, ValidateProto3Enum) {
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "enum_type { "
+      "  name: 'FooEnum' "
+      "  value { name: 'FOO_FOO' number:1 } "
+      "}",
+      "foo.proto: FooEnum: NUMBER: The first enum value must be "
+      "zero in proto3.\n");
+
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  enum_type { "
+      "    name: 'FooEnum' "
+      "    value { name: 'FOO_FOO' number:1 } "
+      "  } "
+      "}",
+      "foo.proto: Foo.FooEnum: NUMBER: The first enum value must be "
+      "zero in proto3.\n");
+
+  // valid case.
+  BuildFile(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "enum_type { "
+      "  name: 'FooEnum' "
+      "  value { name: 'FOO_FOO' number:0 } "
+      "}");
+}
+
+TEST_F(ValidationErrorTest, ValidateProto3Group) {
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  nested_type { "
+      "    name: 'FooGroup' "
+      "  } "
+      "  field { name:'foo_group' number: 1 label:LABEL_OPTIONAL "
+      "          type: TYPE_GROUP type_name:'FooGroup' } "
+      "}",
+      "foo.proto: Foo.foo_group: TYPE: Groups are not supported in proto3 "
+      "syntax.\n");
+}
+
+
+TEST_F(ValidationErrorTest, ValidateProto3EnumFromProto2) {
+  // Define an enum in a proto2 file.
+  BuildFile(
+      "name: 'foo.proto' "
+      "package: 'foo' "
+      "syntax: 'proto2' "
+      "enum_type { "
+      "  name: 'FooEnum' "
+      "  value { name: 'DEFAULT_OPTION' number:0 } "
+      "}");
+
+  // Now try to refer to it. (All tests in the fixture use the same pool, so we
+  // can refer to the enum above in this definition.)
+  BuildFileWithErrors(
+      "name: 'bar.proto' "
+      "dependency: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "    field { name:'bar' number:1 label:LABEL_OPTIONAL type:TYPE_ENUM "
+      "            type_name: 'foo.FooEnum' }"
+      "}",
+      "bar.proto: Foo.bar: TYPE: Enum type \"foo.FooEnum\" is not a proto3 "
+      "enum, but is used in \"Foo\" which is a proto3 message type.\n");
+}
+
+TEST_F(ValidationErrorTest, ValidateProto3Extension) {
+  // Valid for options.
+  DescriptorPool pool;
+  FileDescriptorProto file_proto;
+  // Add "google/protobuf/descriptor.proto".
+  FileDescriptorProto::descriptor()->file()->CopyTo(&file_proto);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+  // Add "foo.proto":
+  //   import "google/protobuf/descriptor.proto";
+  //   extend google.protobuf.FieldOptions {
+  //     optional int32 option1 = 1000;
+  //   }
+  file_proto.Clear();
+  file_proto.set_name("foo.proto");
+  file_proto.set_syntax("proto3");
+  file_proto.add_dependency("google/protobuf/descriptor.proto");
+  AddExtension(&file_proto, "google.protobuf.FieldOptions", "option1", 1000,
+               FieldDescriptorProto::LABEL_OPTIONAL,
+               FieldDescriptorProto::TYPE_INT32);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != nullptr);
+
+  // Copy and change the package of the descriptor.proto
+  BuildFile(
+      "name: 'google.protobuf.proto' "
+      "syntax: 'proto2' "
+      "message_type { "
+      "  name: 'Container' extension_range { start: 1 end: 1000 } "
+      "}");
+  BuildFileWithErrors(
+      "name: 'bar.proto' "
+      "syntax: 'proto3' "
+      "dependency: 'google.protobuf.proto' "
+      "extension { "
+      "  name: 'bar' number: 1 label: LABEL_OPTIONAL type: TYPE_INT32 "
+      "  extendee: 'Container' "
+      "}",
+      "bar.proto: bar: EXTENDEE: Extensions in proto3 are only allowed for "
+      "defining options.\n");
+}
+
+// Test that field names that may conflict in JSON is not allowed by protoc.
+TEST_F(ValidationErrorTest, ValidateProto3JsonName) {
+  // The comparison is case-insensitive.
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type {"
+      "  name: 'Foo'"
+      "  field { name:'name' number:1 label:LABEL_OPTIONAL type:TYPE_INT32 }"
+      "  field { name:'Name' number:2 label:LABEL_OPTIONAL type:TYPE_INT32 }"
+      "}",
+      "foo.proto: Foo: NAME: The JSON camel-case name of field \"Name\" "
+      "conflicts with field \"name\". This is not allowed in proto3.\n");
+  // Underscores are ignored.
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type {"
+      "  name: 'Foo'"
+      "  field { name:'ab' number:1 label:LABEL_OPTIONAL type:TYPE_INT32 }"
+      "  field { name:'_a__b_' number:2 label:LABEL_OPTIONAL type:TYPE_INT32 }"
+      "}",
+      "foo.proto: Foo: NAME: The JSON camel-case name of field \"_a__b_\" "
+      "conflicts with field \"ab\". This is not allowed in proto3.\n");
+}
+
+
+TEST_F(ValidationErrorTest, UnusedImportWithOtherError) {
+  BuildFile(
+      "name: 'bar.proto' "
+      "message_type {"
+      "  name: 'Bar'"
+      "}");
+
+  pool_.AddUnusedImportTrackFile("foo.proto", true);
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "dependency: 'bar.proto' "
+      "message_type {"
+      "  name: 'Foo'"
+      "  extension { name:'foo' number:1 label:LABEL_OPTIONAL type:TYPE_INT32"
+      "              extendee: 'Baz' }"
+      "}",
+
+      // Should not also contain unused import error.
+      "foo.proto: Foo.foo: EXTENDEE: \"Baz\" is not defined.\n");
+}
+
+
+// ===================================================================
+// DescriptorDatabase
+
+static void AddToDatabase(SimpleDescriptorDatabase* database,
+                          const char* file_text) {
+  FileDescriptorProto file_proto;
+  EXPECT_TRUE(TextFormat::ParseFromString(file_text, &file_proto));
+  database->Add(file_proto);
+}
+
+class DatabaseBackedPoolTest : public testing::Test {
+ protected:
+  DatabaseBackedPoolTest() {}
+
+  SimpleDescriptorDatabase database_;
+
+  void SetUp() override {
+    AddToDatabase(
+        &database_,
+        "name: 'foo.proto' "
+        "message_type { name:'Foo' extension_range { start: 1 end: 100 } } "
+        "enum_type { name:'TestEnum' value { name:'DUMMY' number:0 } } "
+        "service { name:'TestService' } ");
+    AddToDatabase(&database_,
+                  "name: 'bar.proto' "
+                  "dependency: 'foo.proto' "
+                  "message_type { name:'Bar' } "
+                  "extension { name:'foo_ext' extendee: '.Foo' number:5 "
+                  "            label:LABEL_OPTIONAL type:TYPE_INT32 } ");
+    // Baz has an undeclared dependency on Foo.
+    AddToDatabase(
+        &database_,
+        "name: 'baz.proto' "
+        "message_type { "
+        "  name:'Baz' "
+        "  field { name:'foo' number:1 label:LABEL_OPTIONAL type_name:'Foo' } "
+        "}");
+  }
+
+  // We can't inject a file containing errors into a DescriptorPool, so we
+  // need an actual mock DescriptorDatabase to test errors.
+  class ErrorDescriptorDatabase : public DescriptorDatabase {
+   public:
+    ErrorDescriptorDatabase() {}
+    ~ErrorDescriptorDatabase() {}
+
+    // implements DescriptorDatabase ---------------------------------
+    bool FindFileByName(const std::string& filename,
+                        FileDescriptorProto* output) override {
+      // error.proto and error2.proto cyclically import each other.
+      if (filename == "error.proto") {
+        output->Clear();
+        output->set_name("error.proto");
+        output->add_dependency("error2.proto");
+        return true;
+      } else if (filename == "error2.proto") {
+        output->Clear();
+        output->set_name("error2.proto");
+        output->add_dependency("error.proto");
+        return true;
+      } else {
+        return false;
+      }
+    }
+    bool FindFileContainingSymbol(const std::string& symbol_name,
+                                  FileDescriptorProto* output) override {
+      return false;
+    }
+    bool FindFileContainingExtension(const std::string& containing_type,
+                                     int field_number,
+                                     FileDescriptorProto* output) override {
+      return false;
+    }
+  };
+
+  // A DescriptorDatabase that counts how many times each method has been
+  // called and forwards to some other DescriptorDatabase.
+  class CallCountingDatabase : public DescriptorDatabase {
+   public:
+    CallCountingDatabase(DescriptorDatabase* wrapped_db)
+        : wrapped_db_(wrapped_db) {
+      Clear();
+    }
+    ~CallCountingDatabase() {}
+
+    DescriptorDatabase* wrapped_db_;
+
+    int call_count_;
+
+    void Clear() { call_count_ = 0; }
+
+    // implements DescriptorDatabase ---------------------------------
+    bool FindFileByName(const std::string& filename,
+                        FileDescriptorProto* output) override {
+      ++call_count_;
+      return wrapped_db_->FindFileByName(filename, output);
+    }
+    bool FindFileContainingSymbol(const std::string& symbol_name,
+                                  FileDescriptorProto* output) override {
+      ++call_count_;
+      return wrapped_db_->FindFileContainingSymbol(symbol_name, output);
+    }
+    bool FindFileContainingExtension(const std::string& containing_type,
+                                     int field_number,
+                                     FileDescriptorProto* output) override {
+      ++call_count_;
+      return wrapped_db_->FindFileContainingExtension(containing_type,
+                                                      field_number, output);
+    }
+  };
+
+  // A DescriptorDatabase which falsely always returns foo.proto when searching
+  // for any symbol or extension number.  This shouldn't cause the
+  // DescriptorPool to reload foo.proto if it is already loaded.
+  class FalsePositiveDatabase : public DescriptorDatabase {
+   public:
+    FalsePositiveDatabase(DescriptorDatabase* wrapped_db)
+        : wrapped_db_(wrapped_db) {}
+    ~FalsePositiveDatabase() {}
+
+    DescriptorDatabase* wrapped_db_;
+
+    // implements DescriptorDatabase ---------------------------------
+    bool FindFileByName(const std::string& filename,
+                        FileDescriptorProto* output) override {
+      return wrapped_db_->FindFileByName(filename, output);
+    }
+    bool FindFileContainingSymbol(const std::string& symbol_name,
+                                  FileDescriptorProto* output) override {
+      return FindFileByName("foo.proto", output);
+    }
+    bool FindFileContainingExtension(const std::string& containing_type,
+                                     int field_number,
+                                     FileDescriptorProto* output) override {
+      return FindFileByName("foo.proto", output);
+    }
+  };
+};
+
+TEST_F(DatabaseBackedPoolTest, FindFileByName) {
+  DescriptorPool pool(&database_);
+
+  const FileDescriptor* foo = pool.FindFileByName("foo.proto");
+  ASSERT_TRUE(foo != nullptr);
+  EXPECT_EQ("foo.proto", foo->name());
+  ASSERT_EQ(1, foo->message_type_count());
+  EXPECT_EQ("Foo", foo->message_type(0)->name());
+
+  EXPECT_EQ(foo, pool.FindFileByName("foo.proto"));
+
+  EXPECT_TRUE(pool.FindFileByName("no_such_file.proto") == nullptr);
+}
+
+TEST_F(DatabaseBackedPoolTest, FindDependencyBeforeDependent) {
+  DescriptorPool pool(&database_);
+
+  const FileDescriptor* foo = pool.FindFileByName("foo.proto");
+  ASSERT_TRUE(foo != nullptr);
+  EXPECT_EQ("foo.proto", foo->name());
+  ASSERT_EQ(1, foo->message_type_count());
+  EXPECT_EQ("Foo", foo->message_type(0)->name());
+
+  const FileDescriptor* bar = pool.FindFileByName("bar.proto");
+  ASSERT_TRUE(bar != nullptr);
+  EXPECT_EQ("bar.proto", bar->name());
+  ASSERT_EQ(1, bar->message_type_count());
+  EXPECT_EQ("Bar", bar->message_type(0)->name());
+
+  ASSERT_EQ(1, bar->dependency_count());
+  EXPECT_EQ(foo, bar->dependency(0));
+}
+
+TEST_F(DatabaseBackedPoolTest, FindDependentBeforeDependency) {
+  DescriptorPool pool(&database_);
+
+  const FileDescriptor* bar = pool.FindFileByName("bar.proto");
+  ASSERT_TRUE(bar != nullptr);
+  EXPECT_EQ("bar.proto", bar->name());
+  ASSERT_EQ(1, bar->message_type_count());
+  ASSERT_EQ("Bar", bar->message_type(0)->name());
+
+  const FileDescriptor* foo = pool.FindFileByName("foo.proto");
+  ASSERT_TRUE(foo != nullptr);
+  EXPECT_EQ("foo.proto", foo->name());
+  ASSERT_EQ(1, foo->message_type_count());
+  ASSERT_EQ("Foo", foo->message_type(0)->name());
+
+  ASSERT_EQ(1, bar->dependency_count());
+  EXPECT_EQ(foo, bar->dependency(0));
+}
+
+TEST_F(DatabaseBackedPoolTest, FindFileContainingSymbol) {
+  DescriptorPool pool(&database_);
+
+  const FileDescriptor* file = pool.FindFileContainingSymbol("Foo");
+  ASSERT_TRUE(file != nullptr);
+  EXPECT_EQ("foo.proto", file->name());
+  EXPECT_EQ(file, pool.FindFileByName("foo.proto"));
+
+  EXPECT_TRUE(pool.FindFileContainingSymbol("NoSuchSymbol") == nullptr);
+}
+
+TEST_F(DatabaseBackedPoolTest, FindMessageTypeByName) {
+  DescriptorPool pool(&database_);
+
+  const Descriptor* type = pool.FindMessageTypeByName("Foo");
+  ASSERT_TRUE(type != nullptr);
+  EXPECT_EQ("Foo", type->name());
+  EXPECT_EQ(type->file(), pool.FindFileByName("foo.proto"));
+
+  EXPECT_TRUE(pool.FindMessageTypeByName("NoSuchType") == nullptr);
+}
+
+TEST_F(DatabaseBackedPoolTest, FindExtensionByNumber) {
+  DescriptorPool pool(&database_);
+
+  const Descriptor* foo = pool.FindMessageTypeByName("Foo");
+  ASSERT_TRUE(foo != nullptr);
+
+  const FieldDescriptor* extension = pool.FindExtensionByNumber(foo, 5);
+  ASSERT_TRUE(extension != nullptr);
+  EXPECT_EQ("foo_ext", extension->name());
+  EXPECT_EQ(extension->file(), pool.FindFileByName("bar.proto"));
+
+  EXPECT_TRUE(pool.FindExtensionByNumber(foo, 12) == nullptr);
+}
+
+TEST_F(DatabaseBackedPoolTest, FindAllExtensions) {
+  DescriptorPool pool(&database_);
+
+  const Descriptor* foo = pool.FindMessageTypeByName("Foo");
+
+  for (int i = 0; i < 2; ++i) {
+    // Repeat the lookup twice, to check that we get consistent
+    // results despite the fallback database lookup mutating the pool.
+    std::vector<const FieldDescriptor*> extensions;
+    pool.FindAllExtensions(foo, &extensions);
+    ASSERT_EQ(1, extensions.size());
+    EXPECT_EQ(5, extensions[0]->number());
+  }
+}
+
+TEST_F(DatabaseBackedPoolTest, ErrorWithoutErrorCollector) {
+  ErrorDescriptorDatabase error_database;
+  DescriptorPool pool(&error_database);
+
+  std::vector<std::string> errors;
+
+  {
+    ScopedMemoryLog log;
+    EXPECT_TRUE(pool.FindFileByName("error.proto") == nullptr);
+    errors = log.GetMessages(ERROR);
+  }
+
+  EXPECT_FALSE(errors.empty());
+}
+
+TEST_F(DatabaseBackedPoolTest, ErrorWithErrorCollector) {
+  ErrorDescriptorDatabase error_database;
+  MockErrorCollector error_collector;
+  DescriptorPool pool(&error_database, &error_collector);
+
+  EXPECT_TRUE(pool.FindFileByName("error.proto") == nullptr);
+  EXPECT_EQ(
+      "error.proto: error2.proto: IMPORT: File recursively imports itself: "
+      "error.proto -> error2.proto -> error.proto\n"
+      "error2.proto: error.proto: IMPORT: Import \"error.proto\" was not "
+      "found or had errors.\n"
+      "error.proto: error2.proto: IMPORT: Import \"error2.proto\" was not "
+      "found or had errors.\n",
+      error_collector.text_);
+}
+
+TEST_F(DatabaseBackedPoolTest, UndeclaredDependencyOnUnbuiltType) {
+  // Check that we find and report undeclared dependencies on types that exist
+  // in the descriptor database but that have not not been built yet.
+  MockErrorCollector error_collector;
+  DescriptorPool pool(&database_, &error_collector);
+  EXPECT_TRUE(pool.FindMessageTypeByName("Baz") == nullptr);
+  EXPECT_EQ(
+      "baz.proto: Baz.foo: TYPE: \"Foo\" seems to be defined in \"foo.proto\", "
+      "which is not imported by \"baz.proto\".  To use it here, please add "
+      "the necessary import.\n",
+      error_collector.text_);
+}
+
+TEST_F(DatabaseBackedPoolTest, RollbackAfterError) {
+  // Make sure that all traces of bad types are removed from the pool. This used
+  // to be b/4529436, due to the fact that a symbol resolution failure could
+  // potentially cause another file to be recursively built, which would trigger
+  // a checkpoint _past_ possibly invalid symbols.
+  // Baz is defined in the database, but the file is invalid because it is
+  // missing a necessary import.
+  DescriptorPool pool(&database_);
+  EXPECT_TRUE(pool.FindMessageTypeByName("Baz") == nullptr);
+  // Make sure that searching again for the file or the type fails.
+  EXPECT_TRUE(pool.FindFileByName("baz.proto") == nullptr);
+  EXPECT_TRUE(pool.FindMessageTypeByName("Baz") == nullptr);
+}
+
+TEST_F(DatabaseBackedPoolTest, UnittestProto) {
+  // Try to load all of unittest.proto from a DescriptorDatabase.  This should
+  // thoroughly test all paths through DescriptorBuilder to insure that there
+  // are no deadlocking problems when pool_->mutex_ is non-null.
+  const FileDescriptor* original_file =
+      protobuf_unittest::TestAllTypes::descriptor()->file();
+
+  DescriptorPoolDatabase database(*DescriptorPool::generated_pool());
+  DescriptorPool pool(&database);
+  const FileDescriptor* file_from_database =
+      pool.FindFileByName(original_file->name());
+
+  ASSERT_TRUE(file_from_database != nullptr);
+
+  FileDescriptorProto original_file_proto;
+  original_file->CopyTo(&original_file_proto);
+
+  FileDescriptorProto file_from_database_proto;
+  file_from_database->CopyTo(&file_from_database_proto);
+
+  EXPECT_EQ(original_file_proto.DebugString(),
+            file_from_database_proto.DebugString());
+
+  // Also verify that CopyTo() did not omit any information.
+  EXPECT_EQ(original_file->DebugString(), file_from_database->DebugString());
+}
+
+TEST_F(DatabaseBackedPoolTest, DoesntRetryDbUnnecessarily) {
+  // Searching for a child of an existing descriptor should never fall back
+  // to the DescriptorDatabase even if it isn't found, because we know all
+  // children are already loaded.
+  CallCountingDatabase call_counter(&database_);
+  DescriptorPool pool(&call_counter);
+
+  const FileDescriptor* file = pool.FindFileByName("foo.proto");
+  ASSERT_TRUE(file != nullptr);
+  const Descriptor* foo = pool.FindMessageTypeByName("Foo");
+  ASSERT_TRUE(foo != nullptr);
+  const EnumDescriptor* test_enum = pool.FindEnumTypeByName("TestEnum");
+  ASSERT_TRUE(test_enum != nullptr);
+  const ServiceDescriptor* test_service = pool.FindServiceByName("TestService");
+  ASSERT_TRUE(test_service != nullptr);
+
+  EXPECT_NE(0, call_counter.call_count_);
+  call_counter.Clear();
+
+  EXPECT_TRUE(foo->FindFieldByName("no_such_field") == nullptr);
+  EXPECT_TRUE(foo->FindExtensionByName("no_such_extension") == nullptr);
+  EXPECT_TRUE(foo->FindNestedTypeByName("NoSuchMessageType") == nullptr);
+  EXPECT_TRUE(foo->FindEnumTypeByName("NoSuchEnumType") == nullptr);
+  EXPECT_TRUE(foo->FindEnumValueByName("NO_SUCH_VALUE") == nullptr);
+  EXPECT_TRUE(test_enum->FindValueByName("NO_SUCH_VALUE") == nullptr);
+  EXPECT_TRUE(test_service->FindMethodByName("NoSuchMethod") == nullptr);
+
+  EXPECT_TRUE(file->FindMessageTypeByName("NoSuchMessageType") == nullptr);
+  EXPECT_TRUE(file->FindEnumTypeByName("NoSuchEnumType") == nullptr);
+  EXPECT_TRUE(file->FindEnumValueByName("NO_SUCH_VALUE") == nullptr);
+  EXPECT_TRUE(file->FindServiceByName("NO_SUCH_VALUE") == nullptr);
+  EXPECT_TRUE(file->FindExtensionByName("no_such_extension") == nullptr);
+
+  EXPECT_TRUE(pool.FindFileContainingSymbol("Foo.no.such.field") == nullptr);
+  EXPECT_TRUE(pool.FindFileContainingSymbol("Foo.no_such_field") == nullptr);
+  EXPECT_TRUE(pool.FindMessageTypeByName("Foo.NoSuchMessageType") == nullptr);
+  EXPECT_TRUE(pool.FindFieldByName("Foo.no_such_field") == nullptr);
+  EXPECT_TRUE(pool.FindExtensionByName("Foo.no_such_extension") == nullptr);
+  EXPECT_TRUE(pool.FindEnumTypeByName("Foo.NoSuchEnumType") == nullptr);
+  EXPECT_TRUE(pool.FindEnumValueByName("Foo.NO_SUCH_VALUE") == nullptr);
+  EXPECT_TRUE(pool.FindMethodByName("TestService.NoSuchMethod") == nullptr);
+
+  EXPECT_EQ(0, call_counter.call_count_);
+}
+
+TEST_F(DatabaseBackedPoolTest, DoesntReloadFilesUncesessarily) {
+  // If FindFileContainingSymbol() or FindFileContainingExtension() return a
+  // file that is already in the DescriptorPool, it should not attempt to
+  // reload the file.
+  FalsePositiveDatabase false_positive_database(&database_);
+  MockErrorCollector error_collector;
+  DescriptorPool pool(&false_positive_database, &error_collector);
+
+  // First make sure foo.proto is loaded.
+  const Descriptor* foo = pool.FindMessageTypeByName("Foo");
+  ASSERT_TRUE(foo != nullptr);
+
+  // Try inducing false positives.
+  EXPECT_TRUE(pool.FindMessageTypeByName("NoSuchSymbol") == nullptr);
+  EXPECT_TRUE(pool.FindExtensionByNumber(foo, 22) == nullptr);
+
+  // No errors should have been reported.  (If foo.proto was incorrectly
+  // loaded multiple times, errors would have been reported.)
+  EXPECT_EQ("", error_collector.text_);
+}
+
+// DescriptorDatabase that attempts to induce exponentially-bad performance
+// in DescriptorPool. For every positive N, the database contains a file
+// fileN.proto, which defines a message MessageN, which contains fields of
+// type MessageK for all K in [0,N). Message0 is not defined anywhere
+// (file0.proto exists, but is empty), so every other file and message type
+// will fail to build.
+//
+// If the DescriptorPool is not careful to memoize errors, an attempt to
+// build a descriptor for MessageN can require O(2^N) time.
+class ExponentialErrorDatabase : public DescriptorDatabase {
+ public:
+  ExponentialErrorDatabase() {}
+  ~ExponentialErrorDatabase() {}
+
+  // implements DescriptorDatabase ---------------------------------
+  bool FindFileByName(const std::string& filename,
+                      FileDescriptorProto* output) override {
+    int file_num = -1;
+    FullMatch(filename, "file", ".proto", &file_num);
+    if (file_num > -1) {
+      return PopulateFile(file_num, output);
+    } else {
+      return false;
+    }
+  }
+  bool FindFileContainingSymbol(const std::string& symbol_name,
+                                FileDescriptorProto* output) override {
+    int file_num = -1;
+    FullMatch(symbol_name, "Message", "", &file_num);
+    if (file_num > 0) {
+      return PopulateFile(file_num, output);
+    } else {
+      return false;
+    }
+  }
+  bool FindFileContainingExtension(const std::string& containing_type,
+                                   int field_number,
+                                   FileDescriptorProto* output) override {
+    return false;
+  }
+
+ private:
+  void FullMatch(const std::string& name, const std::string& begin_with,
+                 const std::string& end_with, int* file_num) {
+    int begin_size = begin_with.size();
+    int end_size = end_with.size();
+    if (name.substr(0, begin_size) != begin_with ||
+        name.substr(name.size() - end_size, end_size) != end_with) {
+      return;
+    }
+    safe_strto32(
+        name.substr(begin_size, name.size() - end_size - begin_size), file_num);
+  }
+
+  bool PopulateFile(int file_num, FileDescriptorProto* output) {
+    GOOGLE_CHECK_GE(file_num, 0);
+    output->Clear();
+    output->set_name(strings::Substitute("file$0.proto", file_num));
+    // file0.proto doesn't define Message0
+    if (file_num > 0) {
+      DescriptorProto* message = output->add_message_type();
+      message->set_name(strings::Substitute("Message$0", file_num));
+      for (int i = 0; i < file_num; ++i) {
+        output->add_dependency(strings::Substitute("file$0.proto", i));
+        FieldDescriptorProto* field = message->add_field();
+        field->set_name(strings::Substitute("field$0", i));
+        field->set_number(i);
+        field->set_label(FieldDescriptorProto::LABEL_OPTIONAL);
+        field->set_type(FieldDescriptorProto::TYPE_MESSAGE);
+        field->set_type_name(strings::Substitute("Message$0", i));
+      }
+    }
+    return true;
+  }
+};
+
+TEST_F(DatabaseBackedPoolTest, DoesntReloadKnownBadFiles) {
+  ExponentialErrorDatabase error_database;
+  DescriptorPool pool(&error_database);
+
+  GOOGLE_LOG(INFO) << "A timeout in this test probably indicates a real bug.";
+
+  EXPECT_TRUE(pool.FindFileByName("file40.proto") == nullptr);
+  EXPECT_TRUE(pool.FindMessageTypeByName("Message40") == nullptr);
+}
+
+TEST_F(DatabaseBackedPoolTest, DoesntFallbackOnWrongType) {
+  // If a lookup finds a symbol of the wrong type (e.g. we pass a type name
+  // to FindFieldByName()), we should fail fast, without checking the fallback
+  // database.
+  CallCountingDatabase call_counter(&database_);
+  DescriptorPool pool(&call_counter);
+
+  const FileDescriptor* file = pool.FindFileByName("foo.proto");
+  ASSERT_TRUE(file != nullptr);
+  const Descriptor* foo = pool.FindMessageTypeByName("Foo");
+  ASSERT_TRUE(foo != nullptr);
+  const EnumDescriptor* test_enum = pool.FindEnumTypeByName("TestEnum");
+  ASSERT_TRUE(test_enum != nullptr);
+
+  EXPECT_NE(0, call_counter.call_count_);
+  call_counter.Clear();
+
+  EXPECT_TRUE(pool.FindMessageTypeByName("TestEnum") == nullptr);
+  EXPECT_TRUE(pool.FindFieldByName("Foo") == nullptr);
+  EXPECT_TRUE(pool.FindExtensionByName("Foo") == nullptr);
+  EXPECT_TRUE(pool.FindEnumTypeByName("Foo") == nullptr);
+  EXPECT_TRUE(pool.FindEnumValueByName("Foo") == nullptr);
+  EXPECT_TRUE(pool.FindServiceByName("Foo") == nullptr);
+  EXPECT_TRUE(pool.FindMethodByName("Foo") == nullptr);
+
+  EXPECT_EQ(0, call_counter.call_count_);
+}
+
+// ===================================================================
+
+class AbortingErrorCollector : public DescriptorPool::ErrorCollector {
+ public:
+  AbortingErrorCollector() {}
+
+  void AddError(const std::string& filename, const std::string& element_name,
+                const Message* message, ErrorLocation location,
+                const std::string& error_message) override {
+    GOOGLE_LOG(FATAL) << "AddError() called unexpectedly: " << filename << " ["
+               << element_name << "]: " << error_message;
+  }
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(AbortingErrorCollector);
+};
+
+// A source tree containing only one file.
+class SingletonSourceTree : public compiler::SourceTree {
+ public:
+  SingletonSourceTree(const std::string& filename, const std::string& contents)
+      : filename_(filename), contents_(contents) {}
+
+  io::ZeroCopyInputStream* Open(const std::string& filename) override {
+    return filename == filename_
+               ? new io::ArrayInputStream(contents_.data(), contents_.size())
+               : nullptr;
+  }
+
+ private:
+  const std::string filename_;
+  const std::string contents_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(SingletonSourceTree);
+};
+
+const char* const kSourceLocationTestInput =
+    "syntax = \"proto2\";\n"
+    "option java_package = \"com.foo.bar\";\n"
+    "option (test_file_opt) = \"foobar\";\n"
+    "message A {\n"
+    "  option (test_msg_opt) = \"foobar\";\n"
+    "  optional int32 a = 1 [deprecated = true];\n"
+    "  message B {\n"
+    "    required double b = 1 [(test_field_opt) = \"foobar\"];\n"
+    "  }\n"
+    "  oneof c {\n"
+    "    option (test_oneof_opt) = \"foobar\";\n"
+    "    string d = 2;\n"
+    "    string e = 3;\n"
+    "    string f = 4;\n"
+    "  }\n"
+    "}\n"
+    "enum Indecision {\n"
+    "  option (test_enum_opt) = 21;\n"
+    "  option (test_enum_opt) = 42;\n"
+    "  option (test_enum_opt) = 63;\n"
+    "  YES   = 1 [(test_enumval_opt).a = 100];\n"
+    "  NO    = 2 [(test_enumval_opt) = {a:200}];\n"
+    "  MAYBE = 3;\n"
+    "}\n"
+    "service S {\n"
+    "  option (test_svc_opt) = {a:100};\n"
+    "  option (test_svc_opt) = {a:200};\n"
+    "  option (test_svc_opt) = {a:300};\n"
+    "  rpc Method(A) returns (A.B);\n"
+    // Put an empty line here to make the source location range match.
+    "\n"
+    "  rpc OtherMethod(A) returns (A) {\n"
+    "    option deprecated = true;\n"
+    "    option (test_method_opt) = \"foobar\";\n"
+    "  }\n"
+    "}\n"
+    "message MessageWithExtensions {\n"
+    "  extensions 1000 to 2000, 2001 to max [(test_ext_opt) = \"foobar\"];\n"
+    "}\n"
+    "extend MessageWithExtensions {\n"
+    "  repeated int32 int32_extension = 1001 [packed=true];\n"
+    "}\n"
+    "message C {\n"
+    "  extend MessageWithExtensions {\n"
+    "    optional C message_extension = 1002;\n"
+    "  }\n"
+    "}\n"
+    "import \"google/protobuf/descriptor.proto\";\n"
+    "extend google.protobuf.FileOptions {\n"
+    "  optional string test_file_opt = 10101;\n"
+    "}\n"
+    "extend google.protobuf.MessageOptions {\n"
+    "  optional string test_msg_opt = 10101;\n"
+    "}\n"
+    "extend google.protobuf.FieldOptions {\n"
+    "  optional string test_field_opt = 10101;\n"
+    "}\n"
+    "extend google.protobuf.EnumOptions {\n"
+    "  repeated int32 test_enum_opt = 10101;\n"
+    "}\n"
+    "extend google.protobuf.EnumValueOptions {\n"
+    "  optional A test_enumval_opt = 10101;\n"
+    "}\n"
+    "extend google.protobuf.ServiceOptions {\n"
+    "  repeated A test_svc_opt = 10101;\n"
+    "}\n"
+    "extend google.protobuf.MethodOptions {\n"
+    "  optional string test_method_opt = 10101;\n"
+    "}\n"
+    "extend google.protobuf.OneofOptions {\n"
+    "  optional string test_oneof_opt = 10101;\n"
+    "}\n"
+    "extend google.protobuf.ExtensionRangeOptions {\n"
+    "  optional string test_ext_opt = 10101;\n"
+    "}\n";
+
+class SourceLocationTest : public testing::Test {
+ public:
+  SourceLocationTest()
+      : source_tree_("/test/test.proto", kSourceLocationTestInput),
+        simple_db_(),
+        source_tree_db_(&source_tree_),
+        merged_db_(&simple_db_, &source_tree_db_),
+        pool_(&merged_db_, &collector_) {
+    // we need descriptor.proto to be accessible by the pool
+    // since our test file imports it
+    FileDescriptorProto::descriptor()->file()->CopyTo(&file_proto_);
+    simple_db_.Add(file_proto_);
+  }
+
+  static std::string PrintSourceLocation(const SourceLocation& loc) {
+    return strings::Substitute("$0:$1-$2:$3", 1 + loc.start_line,
+                            1 + loc.start_column, 1 + loc.end_line,
+                            1 + loc.end_column);
+  }
+
+ private:
+  FileDescriptorProto file_proto_;
+  AbortingErrorCollector collector_;
+  SingletonSourceTree source_tree_;
+  SimpleDescriptorDatabase simple_db_;  // contains descriptor.proto
+  compiler::SourceTreeDescriptorDatabase source_tree_db_;  // loads test.proto
+  MergedDescriptorDatabase merged_db_;  // combines above two dbs
+
+ protected:
+  DescriptorPool pool_;
+
+  // tag number of all custom options in above test file
+  static constexpr int kCustomOptionFieldNumber = 10101;
+  // tag number of field "a" in message type "A" in above test file
+  static constexpr int kAFieldNumber = 1;
+};
+
+// TODO(adonovan): implement support for option fields and for
+// subparts of declarations.
+
+TEST_F(SourceLocationTest, GetSourceLocation) {
+  SourceLocation loc;
+
+  const FileDescriptor* file_desc =
+      GOOGLE_CHECK_NOTNULL(pool_.FindFileByName("/test/test.proto"));
+
+  const Descriptor* a_desc = file_desc->FindMessageTypeByName("A");
+  EXPECT_TRUE(a_desc->GetSourceLocation(&loc));
+  EXPECT_EQ("4:1-16:2", PrintSourceLocation(loc));
+
+  const Descriptor* a_b_desc = a_desc->FindNestedTypeByName("B");
+  EXPECT_TRUE(a_b_desc->GetSourceLocation(&loc));
+  EXPECT_EQ("7:3-9:4", PrintSourceLocation(loc));
+
+  const EnumDescriptor* e_desc = file_desc->FindEnumTypeByName("Indecision");
+  EXPECT_TRUE(e_desc->GetSourceLocation(&loc));
+  EXPECT_EQ("17:1-24:2", PrintSourceLocation(loc));
+
+  const EnumValueDescriptor* yes_desc = e_desc->FindValueByName("YES");
+  EXPECT_TRUE(yes_desc->GetSourceLocation(&loc));
+  EXPECT_EQ("21:3-21:42", PrintSourceLocation(loc));
+
+  const ServiceDescriptor* s_desc = file_desc->FindServiceByName("S");
+  EXPECT_TRUE(s_desc->GetSourceLocation(&loc));
+  EXPECT_EQ("25:1-35:2", PrintSourceLocation(loc));
+
+  const MethodDescriptor* m_desc = s_desc->FindMethodByName("Method");
+  EXPECT_TRUE(m_desc->GetSourceLocation(&loc));
+  EXPECT_EQ("29:3-29:31", PrintSourceLocation(loc));
+
+}
+
+TEST_F(SourceLocationTest, ExtensionSourceLocation) {
+  SourceLocation loc;
+
+  const FileDescriptor* file_desc =
+      GOOGLE_CHECK_NOTNULL(pool_.FindFileByName("/test/test.proto"));
+
+  const FieldDescriptor* int32_extension_desc =
+      file_desc->FindExtensionByName("int32_extension");
+  EXPECT_TRUE(int32_extension_desc->GetSourceLocation(&loc));
+  EXPECT_EQ("40:3-40:55", PrintSourceLocation(loc));
+
+  const Descriptor* c_desc = file_desc->FindMessageTypeByName("C");
+  EXPECT_TRUE(c_desc->GetSourceLocation(&loc));
+  EXPECT_EQ("42:1-46:2", PrintSourceLocation(loc));
+
+  const FieldDescriptor* message_extension_desc =
+      c_desc->FindExtensionByName("message_extension");
+  EXPECT_TRUE(message_extension_desc->GetSourceLocation(&loc));
+  EXPECT_EQ("44:5-44:41", PrintSourceLocation(loc));
+}
+TEST_F(SourceLocationTest, InterpretedOptionSourceLocation) {
+  // This one's a doozy. It checks every kind of option, including
+  // extension range options.
+
+  // We are verifying that the file's source info contains correct
+  // info for interpreted options and that it does *not* contain
+  // any info for corresponding uninterpreted option path.
+
+  SourceLocation loc;
+
+  const FileDescriptor* file_desc =
+      GOOGLE_CHECK_NOTNULL(pool_.FindFileByName("/test/test.proto"));
+
+  // File options
+  {
+    int path[] = {FileDescriptorProto::kOptionsFieldNumber,
+                  FileOptions::kJavaPackageFieldNumber};
+    int unint[] = {FileDescriptorProto::kOptionsFieldNumber,
+                   FileOptions::kUninterpretedOptionFieldNumber, 0};
+
+    std::vector<int> vpath(path, path + 2);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("2:1-2:37", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 3);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+  {
+    int path[] = {FileDescriptorProto::kOptionsFieldNumber,
+                  kCustomOptionFieldNumber};
+    int unint[] = {FileDescriptorProto::kOptionsFieldNumber,
+                   FileOptions::kUninterpretedOptionFieldNumber, 1};
+    std::vector<int> vpath(path, path + 2);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("3:1-3:35", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 3);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+
+  // Message option
+  {
+    int path[] = {FileDescriptorProto::kMessageTypeFieldNumber, 0,
+                  DescriptorProto::kOptionsFieldNumber,
+                  kCustomOptionFieldNumber};
+    int unint[] = {FileDescriptorProto::kMessageTypeFieldNumber, 0,
+                   DescriptorProto::kOptionsFieldNumber,
+                   MessageOptions::kUninterpretedOptionFieldNumber, 0};
+    std::vector<int> vpath(path, path + 4);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("5:3-5:36", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 5);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+
+  // Field option
+  {
+    int path[] = {FileDescriptorProto::kMessageTypeFieldNumber,
+                  0,
+                  DescriptorProto::kFieldFieldNumber,
+                  0,
+                  FieldDescriptorProto::kOptionsFieldNumber,
+                  FieldOptions::kDeprecatedFieldNumber};
+    int unint[] = {FileDescriptorProto::kMessageTypeFieldNumber,
+                   0,
+                   DescriptorProto::kFieldFieldNumber,
+                   0,
+                   FieldDescriptorProto::kOptionsFieldNumber,
+                   FieldOptions::kUninterpretedOptionFieldNumber,
+                   0};
+    std::vector<int> vpath(path, path + 6);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("6:25-6:42", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 7);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+
+  // Nested message option
+  {
+    int path[] = {
+        FileDescriptorProto::kMessageTypeFieldNumber, 0,
+        DescriptorProto::kNestedTypeFieldNumber,      0,
+        DescriptorProto::kFieldFieldNumber,           0,
+        FieldDescriptorProto::kOptionsFieldNumber,    kCustomOptionFieldNumber};
+    int unint[] = {FileDescriptorProto::kMessageTypeFieldNumber,
+                   0,
+                   DescriptorProto::kNestedTypeFieldNumber,
+                   0,
+                   DescriptorProto::kFieldFieldNumber,
+                   0,
+                   FieldDescriptorProto::kOptionsFieldNumber,
+                   FieldOptions::kUninterpretedOptionFieldNumber,
+                   0};
+    std::vector<int> vpath(path, path + 8);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("8:28-8:55", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 9);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+
+  // One-of option
+  {
+    int path[] = {
+        FileDescriptorProto::kMessageTypeFieldNumber, 0,
+        DescriptorProto::kOneofDeclFieldNumber,       0,
+        OneofDescriptorProto::kOptionsFieldNumber,    kCustomOptionFieldNumber};
+    int unint[] = {FileDescriptorProto::kMessageTypeFieldNumber,
+                   0,
+                   DescriptorProto::kOneofDeclFieldNumber,
+                   0,
+                   OneofDescriptorProto::kOptionsFieldNumber,
+                   OneofOptions::kUninterpretedOptionFieldNumber,
+                   0};
+    std::vector<int> vpath(path, path + 6);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("11:5-11:40", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 7);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+
+  // Enum option, repeated options
+  {
+    int path[] = {FileDescriptorProto::kEnumTypeFieldNumber, 0,
+                  EnumDescriptorProto::kOptionsFieldNumber,
+                  kCustomOptionFieldNumber, 0};
+    int unint[] = {FileDescriptorProto::kEnumTypeFieldNumber, 0,
+                   EnumDescriptorProto::kOptionsFieldNumber,
+                   EnumOptions::kUninterpretedOptionFieldNumber, 0};
+    std::vector<int> vpath(path, path + 5);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("18:3-18:31", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 5);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+  {
+    int path[] = {FileDescriptorProto::kEnumTypeFieldNumber, 0,
+                  EnumDescriptorProto::kOptionsFieldNumber,
+                  kCustomOptionFieldNumber, 1};
+    int unint[] = {FileDescriptorProto::kEnumTypeFieldNumber, 0,
+                   EnumDescriptorProto::kOptionsFieldNumber,
+                   EnumOptions::kUninterpretedOptionFieldNumber, 1};
+    std::vector<int> vpath(path, path + 5);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("19:3-19:31", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 5);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+  {
+    int path[] = {FileDescriptorProto::kEnumTypeFieldNumber, 0,
+                  EnumDescriptorProto::kOptionsFieldNumber,
+                  kCustomOptionFieldNumber, 2};
+    int unint[] = {FileDescriptorProto::kEnumTypeFieldNumber, 0,
+                   EnumDescriptorProto::kOptionsFieldNumber,
+                   OneofOptions::kUninterpretedOptionFieldNumber, 2};
+    std::vector<int> vpath(path, path + 5);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("20:3-20:31", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 5);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+
+  // Enum value options
+  {
+    // option w/ message type that directly sets field
+    int path[] = {FileDescriptorProto::kEnumTypeFieldNumber,
+                  0,
+                  EnumDescriptorProto::kValueFieldNumber,
+                  0,
+                  EnumValueDescriptorProto::kOptionsFieldNumber,
+                  kCustomOptionFieldNumber,
+                  kAFieldNumber};
+    int unint[] = {FileDescriptorProto::kEnumTypeFieldNumber,
+                   0,
+                   EnumDescriptorProto::kValueFieldNumber,
+                   0,
+                   EnumValueDescriptorProto::kOptionsFieldNumber,
+                   EnumValueOptions::kUninterpretedOptionFieldNumber,
+                   0};
+    std::vector<int> vpath(path, path + 7);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("21:14-21:40", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 7);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+  {
+    int path[] = {FileDescriptorProto::kEnumTypeFieldNumber,
+                  0,
+                  EnumDescriptorProto::kValueFieldNumber,
+                  1,
+                  EnumValueDescriptorProto::kOptionsFieldNumber,
+                  kCustomOptionFieldNumber};
+    int unint[] = {FileDescriptorProto::kEnumTypeFieldNumber,
+                   0,
+                   EnumDescriptorProto::kValueFieldNumber,
+                   1,
+                   EnumValueDescriptorProto::kOptionsFieldNumber,
+                   EnumValueOptions::kUninterpretedOptionFieldNumber,
+                   0};
+    std::vector<int> vpath(path, path + 6);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("22:14-22:42", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 7);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+
+  // Service option, repeated options
+  {
+    int path[] = {FileDescriptorProto::kServiceFieldNumber, 0,
+                  ServiceDescriptorProto::kOptionsFieldNumber,
+                  kCustomOptionFieldNumber, 0};
+    int unint[] = {FileDescriptorProto::kServiceFieldNumber, 0,
+                   ServiceDescriptorProto::kOptionsFieldNumber,
+                   ServiceOptions::kUninterpretedOptionFieldNumber, 0};
+    std::vector<int> vpath(path, path + 5);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("26:3-26:35", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 5);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+  {
+    int path[] = {FileDescriptorProto::kServiceFieldNumber, 0,
+                  ServiceDescriptorProto::kOptionsFieldNumber,
+                  kCustomOptionFieldNumber, 1};
+    int unint[] = {FileDescriptorProto::kServiceFieldNumber, 0,
+                   ServiceDescriptorProto::kOptionsFieldNumber,
+                   ServiceOptions::kUninterpretedOptionFieldNumber, 1};
+    std::vector<int> vpath(path, path + 5);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("27:3-27:35", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 5);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+  {
+    int path[] = {FileDescriptorProto::kServiceFieldNumber, 0,
+                  ServiceDescriptorProto::kOptionsFieldNumber,
+                  kCustomOptionFieldNumber, 2};
+    int unint[] = {FileDescriptorProto::kServiceFieldNumber, 0,
+                   ServiceDescriptorProto::kOptionsFieldNumber,
+                   ServiceOptions::kUninterpretedOptionFieldNumber, 2};
+    std::vector<int> vpath(path, path + 5);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("28:3-28:35", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 5);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+
+  // Method options
+  {
+    int path[] = {FileDescriptorProto::kServiceFieldNumber,
+                  0,
+                  ServiceDescriptorProto::kMethodFieldNumber,
+                  1,
+                  MethodDescriptorProto::kOptionsFieldNumber,
+                  MethodOptions::kDeprecatedFieldNumber};
+    int unint[] = {FileDescriptorProto::kServiceFieldNumber,
+                   0,
+                   ServiceDescriptorProto::kMethodFieldNumber,
+                   1,
+                   MethodDescriptorProto::kOptionsFieldNumber,
+                   MethodOptions::kUninterpretedOptionFieldNumber,
+                   0};
+    std::vector<int> vpath(path, path + 6);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("32:5-32:30", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 7);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+  {
+    int path[] = {
+        FileDescriptorProto::kServiceFieldNumber,   0,
+        ServiceDescriptorProto::kMethodFieldNumber, 1,
+        MethodDescriptorProto::kOptionsFieldNumber, kCustomOptionFieldNumber};
+    int unint[] = {FileDescriptorProto::kServiceFieldNumber,
+                   0,
+                   ServiceDescriptorProto::kMethodFieldNumber,
+                   1,
+                   MethodDescriptorProto::kOptionsFieldNumber,
+                   MethodOptions::kUninterpretedOptionFieldNumber,
+                   1};
+    std::vector<int> vpath(path, path + 6);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("33:5-33:41", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 7);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+
+  // Extension range options
+  {
+    int path[] = {FileDescriptorProto::kMessageTypeFieldNumber, 1,
+                  DescriptorProto::kExtensionRangeFieldNumber, 0,
+                  DescriptorProto_ExtensionRange::kOptionsFieldNumber};
+    std::vector<int> vpath(path, path + 5);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("37:40-37:67", PrintSourceLocation(loc));
+  }
+  {
+    int path[] = {FileDescriptorProto::kMessageTypeFieldNumber,
+                  1,
+                  DescriptorProto::kExtensionRangeFieldNumber,
+                  0,
+                  DescriptorProto_ExtensionRange::kOptionsFieldNumber,
+                  kCustomOptionFieldNumber};
+    int unint[] = {FileDescriptorProto::kMessageTypeFieldNumber,
+                   1,
+                   DescriptorProto::kExtensionRangeFieldNumber,
+                   0,
+                   DescriptorProto_ExtensionRange::kOptionsFieldNumber,
+                   ExtensionRangeOptions::kUninterpretedOptionFieldNumber,
+                   0};
+    std::vector<int> vpath(path, path + 6);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("37:41-37:66", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 7);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+  {
+    int path[] = {FileDescriptorProto::kMessageTypeFieldNumber,
+                  1,
+                  DescriptorProto::kExtensionRangeFieldNumber,
+                  1,
+                  DescriptorProto_ExtensionRange::kOptionsFieldNumber,
+                  kCustomOptionFieldNumber};
+    int unint[] = {FileDescriptorProto::kMessageTypeFieldNumber,
+                   1,
+                   DescriptorProto::kExtensionRangeFieldNumber,
+                   1,
+                   DescriptorProto_ExtensionRange::kOptionsFieldNumber,
+                   ExtensionRangeOptions::kUninterpretedOptionFieldNumber,
+                   0};
+    std::vector<int> vpath(path, path + 6);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("37:41-37:66", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 7);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+
+  // Field option on extension
+  {
+    int path[] = {FileDescriptorProto::kExtensionFieldNumber, 0,
+                  FieldDescriptorProto::kOptionsFieldNumber,
+                  FieldOptions::kPackedFieldNumber};
+    int unint[] = {FileDescriptorProto::kExtensionFieldNumber, 0,
+                   FieldDescriptorProto::kOptionsFieldNumber,
+                   FieldOptions::kUninterpretedOptionFieldNumber, 0};
+    std::vector<int> vpath(path, path + 4);
+    EXPECT_TRUE(file_desc->GetSourceLocation(vpath, &loc));
+    EXPECT_EQ("40:42-40:53", PrintSourceLocation(loc));
+
+    std::vector<int> vunint(unint, unint + 5);
+    EXPECT_FALSE(file_desc->GetSourceLocation(vunint, &loc));
+  }
+}
+
+// Missing SourceCodeInfo doesn't cause crash:
+TEST_F(SourceLocationTest, GetSourceLocation_MissingSourceCodeInfo) {
+  SourceLocation loc;
+
+  const FileDescriptor* file_desc =
+      GOOGLE_CHECK_NOTNULL(pool_.FindFileByName("/test/test.proto"));
+
+  FileDescriptorProto proto;
+  file_desc->CopyTo(&proto);  // Note, this discards the SourceCodeInfo.
+  EXPECT_FALSE(proto.has_source_code_info());
+
+  DescriptorPool bad1_pool(&pool_);
+  const FileDescriptor* bad1_file_desc =
+      GOOGLE_CHECK_NOTNULL(bad1_pool.BuildFile(proto));
+  const Descriptor* bad1_a_desc = bad1_file_desc->FindMessageTypeByName("A");
+  EXPECT_FALSE(bad1_a_desc->GetSourceLocation(&loc));
+}
+
+// Corrupt SourceCodeInfo doesn't cause crash:
+TEST_F(SourceLocationTest, GetSourceLocation_BogusSourceCodeInfo) {
+  SourceLocation loc;
+
+  const FileDescriptor* file_desc =
+      GOOGLE_CHECK_NOTNULL(pool_.FindFileByName("/test/test.proto"));
+
+  FileDescriptorProto proto;
+  file_desc->CopyTo(&proto);  // Note, this discards the SourceCodeInfo.
+  EXPECT_FALSE(proto.has_source_code_info());
+  SourceCodeInfo_Location* loc_msg =
+      proto.mutable_source_code_info()->add_location();
+  loc_msg->add_path(1);
+  loc_msg->add_path(2);
+  loc_msg->add_path(3);
+  loc_msg->add_span(4);
+  loc_msg->add_span(5);
+  loc_msg->add_span(6);
+
+  DescriptorPool bad2_pool(&pool_);
+  const FileDescriptor* bad2_file_desc =
+      GOOGLE_CHECK_NOTNULL(bad2_pool.BuildFile(proto));
+  const Descriptor* bad2_a_desc = bad2_file_desc->FindMessageTypeByName("A");
+  EXPECT_FALSE(bad2_a_desc->GetSourceLocation(&loc));
+}
+
+// ===================================================================
+
+const char* const kCopySourceCodeInfoToTestInput =
+    "syntax = \"proto2\";\n"
+    "message Foo {}\n";
+
+// Required since source code information is not preserved by
+// FileDescriptorTest.
+class CopySourceCodeInfoToTest : public testing::Test {
+ public:
+  CopySourceCodeInfoToTest()
+      : source_tree_("/test/test.proto", kCopySourceCodeInfoToTestInput),
+        db_(&source_tree_),
+        pool_(&db_, &collector_) {}
+
+ private:
+  AbortingErrorCollector collector_;
+  SingletonSourceTree source_tree_;
+  compiler::SourceTreeDescriptorDatabase db_;
+
+ protected:
+  DescriptorPool pool_;
+};
+
+TEST_F(CopySourceCodeInfoToTest, CopyTo_DoesNotCopySourceCodeInfo) {
+  const FileDescriptor* file_desc =
+      GOOGLE_CHECK_NOTNULL(pool_.FindFileByName("/test/test.proto"));
+  FileDescriptorProto file_desc_proto;
+  ASSERT_FALSE(file_desc_proto.has_source_code_info());
+
+  file_desc->CopyTo(&file_desc_proto);
+  EXPECT_FALSE(file_desc_proto.has_source_code_info());
+}
+
+TEST_F(CopySourceCodeInfoToTest, CopySourceCodeInfoTo) {
+  const FileDescriptor* file_desc =
+      GOOGLE_CHECK_NOTNULL(pool_.FindFileByName("/test/test.proto"));
+  FileDescriptorProto file_desc_proto;
+  ASSERT_FALSE(file_desc_proto.has_source_code_info());
+
+  file_desc->CopySourceCodeInfoTo(&file_desc_proto);
+  const SourceCodeInfo& info = file_desc_proto.source_code_info();
+  ASSERT_EQ(4, info.location_size());
+  // Get the Foo message location
+  const SourceCodeInfo_Location& foo_location = info.location(2);
+  ASSERT_EQ(2, foo_location.path_size());
+  EXPECT_EQ(FileDescriptorProto::kMessageTypeFieldNumber, foo_location.path(0));
+  EXPECT_EQ(0, foo_location.path(1));      // Foo is the first message defined
+  ASSERT_EQ(3, foo_location.span_size());  // Foo spans one line
+  EXPECT_EQ(1, foo_location.span(0));      // Foo is declared on line 1
+  EXPECT_EQ(0, foo_location.span(1));      // Foo starts at column 0
+  EXPECT_EQ(14, foo_location.span(2));     // Foo ends on column 14
+}
+
+// ===================================================================
+
+class LazilyBuildDependenciesTest : public testing::Test {
+ public:
+  LazilyBuildDependenciesTest() : pool_(&db_, nullptr) {
+    pool_.InternalSetLazilyBuildDependencies();
+  }
+
+  void ParseProtoAndAddToDb(const char* proto) {
+    FileDescriptorProto tmp;
+    ASSERT_TRUE(TextFormat::ParseFromString(proto, &tmp));
+    db_.Add(tmp);
+  }
+
+  void ParseProtoAndAddToDb(const std::string& proto) {
+    FileDescriptorProto tmp;
+    ASSERT_TRUE(TextFormat::ParseFromString(proto, &tmp));
+    db_.Add(tmp);
+  }
+
+  void AddSimpleMessageProtoFileToDb(const char* file_name,
+                                     const char* message_name) {
+    ParseProtoAndAddToDb("name: '" + std::string(file_name) +
+                         ".proto' "
+                         "package: \"protobuf_unittest\" "
+                         "message_type { "
+                         "  name:'" +
+                         std::string(message_name) +
+                         "' "
+                         "  field { name:'a' number:1 "
+                         "  label:LABEL_OPTIONAL "
+                         "  type_name:'int32' } "
+                         "}");
+  }
+
+  void AddSimpleEnumProtoFileToDb(const char* file_name, const char* enum_name,
+                                  const char* enum_value_name) {
+    ParseProtoAndAddToDb("name: '" + std::string(file_name) +
+                         ".proto' "
+                         "package: 'protobuf_unittest' "
+                         "enum_type { "
+                         "  name:'" +
+                         std::string(enum_name) +
+                         "' "
+                         "  value { name:'" +
+                         std::string(enum_value_name) +
+                         "' number:1 } "
+                         "}");
+  }
+
+ protected:
+  SimpleDescriptorDatabase db_;
+  DescriptorPool pool_;
+};
+
+TEST_F(LazilyBuildDependenciesTest, Message) {
+  ParseProtoAndAddToDb(
+      "name: 'foo.proto' "
+      "package: 'protobuf_unittest' "
+      "dependency: 'bar.proto' "
+      "message_type { "
+      "  name:'Foo' "
+      "  field { name:'bar' number:1 label:LABEL_OPTIONAL "
+      "type_name:'.protobuf_unittest.Bar' } "
+      "}");
+  AddSimpleMessageProtoFileToDb("bar", "Bar");
+
+  // Verify neither has been built yet.
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("foo.proto"));
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("bar.proto"));
+
+  const FileDescriptor* file = pool_.FindFileByName("foo.proto");
+
+  // Verify only foo gets built when asking for foo.proto
+  EXPECT_TRUE(file != nullptr);
+  EXPECT_TRUE(pool_.InternalIsFileLoaded("foo.proto"));
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("bar.proto"));
+
+  // Verify calling FindFieldBy* works when the type of the field was
+  // not built at cross link time. Verify this doesn't build the file
+  // the field's type is defined in, as well.
+  const Descriptor* desc = file->FindMessageTypeByName("Foo");
+  const FieldDescriptor* field = desc->FindFieldByName("bar");
+  EXPECT_TRUE(field != nullptr);
+  EXPECT_EQ(field, desc->FindFieldByNumber(1));
+  EXPECT_EQ(field, desc->FindFieldByLowercaseName("bar"));
+  EXPECT_EQ(field, desc->FindFieldByCamelcaseName("bar"));
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("bar.proto"));
+
+  // Finally, verify that if we call message_type() on the field, we will
+  // build the file where the message is defined, and get a valid descriptor
+  EXPECT_TRUE(field->message_type() != nullptr);
+  EXPECT_TRUE(pool_.InternalIsFileLoaded("bar.proto"));
+}
+
+TEST_F(LazilyBuildDependenciesTest, Enum) {
+  ParseProtoAndAddToDb(
+      "name: 'foo.proto' "
+      "package: 'protobuf_unittest' "
+      "dependency: 'enum1.proto' "
+      "dependency: 'enum2.proto' "
+      "message_type { "
+      "  name:'Lazy' "
+      "  field { name:'enum1' number:1 label:LABEL_OPTIONAL "
+      "type_name:'.protobuf_unittest.Enum1' } "
+      "  field { name:'enum2' number:1 label:LABEL_OPTIONAL "
+      "type_name:'.protobuf_unittest.Enum2' } "
+      "}");
+  AddSimpleEnumProtoFileToDb("enum1", "Enum1", "ENUM1");
+  AddSimpleEnumProtoFileToDb("enum2", "Enum2", "ENUM2");
+
+  const FileDescriptor* file = pool_.FindFileByName("foo.proto");
+
+  // Verify calling enum_type() on a field whose definition is not
+  // yet built will build the file and return a descriptor.
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("enum1.proto"));
+  const Descriptor* desc = file->FindMessageTypeByName("Lazy");
+  EXPECT_TRUE(desc != nullptr);
+  const FieldDescriptor* field = desc->FindFieldByName("enum1");
+  EXPECT_TRUE(field != nullptr);
+  EXPECT_TRUE(field->enum_type() != nullptr);
+  EXPECT_TRUE(pool_.InternalIsFileLoaded("enum1.proto"));
+
+  // Verify calling default_value_enum() on a field whose definition is not
+  // yet built will build the file and return a descriptor to the value.
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("enum2.proto"));
+  field = desc->FindFieldByName("enum2");
+  EXPECT_TRUE(field != nullptr);
+  EXPECT_TRUE(field->default_value_enum() != nullptr);
+  EXPECT_TRUE(pool_.InternalIsFileLoaded("enum2.proto"));
+}
+
+TEST_F(LazilyBuildDependenciesTest, Type) {
+  ParseProtoAndAddToDb(
+      "name: 'foo.proto' "
+      "package: 'protobuf_unittest' "
+      "dependency: 'message1.proto' "
+      "dependency: 'message2.proto' "
+      "dependency: 'enum1.proto' "
+      "dependency: 'enum2.proto' "
+      "message_type { "
+      "  name:'Lazy' "
+      "  field { name:'message1' number:1 label:LABEL_OPTIONAL "
+      "type_name:'.protobuf_unittest.Message1' } "
+      "  field { name:'message2' number:1 label:LABEL_OPTIONAL "
+      "type_name:'.protobuf_unittest.Message2' } "
+      "  field { name:'enum1' number:1 label:LABEL_OPTIONAL "
+      "type_name:'.protobuf_unittest.Enum1' } "
+      "  field { name:'enum2' number:1 label:LABEL_OPTIONAL "
+      "type_name:'.protobuf_unittest.Enum2' } "
+      "}");
+  AddSimpleMessageProtoFileToDb("message1", "Message1");
+  AddSimpleMessageProtoFileToDb("message2", "Message2");
+  AddSimpleEnumProtoFileToDb("enum1", "Enum1", "ENUM1");
+  AddSimpleEnumProtoFileToDb("enum2", "Enum2", "ENUM2");
+
+  const FileDescriptor* file = pool_.FindFileByName("foo.proto");
+
+  // Verify calling type() on a field that is a message type will
+  // build the type defined in another file.
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("message1.proto"));
+  const Descriptor* desc = file->FindMessageTypeByName("Lazy");
+  EXPECT_TRUE(desc != nullptr);
+  const FieldDescriptor* field = desc->FindFieldByName("message1");
+  EXPECT_TRUE(field != nullptr);
+  EXPECT_EQ(field->type(), FieldDescriptor::TYPE_MESSAGE);
+  EXPECT_TRUE(pool_.InternalIsFileLoaded("message1.proto"));
+
+  // Verify calling cpp_type() on a field that is a message type will
+  // build the type defined in another file.
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("message2.proto"));
+  field = desc->FindFieldByName("message2");
+  EXPECT_TRUE(field != nullptr);
+  EXPECT_EQ(field->cpp_type(), FieldDescriptor::CPPTYPE_MESSAGE);
+  EXPECT_TRUE(pool_.InternalIsFileLoaded("message2.proto"));
+
+  // Verify calling type() on a field that is an enum type will
+  // build the type defined in another file.
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("enum1.proto"));
+  field = desc->FindFieldByName("enum1");
+  EXPECT_TRUE(field != nullptr);
+  EXPECT_EQ(field->type(), FieldDescriptor::TYPE_ENUM);
+  EXPECT_TRUE(pool_.InternalIsFileLoaded("enum1.proto"));
+
+  // Verify calling cpp_type() on a field that is an enum type will
+  // build the type defined in another file.
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("enum2.proto"));
+  field = desc->FindFieldByName("enum2");
+  EXPECT_TRUE(field != nullptr);
+  EXPECT_EQ(field->cpp_type(), FieldDescriptor::CPPTYPE_ENUM);
+  EXPECT_TRUE(pool_.InternalIsFileLoaded("enum2.proto"));
+}
+
+TEST_F(LazilyBuildDependenciesTest, Extension) {
+  ParseProtoAndAddToDb(
+      "name: 'foo.proto' "
+      "package: 'protobuf_unittest' "
+      "dependency: 'bar.proto' "
+      "dependency: 'baz.proto' "
+      "extension { extendee: '.protobuf_unittest.Bar' name:'bar' number:11"
+      "            label:LABEL_OPTIONAL type_name:'.protobuf_unittest.Baz' }");
+  ParseProtoAndAddToDb(
+      "name: 'bar.proto' "
+      "package: 'protobuf_unittest' "
+      "message_type { "
+      "  name:'Bar' "
+      "  extension_range { start: 10 end: 20 }"
+      "}");
+  AddSimpleMessageProtoFileToDb("baz", "Baz");
+
+  // Verify none have been built yet.
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("foo.proto"));
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("bar.proto"));
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("baz.proto"));
+
+  const FileDescriptor* file = pool_.FindFileByName("foo.proto");
+
+  // Verify foo.bar gets loaded, and bar.proto gets loaded
+  // to register the extension. baz.proto should not get loaded.
+  EXPECT_TRUE(file != nullptr);
+  EXPECT_TRUE(pool_.InternalIsFileLoaded("foo.proto"));
+  EXPECT_TRUE(pool_.InternalIsFileLoaded("bar.proto"));
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("baz.proto"));
+}
+
+TEST_F(LazilyBuildDependenciesTest, Service) {
+  ParseProtoAndAddToDb(
+      "name: 'foo.proto' "
+      "package: 'protobuf_unittest' "
+      "dependency: 'message1.proto' "
+      "dependency: 'message2.proto' "
+      "dependency: 'message3.proto' "
+      "dependency: 'message4.proto' "
+      "service {"
+      "  name: 'LazyService'"
+      "  method { name: 'A' input_type:  '.protobuf_unittest.Message1' "
+      "                     output_type: '.protobuf_unittest.Message2' }"
+      "}");
+  AddSimpleMessageProtoFileToDb("message1", "Message1");
+  AddSimpleMessageProtoFileToDb("message2", "Message2");
+  AddSimpleMessageProtoFileToDb("message3", "Message3");
+  AddSimpleMessageProtoFileToDb("message4", "Message4");
+
+  const FileDescriptor* file = pool_.FindFileByName("foo.proto");
+
+  // Verify calling FindServiceByName or FindMethodByName doesn't build the
+  // files defining the input and output type, and input_type() and
+  // output_type() does indeed build the appropriate files.
+  const ServiceDescriptor* service = file->FindServiceByName("LazyService");
+  EXPECT_TRUE(service != nullptr);
+  const MethodDescriptor* method = service->FindMethodByName("A");
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("message1.proto"));
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("message2.proto"));
+  EXPECT_TRUE(method != nullptr);
+  EXPECT_TRUE(method->input_type() != nullptr);
+  EXPECT_TRUE(pool_.InternalIsFileLoaded("message1.proto"));
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("message2.proto"));
+  EXPECT_TRUE(method->output_type() != nullptr);
+  EXPECT_TRUE(pool_.InternalIsFileLoaded("message2.proto"));
+}
+
+
+TEST_F(LazilyBuildDependenciesTest, GeneratedFile) {
+  // Most testing is done with custom pools with lazy dependencies forced on,
+  // do some sanity checking that lazy imports is on by default for the
+  // generated pool, and do custom options testing with generated to
+  // be able to use the GetExtension ids for the custom options.
+
+  // Verify none of the files are loaded yet.
+  EXPECT_FALSE(DescriptorPool::generated_pool()->InternalIsFileLoaded(
+      "google/protobuf/unittest_lazy_dependencies.proto"));
+  EXPECT_FALSE(DescriptorPool::generated_pool()->InternalIsFileLoaded(
+      "google/protobuf/unittest_lazy_dependencies_custom_option.proto"));
+  EXPECT_FALSE(DescriptorPool::generated_pool()->InternalIsFileLoaded(
+      "google/protobuf/unittest_lazy_dependencies_enum.proto"));
+
+  // Verify calling autogenerated function to get a descriptor in the base
+  // file will build that file but none of it's imports. This verifies that
+  // lazily_build_dependencies_ is set on the generated pool, and also that
+  // the generated function "descriptor()" doesn't somehow subvert the laziness
+  // by manually loading the dependencies or something.
+  EXPECT_TRUE(protobuf_unittest::lazy_imports::ImportedMessage::descriptor() !=
+              nullptr);
+  EXPECT_TRUE(DescriptorPool::generated_pool()->InternalIsFileLoaded(
+      "google/protobuf/unittest_lazy_dependencies.proto"));
+  EXPECT_FALSE(DescriptorPool::generated_pool()->InternalIsFileLoaded(
+      "google/protobuf/unittest_lazy_dependencies_custom_option.proto"));
+  EXPECT_FALSE(DescriptorPool::generated_pool()->InternalIsFileLoaded(
+      "google/protobuf/unittest_lazy_dependencies_enum.proto"));
+
+  // Verify custom options work when defined in an import that isn't loaded,
+  // and that a non-default value of a custom option doesn't load the file
+  // where that enum is defined.
+  const MessageOptions& options =
+      protobuf_unittest::lazy_imports::MessageCustomOption::descriptor()
+          ->options();
+  protobuf_unittest::lazy_imports::LazyEnum custom_option_value =
+      options.GetExtension(protobuf_unittest::lazy_imports::lazy_enum_option);
+
+  EXPECT_FALSE(DescriptorPool::generated_pool()->InternalIsFileLoaded(
+      "google/protobuf/unittest_lazy_dependencies_custom_option.proto"));
+  EXPECT_FALSE(DescriptorPool::generated_pool()->InternalIsFileLoaded(
+      "google/protobuf/unittest_lazy_dependencies_enum.proto"));
+  EXPECT_EQ(custom_option_value, protobuf_unittest::lazy_imports::LAZY_ENUM_1);
+
+  const MessageOptions& options2 =
+      protobuf_unittest::lazy_imports::MessageCustomOption2::descriptor()
+          ->options();
+  custom_option_value =
+      options2.GetExtension(protobuf_unittest::lazy_imports::lazy_enum_option);
+
+  EXPECT_FALSE(DescriptorPool::generated_pool()->InternalIsFileLoaded(
+      "google/protobuf/unittest_lazy_dependencies_custom_option.proto"));
+  EXPECT_FALSE(DescriptorPool::generated_pool()->InternalIsFileLoaded(
+      "google/protobuf/unittest_lazy_dependencies_enum.proto"));
+  EXPECT_EQ(custom_option_value, protobuf_unittest::lazy_imports::LAZY_ENUM_0);
+}
+
+TEST_F(LazilyBuildDependenciesTest, Dependency) {
+  ParseProtoAndAddToDb(
+      "name: 'foo.proto' "
+      "package: 'protobuf_unittest' "
+      "dependency: 'bar.proto' "
+      "message_type { "
+      "  name:'Foo' "
+      "  field { name:'bar' number:1 label:LABEL_OPTIONAL "
+      "type_name:'.protobuf_unittest.Bar' } "
+      "}");
+  ParseProtoAndAddToDb(
+      "name: 'bar.proto' "
+      "package: 'protobuf_unittest' "
+      "dependency: 'baz.proto' "
+      "message_type { "
+      "  name:'Bar' "
+      "  field { name:'baz' number:1 label:LABEL_OPTIONAL "
+      "type_name:'.protobuf_unittest.Baz' } "
+      "}");
+  AddSimpleMessageProtoFileToDb("baz", "Baz");
+
+  const FileDescriptor* foo_file = pool_.FindFileByName("foo.proto");
+  EXPECT_TRUE(foo_file != nullptr);
+  // As expected, requesting foo.proto shouldn't build it's dependencies
+  EXPECT_TRUE(pool_.InternalIsFileLoaded("foo.proto"));
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("bar.proto"));
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("baz.proto"));
+
+  // Verify calling dependency(N) will build the dependency, but
+  // not that file's dependencies.
+  const FileDescriptor* bar_file = foo_file->dependency(0);
+  EXPECT_TRUE(bar_file != nullptr);
+  EXPECT_TRUE(pool_.InternalIsFileLoaded("bar.proto"));
+  EXPECT_FALSE(pool_.InternalIsFileLoaded("baz.proto"));
+}
+
+// ===================================================================
+
+
+}  // namespace descriptor_unittest
+}  // namespace protobuf
+}  // namespace google
+
+#include <port_undef.inc>