zig build: reintroduce --prominent-compile-errors

This reintroduced flag makes zig build behave the same as the previous
commit. Without this flag, the default behavior is now changed to
display compilation errors inline with the rest of error messages and
the build tree context.

This behavior is essential for making sense of error logs from projects
that have two or more steps emitting compilation errors which is why it
is now the default.

2 files changed, 18 insertions, 3 deletions

diff --git a/lib/build_runner.zig b/lib/build_runner.zig
index 687a1eb151..979cc93f11 100644
--- a/lib/build_runner.zig
+++ b/lib/build_runner.zig
@@ -99,6 +99,7 @@ pub fn main() !void {
     var skip_oom_steps: bool = false;
     var color: Color = .auto;
     var seed: u32 = 0;
+    var prominent_compile_errors: bool = false;
 
     const stderr_stream = io.getStdErr().writer();
     const stdout_stream = io.getStdOut().writer();
@@ -242,6 +243,8 @@ pub fn main() !void {
                 builder.verbose_cc = true;
             } else if (mem.eql(u8, arg, "--verbose-llvm-cpu-features")) {
                 builder.verbose_llvm_cpu_features = true;
+            } else if (mem.eql(u8, arg, "--prominent-compile-errors")) {
+                prominent_compile_errors = true;
             } else if (mem.eql(u8, arg, "-fwine")) {
                 builder.enable_wine = true;
             } else if (mem.eql(u8, arg, "-fno-wine")) {
@@ -325,6 +328,7 @@ pub fn main() !void {
         .max_rss_mutex = .{},
         .skip_oom_steps = skip_oom_steps,
         .memory_blocked_steps = std.ArrayList(*Step).init(arena),
+        .prominent_compile_errors = prominent_compile_errors,
 
         .claimed_rss = 0,
         .summary = summary,
@@ -357,6 +361,7 @@ const Run = struct {
     max_rss_mutex: std.Thread.Mutex,
     skip_oom_steps: bool,
     memory_blocked_steps: std.ArrayList(*Step),
+    prominent_compile_errors: bool,
 
     claimed_rss: usize,
     summary: ?Summary,
@@ -561,7 +566,7 @@ fn runStepNames(
     // Finally, render compile errors at the bottom of the terminal.
     // We use a separate compile_error_steps array list because step_stack is destructively
     // mutated in printTreeStep above.
-    if (total_compile_errors > 0) {
+    if (run.prominent_compile_errors and total_compile_errors > 0) {
         for (compile_error_steps.items) |s| {
             if (s.result_error_bundle.errorMessageCount() > 0) {
                 s.result_error_bundle.renderToStdErr(renderOptions(ttyconf));
@@ -910,7 +915,11 @@ fn workerMakeOneStep(
     const make_result = s.make(&sub_prog_node);
 
     // No matter the result, we want to display error/warning messages.
-    if (s.result_error_msgs.items.len > 0) {
+    const show_compile_errors = !run.prominent_compile_errors and
+        s.result_error_bundle.errorMessageCount() > 0;
+    const show_error_msgs = s.result_error_msgs.items.len > 0;
+
+    if (show_error_msgs or show_compile_errors) {
         sub_prog_node.context.lock_stderr();
         defer sub_prog_node.context.unlock_stderr();
 
@@ -1003,7 +1012,11 @@ fn printErrorMessages(b: *std.Build, failing_step: *Step, run: *const Run) !void
     }
     try ttyconf.setColor(stderr, .reset);
 
-    // Finally, the actual error messages.
+    // Penultimately, the compilation errors.
+    if (!run.prominent_compile_errors and failing_step.result_error_bundle.errorMessageCount() > 0)
+        try failing_step.result_error_bundle.renderToWriter(renderOptions(ttyconf), stderr.writer());
+
+    // Finally, generic error messages.
     for (failing_step.result_error_msgs.items) |msg| {
         try ttyconf.setColor(stderr, .red);
         try stderr.writeAll("error: ");
@@ -1078,6 +1091,7 @@ fn usage(builder: *std.Build, already_ran_build: bool, out_stream: anytype) !voi
         \\  -l, --list-steps             Print available steps
         \\  --verbose                    Print commands before executing them
         \\  --color [auto|off|on]        Enable or disable colored error messages
+        \\  --prominent-compile-errors   Buffer compile errors and display at end
         \\  --summary [mode]             Control the printing of the build summary
         \\    all                        Print the build summary in its entirety
         \\    failures                   (Default) Only print failed steps
diff --git a/src/main.zig b/src/main.zig
index 54db7eb37d..a8ff0721ad 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -5096,6 +5096,7 @@ pub const usage_build =
     \\  --global-cache-dir [path]     Override path to global Zig cache directory
     \\  --zig-lib-dir [arg]           Override path to Zig lib directory
     \\  --build-runner [file]         Override path to build runner
+    \\  --prominent-compile-errors    Buffer compile errors and display at end
     \\  --seed [integer]              For shuffling dependency traversal order (default: random)
     \\  --fetch                       Exit after fetching dependency tree
     \\  -h, --help                    Print this help and exit