zig fmt: bypass auto indentation for `// zig fmt: on`

Currently an indented `// zig fmt: on` will be indented an additional
time on every run of zig fmt.

2 files changed, 23 insertions, 2 deletions

diff --git a/lib/std/zig/parser_test.zig b/lib/std/zig/parser_test.zig
index 1bed86f42d..c433ee5ad8 100644
--- a/lib/std/zig/parser_test.zig
+++ b/lib/std/zig/parser_test.zig
@@ -1315,6 +1315,27 @@ test "zig fmt: 'zig fmt: (off|on)' works in the middle of code" {
     );
 }
 
+test "zig fmt: 'zig fmt: on' indentation is unchanged" {
+    try testCanonical(
+        \\fn initOptionsAndLayouts(output: *Output, context: *Context) !void {
+        \\    // zig fmt: off
+        \\    try output.main_amount.init(output, "main_amount"); errdefer optput.main_amount.deinit();
+        \\    try output.main_factor.init(output, "main_factor"); errdefer optput.main_factor.deinit();
+        \\    try output.view_padding.init(output, "view_padding"); errdefer optput.view_padding.deinit();
+        \\    try output.outer_padding.init(output, "outer_padding"); errdefer optput.outer_padding.deinit();
+        \\    // zig fmt: on
+        \\
+        \\    // zig fmt: off
+        \\    try output.top.init(output, .top); errdefer optput.top.deinit();
+        \\    try output.right.init(output, .right); errdefer optput.right.deinit();
+        \\    try output.bottom.init(output, .bottom); errdefer optput.bottom.deinit();
+        \\    try output.left.init(output, .left); errdefer optput.left.deinit();
+        \\        // zig fmt: on
+        \\}
+        \\
+    );
+}
+
 test "zig fmt: pointer of unknown length" {
     try testCanonical(
         \\fn foo(ptr: [*]u8) void {}
diff --git a/lib/std/zig/render.zig b/lib/std/zig/render.zig
index 71d5e51bb9..9291f63e2f 100644
--- a/lib/std/zig/render.zig
+++ b/lib/std/zig/render.zig
@@ -2311,9 +2311,9 @@ fn renderComments(ais: *Ais, tree: ast.Tree, start: usize, end: usize) Error!boo
             // to the underlying writer, fixing up invaild whitespace.
             const disabled_source = tree.source[ais.disabled_offset.?..comment_start];
             try writeFixingWhitespace(ais.underlying_writer, disabled_source);
-            ais.disabled_offset = null;
             // Write with the canonical single space.
-            try ais.writer().writeAll("// zig fmt: on\n");
+            try ais.underlying_writer.writeAll("// zig fmt: on\n");
+            ais.disabled_offset = null;
         } else if (ais.disabled_offset == null and mem.eql(u8, comment_content, "zig fmt: off")) {
             // Write with the canonical single space.
             try ais.writer().writeAll("// zig fmt: off\n");