Add new experimental_collect_validations_metadata .gn variable

And associated --experimental-collect-validations-metadata
switch.

This is not connected to anything right now.

Bug: 566346002
Change-Id: Id374c42d29cca4d6cd62367596dc81f14fa5198e
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/27084
Reviewed-by: Takuto Ikuta <tikuta@google.com>
Commit-Queue: David Turner <digit@google.com>

docs/reference.md

@@ -7828,6 +7828,14 @@
       A boolean flag that can be set to generate Ninja files that use phony
       rules instead of stamp files whenever possible. This results in smaller
       Ninja build plans, but requires at least Ninja 1.11.
+
+  experimental_collect_validations_metadata [optional]
+      NOTE: This flag is experimental and will be removed in the future.
+
+      A boolean flag that determines whether generated_file() metadata walks
+      should include validations targets's metadata. This is false by default
+      but may be required temporarily by the Fuchsia build. See
+      https://gn.g-issues.chromium.org/issues/566346002 for details.
 ```
 
 #### **Example .gn file contents**
@@ -8880,6 +8888,7 @@
     *   --dotfile: Override the name of the ".gn" file.
     *   --enumerate-files-with-git: Use git to list files.
     *   --error-limit: Limit the number of errors or warnings to print.
+    *   --experimental-collect-validations-metadata: Collect metadata from validations.
     *   --fail-on-unused-args: Treat unused build args as fatal errors.
     *   --format-width: Set the formatting width (default is 80)
     *   --markdown: Write help output in the Markdown format.

src/gn/build_settings.h

@@ -165,6 +165,15 @@ class BuildSettings {
     allow_circular_includes_from_allowlist_ = std::move(list);
   }
 
+  // If true, all generated_file() metadata walks include metadata from
+  // validations targets.
+  bool experimental_collect_validations_metadata() const {
+    return experimental_collect_validations_metadata_;
+  }
+  void set_experimental_collect_validations_metadata(bool value) {
+    experimental_collect_validations_metadata_ = value;
+  }
+
  private:
   Label root_target_label_;
   std::vector<LabelPattern> root_patterns_;
@@ -178,6 +187,7 @@ class BuildSettings {
   // See 40045b9 for the reason behind using 1.7.2 as the default version.
   Version ninja_required_version_{1, 7, 2};
   bool no_stamp_files_ = true;
+  bool experimental_collect_validations_metadata_ = false;
 
   SourceFile build_config_file_;
   SourceFile arg_file_template_path_;

src/gn/setup.cc

@@ -260,6 +260,14 @@ Variables
       rules instead of stamp files whenever possible. This results in smaller
       Ninja build plans, but requires at least Ninja 1.11.
 
+  experimental_collect_validations_metadata [optional]
+      NOTE: This flag is experimental and will be removed in the future.
+
+      A boolean flag that determines whether generated_file() metadata walks
+      should include validations targets's metadata. This is false by default
+      but may be required temporarily by the Fuchsia build. See
+      https://gn.g-issues.chromium.org/issues/566346002 for details.
+
 Example .gn file contents
 
   buildconfig = "//build/config/BUILDCONFIG.gn"
@@ -1302,5 +1310,23 @@ bool Setup::FillOtherConfig(const base::CommandLine& cmdline, Err* err) {
     export_compile_commands_.push_back(std::move(pat));
   }
 
+  // Collect validations metadata during generate_file() walks.
+  // See https://gn.g-issues.chromium.org/issues/566346002
+  if (cmdline.HasSwitch(switches::kExperimentalCollectValidationsMetadata)) {
+    build_settings_.set_experimental_collect_validations_metadata(true);
+  } else {
+    const Value* experimental_collect_validations_metadata_value =
+        dotfile_scope_.GetValue("experimental_collect_validations_metadata",
+                                true);
+    if (experimental_collect_validations_metadata_value) {
+      if (!experimental_collect_validations_metadata_value->VerifyTypeIs(
+              Value::BOOLEAN, err)) {
+        return false;
+      }
+      build_settings_.set_experimental_collect_validations_metadata(
+          experimental_collect_validations_metadata_value->boolean_value());
+    }
+  }
+
   return true;
 }

src/gn/switches.cc

@@ -88,6 +88,20 @@ const char kErrorLimit_Help[] =
   and warnings without any limit.
 )";
 
+const char kExperimentalCollectValidationsMetadata[] =
+    "experimental-collect-validations-metadata";
+const char kExperimentalCollectValidationsMetadata_HelpShort[] =
+    "--experimental-collect-validations-metadata: Collect metadata from "
+    "validations.";
+const char kExperimentalCollectValidationsMetadata_Help[] =
+    R"(--experimental-collect-validations-metadata: Collect metadata from validations.
+
+  Sets the default value of generated_file() collect_validations_metadata
+  argument to true (default is false).
+
+  This switch is experimental and will be removed in the future.
+  See https://issuetracker.google.com/566346002.
+)";
 const char kFailOnUnusedArgs[] = "fail-on-unused-args";
 const char kFailOnUnusedArgs_HelpShort[] =
     "--fail-on-unused-args: Treat unused build args as fatal errors.";
@@ -373,6 +387,7 @@ const SwitchInfoMap& GetSwitches() {
     INSERT_VARIABLE(Dotfile)
     INSERT_VARIABLE(EnumerateFilesWithGit)
     INSERT_VARIABLE(ErrorLimit)
+    INSERT_VARIABLE(ExperimentalCollectValidationsMetadata)
     INSERT_VARIABLE(FailOnUnusedArgs)
     INSERT_VARIABLE(FormatWidth)
     INSERT_VARIABLE(Markdown)

src/gn/switches.h

@@ -46,6 +46,10 @@ extern const char kErrorLimit[];
 extern const char kErrorLimit_HelpShort[];
 extern const char kErrorLimit_Help[];
 
+extern const char kExperimentalCollectValidationsMetadata[];
+extern const char kExperimentalCollectValidationsMetadata_HelpShort[];
+extern const char kExperimentalCollectValidationsMetadata_Help[];
+
 extern const char kFailOnUnusedArgs[];
 extern const char kFailOnUnusedArgs_HelpShort[];
 extern const char kFailOnUnusedArgs_Help[];