skip files with only known annotation names

source_gen/CHANGELOG.md

@@ -6,6 +6,8 @@
   For questions please use https://github.com/dart-lang/build/discussions.
 - Updated the minimum package versions for a number of dependencies.
 - Require Dart 3.7.0
+- Update the GeneratorForAnnotation optimization to skip files with well known
+  annotation names such as `override`, `Deprecated`, and `pragma`.
 
 ## 2.0.0
 

source_gen/lib/src/builder.dart

@@ -93,7 +93,7 @@ class _Builder extends Builder {
     if (!await resolver.isLibrary(buildStep.inputId)) return;
 
     if (_generators.every((g) => g is GeneratorForAnnotation) &&
-        !(await _hasAnyTopLevelAnnotations(
+        !(await _hasInterestingTopLevelAnnotations(
           buildStep.inputId,
           resolver,
           buildStep,
@@ -382,7 +382,7 @@ Stream<GeneratedOutput> _generate(
   }
 }
 
-Future<bool> _hasAnyTopLevelAnnotations(
+Future<bool> _hasInterestingTopLevelAnnotations(
   AssetId input,
   Resolver resolver,
   BuildStep buildStep,
@@ -399,16 +399,30 @@ Future<bool> _hasAnyTopLevelAnnotations(
     }
   }
   for (var declaration in parsed.declarations) {
-    if (declaration.metadata.isNotEmpty) return true;
+    if (declaration.metadata.any(_isUnknownAnnotation)) {
+      return true;
+    }
   }
   for (var partId in partIds) {
-    if (await _hasAnyTopLevelAnnotations(partId, resolver, buildStep)) {
+    if (await _hasInterestingTopLevelAnnotations(partId, resolver, buildStep)) {
       return true;
     }
   }
   return false;
 }
 
+bool _isUnknownAnnotation(Annotation annotation) {
+  const knownAnnotationNames = {
+    // Annotations from dart:core, there is an assumption that people are not
+    // overriding these.
+    'deprecated',
+    'Deprecated',
+    'override',
+    'pragma',
+  };
+  return !knownAnnotationNames.contains(annotation.name.name);
+}
+
 const defaultFileHeader = '// GENERATED CODE - DO NOT MODIFY BY HAND';
 
 String _defaultFormatOutput(String code, Version version) =>

source_gen/test/generator_for_annotation_test.dart

@@ -99,32 +99,37 @@ $dartFormatWidth
     }
   });
 
-  test(
-    'Does not resolve the library if there are no top level annotations',
-    () async {
-      final builder = LibraryBuilder(
-        _StubGenerator<Deprecated>('Deprecated', elementBehavior: (_) => null),
-      );
-      final input = AssetId('a', 'lib/a.dart');
-      final assets = {input: 'main() {}'};
-
-      final readerWriter =
-          TestReaderWriter()..testing.writeString(input, assets[input]!);
-
-      final resolver = _TestingResolver(assets);
-
-      await runBuilder(
-        builder,
-        [input],
-        readerWriter,
-        readerWriter,
-        _FixedResolvers(resolver),
-      );
+  test('Does not resolve the library if there are no interesting top level '
+      'annotations', () async {
+    final builder = LibraryBuilder(
+      _StubGenerator<Deprecated>('Deprecated', elementBehavior: (_) => null),
+    );
+    final input = AssetId('a', 'lib/a.dart');
+    final assets = {
+      input: '''
+@Deprecated()
+@deprecated
+@override
+@pragma('')
+main() {}''',
+    };
+
+    final readerWriter =
+        TestReaderWriter()..testing.writeString(input, assets[input]!);
+
+    final resolver = _TestingResolver(assets);
+
+    await runBuilder(
+      builder,
+      [input],
+      readerWriter,
+      readerWriter,
+      _FixedResolvers(resolver),
+    );
 
-      expect(resolver.parsedUnits, {input});
-      expect(resolver.resolvedLibs, isEmpty);
-    },
-  );
+    expect(resolver.parsedUnits, {input});
+    expect(resolver.resolvedLibs, isEmpty);
+  });
 
   test('applies to annotated libraries', () async {
     final builder = LibraryBuilder(