Support accessing the documentation comment of an ExtensionElement

Change-Id: If433a7e795369a195a917653f303c71df84a4a0c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/110000
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Phil Quitslund <pquitslund@google.com>

pkg/analyzer/lib/src/dart/element/element.dart

@@ -5019,6 +5019,19 @@ class ExtensionElementImpl extends ElementImpl
   @override
   String get displayName => name;
 
+  @override
+  String get documentationComment {
+    if (linkedNode != null) {
+      var context = enclosingUnit.linkedContext;
+      var comment = context.getDocumentationComment(linkedNode);
+      return getCommentNodeRawText(comment);
+    }
+    if (_unlinkedExtension != null) {
+      return _unlinkedExtension.documentationComment?.text;
+    }
+    return super.documentationComment;
+  }
+
   @override
   TypeParameterizedElementMixin get enclosingTypeParameterContext => null;
 

pkg/analyzer/lib/src/summary2/linked_unit_context.dart

@@ -256,6 +256,9 @@ class LinkedUnitContext {
     } else if (node is EnumDeclaration) {
       LazyEnumDeclaration.readDocumentationComment(this, node);
       return node.documentationComment;
+    } else if (node is ExtensionDeclaration) {
+      LazyExtensionDeclaration.readDocumentationComment(this, node);
+      return node.documentationComment;
     } else if (node is FunctionDeclaration) {
       LazyFunctionDeclaration.readDocumentationComment(this, node);
       return node.documentationComment;

pkg/analyzer/test/src/summary/element_text.dart

@@ -331,6 +331,26 @@ class _ElementWriter {
     }
   }
 
+  void writeExtensionElement(ExtensionElement e) {
+    writeDocumentation(e);
+    writeMetadata(e, '', '\n');
+
+    buffer.write('extension ');
+    writeName(e);
+    writeCodeRange(e);
+    writeTypeParameterElements(e.typeParameters);
+    if (e.extendedType != null) {
+      buffer.write(' on ');
+      writeType(e.extendedType);
+    }
+
+    buffer.writeln(' {');
+    e.fields.forEach(writePropertyInducingElement);
+    e.accessors.forEach(writePropertyAccessorElement);
+    e.methods.forEach(writeMethodElement);
+    buffer.writeln('}');
+  }
+
   void writeFunctionElement(FunctionElement e) {
     writeDocumentation(e);
     writeMetadata(e, '', '\n');
@@ -1016,6 +1036,7 @@ class _ElementWriter {
     e.enums.forEach(writeClassElement);
     e.types.forEach(writeClassElement);
     e.mixins.forEach(writeClassElement);
+    e.extensions.forEach(writeExtensionElement);
     e.topLevelVariables.forEach(writePropertyInducingElement);
     e.accessors.forEach(writePropertyAccessorElement);
     e.functions.forEach(writeFunctionElement);

pkg/analyzer/test/src/summary/resynthesize_ast2_test.dart

@@ -136,6 +136,12 @@ class ResynthesizeAst2Test extends ResynthesizeTestStrategyTwoPhase
     return elementFactory.libraryOfUri('${source.uri}');
   }
 
+  @failingTest
+  @override
+  test_extension_documented_tripleSlash() async {
+    await super.test_extension_documented_tripleSlash();
+  }
+
   void _addLibraryUnits(
     Source definingSource,
     CompilationUnit definingUnit,

pkg/analyzer/test/src/summary/resynthesize_common.dart

@@ -208,6 +208,9 @@ mixin GetElementTestCases implements ResynthesizeTestHelpers {
 mixin ResynthesizeTestCases implements ResynthesizeTestHelpers {
   FeatureSet get disableNnbd => FeatureSet.forTesting(sdkVersion: '2.2.2');
 
+  FeatureSet get enableExtensionMethods =>
+      FeatureSet.forTesting(additionalFeatures: [Feature.extension_methods]);
+
   FeatureSet get enableNnbd =>
       FeatureSet.forTesting(additionalFeatures: [Feature.non_nullable]);
 
@@ -5851,6 +5854,22 @@ class C<T> {
 ''');
   }
 
+  test_extension_documented_tripleSlash() async {
+    featureSet = enableExtensionMethods;
+    var library = await checkLibrary('''
+/// aaa
+/// bbbb
+/// cc
+extension E on int {}''');
+    checkElementText(library, r'''
+/// aaa
+/// bbbb
+/// cc
+extension E on int {
+}
+''');
+  }
+
   test_field_covariant() async {
     var library = await checkLibrary('''
 class C {
@@ -9580,21 +9599,6 @@ int y;
 ''');
   }
 
-  test_type_inference_fieldFormal_depends_onField() async {
-    var library = await checkLibrary('''
-class A<T> {
-  var f = 0;
-  A(this.f);
-}
-''');
-    checkElementText(library, r'''
-class A<T> {
-  int f;
-  A(int this.f);
-}
-''');
-  }
-
   test_type_inference_field_depends_onFieldFormal() async {
     var library = await checkLibrary('''
 class A<T> {
@@ -9618,6 +9622,21 @@ class B {
 ''');
   }
 
+  test_type_inference_fieldFormal_depends_onField() async {
+    var library = await checkLibrary('''
+class A<T> {
+  var f = 0;
+  A(this.f);
+}
+''');
+    checkElementText(library, r'''
+class A<T> {
+  int f;
+  A(int this.f);
+}
+''');
+  }
+
   test_type_inference_multiplyDefinedElement() async {
     addLibrarySource('/a.dart', 'class C {}');
     addLibrarySource('/b.dart', 'class C {}');