one_member_abstracts support for augmented classes

Fixes: https://github.com/dart-lang/linter/issues/4924

Change-Id: Ib51ba2dbbb4c4c27a582606b988ed42b4f5260ec
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/362191
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Phil Quitslund <[email protected]>

Author: pq

pkg/linter/lib/src/extensions.dart

@@ -124,6 +124,18 @@ extension BlockExtension on Block {
 }
 
 extension ClassElementExtension on ClassElement {
+  /// Get all fields, including merged augmentations.
+  List<FieldElement> get allFields => augmented?.fields ?? fields;
+
+  /// Get all interfaces, including merged augmentations.
+  List<InterfaceType> get allInterfaces => augmented?.interfaces ?? interfaces;
+
+  /// Get all methods, including merged augmentations.
+  List<MethodElement> get allMethods => augmented?.methods ?? methods;
+
+  /// Get all mixins, including merged augmentations.
+  List<InterfaceType> get allMixins => augmented?.mixins ?? mixins;
+
   bool get hasSubclassInDefiningCompilationUnit {
     var compilationUnit = library.definingCompilationUnit;
     for (var cls in compilationUnit.classes) {

pkg/linter/lib/src/rules/one_member_abstracts.dart

@@ -6,6 +6,7 @@ import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 
 import '../analyzer.dart';
+import '../extensions.dart';
 
 const _desc =
     r'Avoid defining a one-member abstract class when a simple function will do.';
@@ -66,26 +67,24 @@ class _Visitor extends SimpleAstVisitor<void> {
 
   @override
   void visitClassDeclaration(ClassDeclaration node) {
-    var declaredElement = node.declaredElement;
-    if (declaredElement == null) {
-      return;
-    }
-    if (declaredElement.interfaces.isNotEmpty) {
-      return;
-    }
-    if (declaredElement.mixins.isNotEmpty) {
-      return;
-    }
-    if (node.abstractKeyword != null &&
-        node.extendsClause == null &&
-        node.members.length == 1) {
-      var member = node.members.first;
-      if (member is MethodDeclaration &&
-          member.isAbstract &&
-          !member.isGetter &&
-          !member.isSetter) {
-        rule.reportLintForToken(node.name, arguments: [member.name.lexeme]);
-      }
+    if (node.abstractKeyword == null) return;
+    if (node.extendsClause != null) return;
+
+    if (node.isAugmentation) return;
+
+    var element = node.declaredElement;
+    if (element == null) return;
+
+    if (element.allInterfaces.isNotEmpty) return;
+    if (element.allMixins.isNotEmpty) return;
+    if (element.allFields.isNotEmpty) return;
+
+    var methods = element.allMethods;
+    if (methods.length != 1) return;
+
+    var method = methods.first;
+    if (method.isAbstract) {
+      rule.reportLintForToken(node.name, arguments: [method.name]);
     }
   }
 }

pkg/linter/test/rules/one_member_abstracts_test.dart

@@ -47,6 +47,40 @@ mixin M {
 ''');
   }
 
+  test_oneMember_augmentedAbstractClass_augmentation() async {
+    newFile('$testPackageLibPath/a.dart', r'''
+import augment 'test.dart';
+
+abstract class A { }
+''');
+
+    await assertNoDiagnostics(r'''
+augment library 'a.dart';
+
+augment abstract class A {
+  void m();
+}
+''');
+  }
+
+  test_oneMember_augmentedAbstractClass_declaration() async {
+    newFile('$testPackageLibPath/a.dart', r'''
+augment library 'test.dart';
+
+augment abstract class A {
+  void m();
+}
+''');
+
+    await assertDiagnostics(r'''
+import augment 'a.dart';
+
+abstract class A { }
+''', [
+      lint(41, 1),
+    ]);
+  }
+
   test_oneMember_extendedType() async {
     await assertNoDiagnostics(r'''
 abstract class D extends C {
@@ -96,7 +130,32 @@ sealed class C {
 ''');
   }
 
-  test_twoMembers() async {
+  test_twoMembers_augmentedAbstractClass_declaration() async {
+    newFile('$testPackageLibPath/a.dart', r'''
+augment library 'test.dart';
+
+augment abstract class A {
+  void m();
+}
+''');
+
+    newFile('$testPackageLibPath/b.dart', r'''
+augment library 'test.dart';
+
+augment abstract class A {
+  void n();
+}
+''');
+
+    await assertNoDiagnostics(r'''
+import augment 'a.dart';
+import augment 'b.dart';
+
+abstract class A { }
+''');
+  }
+
+  test_twoMembers_oneField() async {
     await assertNoDiagnostics(r'''
 abstract class C {
   int x = 0;
@@ -105,6 +164,15 @@ abstract class C {
 ''');
   }
 
+  test_twoMembers_oneGetter() async {
+    await assertNoDiagnostics(r'''
+abstract class C {
+  int get x => 0;
+  int f();
+}
+''');
+  }
+
   test_zeroMember_extendedTypeHasOneMember() async {
     await assertDiagnostics(r'''
 abstract class D extends C {}