| // Copyright (c) 2019, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| import 'package:analyzer/dart/ast/ast.dart'; |
| import 'package:analyzer/dart/ast/token.dart'; |
| import 'package:analyzer/dart/ast/visitor.dart'; |
| import 'package:analyzer/dart/element/element.dart'; |
| |
| import '../analyzer.dart'; |
| import '../ast.dart'; |
| |
| const _desc = |
| r'AVOID overloading operator == and hashCode on classes not marked `@immutable`.'; |
| |
| const _details = r''' |
| |
| **AVOID** overloading operator == and hashCode on classes not marked `@immutable`. |
| |
| If a class is not immutable, overloading operator == and hashCode can lead to |
| unpredictable and undesirable behavior when used in collections. See |
| https://dart.dev/guides/language/effective-dart/design#avoid-defining-custom-equality-for-mutable-classes |
| for more information. |
| |
| **GOOD:** |
| ``` |
| @immutable |
| class A { |
| final String key; |
| const A(this.key); |
| @override |
| operator ==(other) => other is A && other.key == key; |
| @override |
| int hashCode() => key.hashCode; |
| } |
| ``` |
| |
| **BAD:** |
| ``` |
| class B { |
| String key; |
| const B(this.key); |
| @override |
| operator ==(other) => other is B && other.key == key; |
| @override |
| int hashCode() => key.hashCode; |
| } |
| ``` |
| |
| NOTE: The lint checks the use of the @immutable annotation, and will trigger |
| even if the class is otherwise not mutable. Thus: |
| |
| **BAD:** |
| ``` |
| class C { |
| final String key; |
| const C(this.key); |
| @override |
| operator ==(other) => other is B && other.key == key; |
| @override |
| int hashCode() => key.hashCode; |
| } |
| ``` |
| |
| '''; |
| |
| /// The name of the top-level variable used to mark a immutable class. |
| String _IMMUTABLE_VAR_NAME = 'immutable'; |
| |
| /// The name of `meta` library, used to define analysis annotations. |
| String _META_LIB_NAME = 'meta'; |
| |
| bool _isImmutable(Element element) => |
| element is PropertyAccessorElement && |
| element.name == _IMMUTABLE_VAR_NAME && |
| element.library?.name == _META_LIB_NAME; |
| |
| class AvoidOperatorEqualsOnMutableClasses extends LintRule |
| implements NodeLintRule { |
| AvoidOperatorEqualsOnMutableClasses() |
| : super( |
| name: 'avoid_equals_and_hash_code_on_mutable_classes', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| final visitor = _Visitor(this, context); |
| registry.addMethodDeclaration(this, visitor); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final LintRule rule; |
| |
| final LinterContext context; |
| |
| _Visitor(this.rule, this.context); |
| |
| @override |
| void visitMethodDeclaration(MethodDeclaration node) { |
| if (node.name.token?.type == TokenType.EQ_EQ || isHashCode(node)) { |
| final classElement = _getClassForMethod(node); |
| if (classElement != null && !_hasImmutableAnnotation(classElement)) { |
| rule.reportLintForToken(node.firstTokenAfterCommentAndMetadata); |
| } |
| } |
| } |
| |
| ClassElement _getClassForMethod(MethodDeclaration node) => |
| node.parent.thisOrAncestorOfType<ClassDeclaration>()?.declaredElement; |
| |
| bool _hasImmutableAnnotation(ClassElement clazz) { |
| final inheritedAndSelfElements = <ClassElement>[ |
| ...clazz.allSupertypes.map((t) => t.element), |
| clazz, |
| ]; |
| final inheritedAndSelfAnnotations = inheritedAndSelfElements |
| .expand((c) => c.metadata) |
| .map((m) => m.element); |
| return inheritedAndSelfAnnotations.any(_isImmutable); |
| } |
| } |