| // Copyright (c) 2015, 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/visitor.dart'; |
| |
| import '../analyzer.dart'; |
| |
| const _desc = |
| r'Avoid defining a one-member abstract class when a simple function will do.'; |
| |
| const _details = r''' |
| |
| From the [style guide](https://dart.dev/guides/language/effective-dart/style/): |
| |
| **AVOID** defining a one-member abstract class when a simple function will do. |
| |
| Unlike Java, Dart has first-class functions, closures, and a nice light syntax |
| for using them. If all you need is something like a callback, just use a |
| function. If you're defining a class and it only has a single abstract member |
| with a meaningless name like `call` or `invoke`, there is a good chance |
| you just want a function. |
| |
| **GOOD:** |
| ``` |
| typedef bool Predicate(item); |
| ``` |
| |
| **BAD:** |
| ``` |
| abstract class Predicate { |
| bool test(item); |
| } |
| ``` |
| |
| '''; |
| |
| class OneMemberAbstracts extends LintRule implements NodeLintRule { |
| OneMemberAbstracts() |
| : super( |
| name: 'one_member_abstracts', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| final visitor = _Visitor(this); |
| registry.addClassDeclaration(this, visitor); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final LintRule rule; |
| |
| _Visitor(this.rule); |
| |
| @override |
| void visitClassDeclaration(ClassDeclaration node) { |
| if (node.declaredElement.interfaces.isNotEmpty) { |
| return; |
| } |
| if (node.declaredElement.mixins.isNotEmpty) { |
| return; |
| } |
| if (node.isAbstract && |
| node.extendsClause == null && |
| node.members.length == 1) { |
| var member = node.members[0]; |
| if (member is MethodDeclaration && |
| member.isAbstract && |
| !member.isGetter && |
| !member.isSetter) { |
| rule.reportLint(node.name); |
| } |
| } |
| } |
| } |