| // Copyright (c) 2017, 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 'package:analyzer/dart/element/element.dart'; |
| |
| import '../analyzer.dart'; |
| |
| const _desc = r'Avoid defining a class that contains only static members.'; |
| |
| const _details = r''' |
| |
| **AVOID** defining a class that contains only static members. |
| |
| Creating classes with the sole purpose of providing utility or otherwise static |
| methods is discouraged. Dart allows functions to exist outside of classes for |
| this very reason. |
| |
| **BAD:** |
| ``` |
| class DateUtils { |
| static DateTime mostRecent(List<DateTime> dates) { |
| return dates.reduce((a, b) => a.isAfter(b) ? a : b); |
| } |
| } |
| |
| class _Favorites { |
| static const mammal = 'weasel'; |
| } |
| ``` |
| |
| **GOOD:** |
| ``` |
| DateTime mostRecent(List<DateTime> dates) { |
| return dates.reduce((a, b) => a.isAfter(b) ? a : b); |
| } |
| |
| const _favoriteMammal = 'weasel'; |
| ``` |
| |
| '''; |
| |
| bool _isNonConst(FieldElement element) => !element.isConst; |
| |
| bool _isStaticMember(ClassMember classMember) { |
| if (classMember is MethodDeclaration) { |
| return classMember.isStatic; |
| } |
| if (classMember is FieldDeclaration) { |
| return classMember.isStatic; |
| } |
| return false; |
| } |
| |
| class AvoidClassesWithOnlyStaticMembers extends LintRule |
| implements NodeLintRule { |
| AvoidClassesWithOnlyStaticMembers() |
| : super( |
| name: 'avoid_classes_with_only_static_members', |
| 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.members.isNotEmpty && |
| node.members.every(_isStaticMember) && |
| node.declaredElement.fields.any(_isNonConst)) { |
| rule.reportLint(node); |
| } |
| } |
| } |