| // Copyright (c) 2018, 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 async functions that return void.'; |
| |
| const _details = r''' |
| |
| **DO** mark async functions to return Future<void>. |
| |
| When declaring an async method or function which does not return a value, |
| declare that it returns Future<void> and not just void. |
| |
| **BAD:** |
| ``` |
| void f() async {} |
| void f2() async => null; |
| ``` |
| |
| **GOOD:** |
| ``` |
| Future<void> f() async {} |
| Future<void> f2() async => null; |
| ``` |
| |
| '''; |
| |
| class AvoidVoidAsync extends LintRule implements NodeLintRule { |
| AvoidVoidAsync() |
| : super( |
| name: 'avoid_void_async', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| final visitor = _Visitor(this); |
| registry.addFunctionDeclaration(this, visitor); |
| registry.addMethodDeclaration(this, visitor); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final LintRule rule; |
| |
| _Visitor(this.rule); |
| |
| @override |
| void visitFunctionDeclaration(FunctionDeclaration node) { |
| if (_isAsync(node.declaredElement) && _isVoid(node.returnType)) { |
| rule.reportLint(node.name); |
| } |
| } |
| |
| @override |
| void visitMethodDeclaration(MethodDeclaration node) { |
| if (_isAsync(node.declaredElement) && _isVoid(node.returnType)) { |
| rule.reportLint(node.name); |
| } |
| } |
| |
| bool _isAsync(ExecutableElement element) { |
| if (element == null) { |
| return false; |
| } |
| return element.isAsynchronous || element.isGenerator; |
| } |
| |
| bool _isVoid(TypeAnnotation typeAnnotation) => |
| typeAnnotation?.type?.isVoid ?? false; |
| } |