| // Copyright (c) 2016, 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'; |
| import '../util/dart_type_utilities.dart'; |
| |
| const _desc = r'Await only futures.'; |
| |
| const _details = r''' |
| |
| **AVOID** using await on anything other than a future. |
| |
| **BAD:** |
| ``` |
| main() async { |
| print(await 23); |
| } |
| ``` |
| |
| **GOOD:** |
| ``` |
| main() async { |
| print(await Future.value(23)); |
| } |
| ``` |
| |
| '''; |
| |
| class AwaitOnlyFutures extends LintRule implements NodeLintRule { |
| AwaitOnlyFutures() |
| : super( |
| name: 'await_only_futures', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| final visitor = _Visitor(this); |
| registry.addAwaitExpression(this, visitor); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| static const LintCode _errorCode = LintCode('await_only_futures', |
| "'await' applied to '{0}', which is not a 'Future'."); |
| |
| final LintRule rule; |
| |
| _Visitor(this.rule); |
| |
| @override |
| void visitAwaitExpression(AwaitExpression node) { |
| if (node.expression is NullLiteral) return; |
| |
| final type = node.expression.staticType; |
| if (!(type == null || |
| type.isDartAsyncFuture || |
| type.isDynamic || |
| DartTypeUtilities.extendsClass(type, 'Future', 'dart.async') || |
| DartTypeUtilities.implementsInterface(type, 'Future', 'dart.async') || |
| DartTypeUtilities.isClass(type, 'FutureOr', 'dart.async'))) { |
| rule.reportLintForToken(node.awaitKeyword, |
| errorCode: _errorCode, arguments: [type]); |
| } |
| } |
| } |