| // 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 'package:linter/src/analyzer.dart'; |
| import 'package:linter/src/util/dart_type_utilities.dart'; |
| |
| const _desc = r'Use `forEach` to only apply a function to all the elements.'; |
| |
| const _details = r''' |
| |
| **DO** use `forEach` if you are only going to apply a function or a method |
| to all the elements of an iterable. |
| |
| Using `forEach` when you are only going to apply a function or method to all |
| elements of an iterable is a good practice because it makes your code more |
| terse. |
| |
| **BAD:** |
| ``` |
| for (final key in map.keys.toList()) { |
| map.remove(key); |
| } |
| ``` |
| |
| **GOOD:** |
| ``` |
| map.keys.toList().forEach(map.remove); |
| ``` |
| |
| **NOTE:** Replacing a for each statement with a forEach call may change the |
| behavior in the case where there are side-effects on the iterable itself. |
| ``` |
| for (final v in myList) { |
| foo().f(v); // This code invokes foo() many times. |
| } |
| |
| myList.forEach(foo().f); // But this one invokes foo() just once. |
| ``` |
| |
| '''; |
| |
| class PreferForeach extends LintRule implements NodeLintRule { |
| PreferForeach() |
| : super( |
| name: 'prefer_foreach', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| void registerNodeProcessors(NodeLintRegistry registry, |
| [LinterContext context]) { |
| final visitor = new _Visitor(this); |
| registry.addForEachStatement(this, visitor); |
| } |
| } |
| |
| class _PreferForEachVisitor extends SimpleAstVisitor { |
| final LintRule rule; |
| LocalVariableElement element; |
| ForEachStatement forEachStatement; |
| |
| _PreferForEachVisitor(this.rule); |
| |
| @override |
| visitBlock(Block node) { |
| if (node.statements.length == 1) { |
| node.statements.first.accept(this); |
| } |
| } |
| |
| @override |
| visitExpressionStatement(ExpressionStatement node) { |
| node.expression.accept(this); |
| } |
| |
| @override |
| visitForEachStatement(ForEachStatement node) { |
| final element = node.loopVariable?.declaredElement; |
| if (element != null) { |
| forEachStatement = node; |
| this.element = element; |
| node.body.accept(this); |
| } |
| } |
| |
| @override |
| visitFunctionExpressionInvocation(FunctionExpressionInvocation node) { |
| final arguments = node.argumentList.arguments; |
| if (arguments.length == 1 && |
| DartTypeUtilities.getCanonicalElementFromIdentifier(arguments.first) == |
| element) { |
| rule.reportLint(forEachStatement); |
| } |
| } |
| |
| @override |
| visitMethodInvocation(MethodInvocation node) { |
| final arguments = node.argumentList.arguments; |
| if (arguments.length == 1 && |
| DartTypeUtilities.getCanonicalElementFromIdentifier(arguments.first) == |
| element && |
| (node.target == null || |
| (DartTypeUtilities.getCanonicalElementFromIdentifier(node.target) != |
| element && |
| !DartTypeUtilities.traverseNodesInDFS(node.target) |
| .map(DartTypeUtilities.getCanonicalElementFromIdentifier) |
| .contains(element)))) { |
| rule.reportLint(forEachStatement); |
| } |
| } |
| |
| @override |
| visitParenthesizedExpression(ParenthesizedExpression node) { |
| node.unParenthesized.accept(this); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor { |
| final LintRule rule; |
| _Visitor(this.rule); |
| |
| @override |
| visitForEachStatement(ForEachStatement node) { |
| final visitor = new _PreferForEachVisitor(rule); |
| node.accept(visitor); |
| } |
| } |