| // 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/token.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"Don't create a lambda when a tear-off will do."; |
| |
| const _details = r''' |
| |
| **DON'T** create a lambda when a tear-off will do. |
| |
| **BAD:** |
| ``` |
| names.forEach((name) { |
| print(name); |
| }); |
| ``` |
| |
| **GOOD:** |
| ``` |
| names.forEach(print); |
| ``` |
| |
| '''; |
| |
| bool _containsNullAwareInvocationInChain(AstNode node) => |
| node != null && |
| ((node is PropertyAccess && |
| (node.operator?.type == TokenType.QUESTION_PERIOD || |
| _containsNullAwareInvocationInChain(node.target))) || |
| (node is MethodInvocation && |
| (node.operator?.type == TokenType.QUESTION_PERIOD || |
| _containsNullAwareInvocationInChain(node.target))) || |
| (node is IndexExpression && |
| _containsNullAwareInvocationInChain(node.target))); |
| |
| Iterable<Element> _extractElementsOfSimpleIdentifiers(AstNode node) => |
| DartTypeUtilities |
| .traverseNodesInDFS(node) |
| .where((e) => e is SimpleIdentifier) |
| .map((e) => (e as SimpleIdentifier).bestElement); |
| |
| bool _isInvocationExpression(AstNode node) => node is InvocationExpression; |
| |
| bool _isNonFinalElement(Element element) => |
| (element is PropertyAccessorElement && |
| (!element.isSynthetic || !element.variable.isFinal)) || |
| (element is VariableElement && !element.isFinal); |
| |
| bool _isNonFinalField(AstNode node) => |
| (node is PropertyAccess && |
| _isNonFinalElement(node.propertyName.bestElement)) || |
| (node is MethodInvocation && |
| (_isNonFinalElement(node.methodName.bestElement))) || |
| (node is SimpleIdentifier && _isNonFinalElement(node.bestElement)); |
| |
| class UnnecessaryLambdas extends LintRule { |
| _Visitor _visitor; |
| |
| UnnecessaryLambdas() |
| : super( |
| name: 'unnecessary_lambdas', |
| description: _desc, |
| details: _details, |
| group: Group.style) { |
| _visitor = new _Visitor(this); |
| } |
| |
| @override |
| AstVisitor getVisitor() => _visitor; |
| } |
| |
| class _Visitor extends SimpleAstVisitor { |
| final LintRule rule; |
| _Visitor(this.rule); |
| |
| @override |
| void visitFunctionExpression(FunctionExpression node) { |
| if (node.element.name != '' || node.body.keyword != null) { |
| return; |
| } |
| final body = node.body; |
| if (body is BlockFunctionBody && body.block.statements.length == 1) { |
| final statement = body.block.statements.single; |
| if (statement is ExpressionStatement && |
| statement.expression is InvocationExpression) { |
| _visitInvocationExpression(statement.expression, node); |
| } else if (statement is ReturnStatement && |
| statement.expression is InvocationExpression) { |
| _visitInvocationExpression(statement.expression, node); |
| } |
| } else if (body is ExpressionFunctionBody) { |
| if (body.expression is InvocationExpression) { |
| _visitInvocationExpression(body.expression, node); |
| } |
| } |
| } |
| |
| void _visitInvocationExpression( |
| InvocationExpression node, FunctionExpression nodeToLint) { |
| if (!DartTypeUtilities.matchesArgumentsWithParameters( |
| node.argumentList.arguments, nodeToLint.parameters.parameters)) { |
| return; |
| } |
| final parameters = |
| nodeToLint.parameters.parameters.map((e) => e.identifier.bestElement); |
| |
| Iterable<Element> restOfElements = []; |
| if (node is FunctionExpressionInvocation) { |
| restOfElements = _extractElementsOfSimpleIdentifiers(node.function); |
| } else if (node is MethodInvocation) { |
| var nodesInTarget = <AstNode>[]; |
| if (node.target != null) { |
| nodesInTarget = DartTypeUtilities.traverseNodesInDFS(node.target); |
| restOfElements = node.target is SimpleIdentifier |
| ? [(node.target as SimpleIdentifier).bestElement] |
| : _extractElementsOfSimpleIdentifiers(node.target); |
| } |
| if (_isNonFinalField(node) || |
| _isNonFinalField(node.target) || |
| _isInvocationExpression(node.target) || |
| _containsNullAwareInvocationInChain(node) || |
| nodesInTarget.any(_isNonFinalField) || |
| nodesInTarget.any(_isInvocationExpression)) { |
| return; |
| } |
| } |
| if (restOfElements.any(parameters.contains)) { |
| return; |
| } |
| rule.reportLint(nodeToLint); |
| } |
| } |