| // 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/token.dart'; |
| import 'package:analyzer/dart/ast/visitor.dart'; |
| import 'package:analyzer/dart/element/type.dart'; |
| |
| import '../analyzer.dart'; |
| import '../util/dart_type_utilities.dart'; |
| |
| const alwaysFalse = |
| 'Always false because indexOf is always greater or equal -1.'; |
| |
| const alwaysTrue = 'Always true because indexOf is always greater or equal -1.'; |
| |
| const useContains = 'Use contains instead of indexOf'; |
| const _desc = r'Use contains for `List` and `String` instances.'; |
| |
| const _details = r''' |
| |
| **DON'T** use `indexOf` to see if a collection contains an element. |
| |
| Calling `indexOf` to see if a collection contains something is difficult to read |
| and may have poor performance. |
| |
| Instead, prefer `contains`. |
| |
| **GOOD:** |
| ``` |
| if (!lunchBox.contains('sandwich') return 'so hungry...'; |
| ``` |
| |
| **BAD:** |
| ``` |
| if (lunchBox.indexOf('sandwich') == -1 return 'so hungry...'; |
| ``` |
| |
| '''; |
| |
| class PreferContainsOverIndexOf extends LintRule implements NodeLintRule { |
| PreferContainsOverIndexOf() |
| : super( |
| name: 'prefer_contains', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| final visitor = _Visitor(this, context); |
| registry.addSimpleIdentifier(this, visitor); |
| } |
| |
| void reportLintWithDescription(AstNode node, String description) { |
| if (node != null) { |
| reporter.reportErrorForNode(_LintCode(name, description), node, []); |
| } |
| } |
| } |
| |
| /// TODO create common MultiMessageLintCode class |
| class _LintCode extends LintCode { |
| static final registry = <String, _LintCode>{}; |
| |
| factory _LintCode(String name, String message) => |
| registry.putIfAbsent(name + message, () => _LintCode._(name, message)); |
| |
| _LintCode._(String name, String message) : super(name, message); |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final PreferContainsOverIndexOf rule; |
| |
| final LinterContext context; |
| |
| _Visitor(this.rule, this.context); |
| |
| @override |
| void visitSimpleIdentifier(SimpleIdentifier node) { |
| // Should be "indexOf". |
| final propertyElement = node.staticElement; |
| if (propertyElement?.name != 'indexOf') { |
| return; |
| } |
| |
| MethodInvocation indexOfAccess; |
| InterfaceType type; |
| |
| final parent = node.parent; |
| if (parent is MethodInvocation && node == parent.methodName) { |
| indexOfAccess = parent; |
| var parentType = parent.target?.staticType; |
| if (parentType is! InterfaceType) { |
| return; |
| } |
| type = parentType as InterfaceType; |
| } else { |
| return; |
| } |
| |
| if (!DartTypeUtilities.implementsAnyInterface( |
| type, <InterfaceTypeDefinition>[ |
| InterfaceTypeDefinition('Iterable', 'dart.core'), |
| InterfaceTypeDefinition('String', 'dart.core'), |
| ])) { |
| return; |
| } |
| |
| if (indexOfAccess.parent is AssignmentExpression) { |
| // The result of `indexOf` is being assigned before being compared, so |
| // it's important. E.g. `(next = list.indexOf('{')) != -1)`. |
| return; |
| } |
| |
| // Going up in AST structure to find binary comparison operator for this |
| // `indexOf` access. Most of the time it will be a parent, but sometimes |
| // it can be wrapped in parentheses or `as` operator. |
| AstNode search = indexOfAccess; |
| while ( |
| search != null && search is Expression && search is! BinaryExpression) { |
| search = search.parent; |
| } |
| |
| if (search is! BinaryExpression) { |
| return; |
| } |
| |
| final binaryExpression = search as BinaryExpression; |
| final operator = binaryExpression.operator; |
| |
| // Comparing constants with result of indexOf. |
| |
| final rightOperand = binaryExpression.rightOperand; |
| final rightValue = context.evaluateConstant(rightOperand).value; |
| |
| if (rightValue?.type?.isDartCoreInt == true) { |
| // Constant is on right side of comparison operator |
| _checkConstant(binaryExpression, rightValue.toIntValue(), operator.type); |
| return; |
| } |
| |
| final leftOperand = binaryExpression.leftOperand; |
| final leftValue = context.evaluateConstant(leftOperand).value; |
| if (leftValue?.type?.isDartCoreInt == true) { |
| // Constants is on left side of comparison operator |
| _checkConstant(binaryExpression, leftValue.toIntValue(), |
| _invertedTokenType(operator.type)); |
| } |
| } |
| |
| void _checkConstant(Expression expression, int value, TokenType type) { |
| if (value == -1) { |
| if (type == TokenType.EQ_EQ || |
| type == TokenType.BANG_EQ || |
| type == TokenType.LT_EQ || |
| type == TokenType.GT) { |
| rule.reportLintWithDescription(expression, useContains); |
| } else if (type == TokenType.LT) { |
| // indexOf < -1 is always false |
| rule.reportLintWithDescription(expression, alwaysFalse); |
| } else if (type == TokenType.GT_EQ) { |
| // indexOf >= -1 is always true |
| rule.reportLintWithDescription(expression, alwaysTrue); |
| } |
| } else if (value == 0) { |
| // 'indexOf >= 0' is same as 'contains', |
| // and 'indexOf < 0' is same as '!contains' |
| if (type == TokenType.GT_EQ || type == TokenType.LT) { |
| rule.reportLintWithDescription(expression, useContains); |
| } |
| } else if (value < -1) { |
| // 'indexOf' is always >= -1, so comparing with lesser values makes |
| // no sense. |
| if (type == TokenType.EQ_EQ || |
| type == TokenType.LT_EQ || |
| type == TokenType.LT) { |
| rule.reportLintWithDescription(expression, alwaysFalse); |
| } else if (type == TokenType.BANG_EQ || |
| type == TokenType.GT_EQ || |
| type == TokenType.GT) { |
| rule.reportLintWithDescription(expression, alwaysTrue); |
| } |
| } |
| } |
| |
| TokenType _invertedTokenType(TokenType type) { |
| switch (type) { |
| case TokenType.LT_EQ: |
| return TokenType.GT_EQ; |
| |
| case TokenType.LT: |
| return TokenType.GT; |
| |
| case TokenType.GT: |
| return TokenType.LT; |
| |
| case TokenType.GT_EQ: |
| return TokenType.LT_EQ; |
| |
| default: |
| return type; |
| } |
| } |
| } |