| // Copyright (c) 2015, 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' |
| show |
| AstNode, |
| AstVisitor, |
| PrefixExpression, |
| PrefixedIdentifier, |
| PropertyAccess, |
| SimpleIdentifier; |
| import 'package:analyzer/dart/ast/token.dart'; |
| import 'package:analyzer/dart/ast/visitor.dart'; |
| import 'package:analyzer/dart/element/element.dart' show Element; |
| import 'package:linter/src/analyzer.dart'; |
| import 'package:linter/src/ast.dart'; |
| |
| const _desc = r'Use `isNotEmpty` for Iterables and Maps.'; |
| |
| const _details = r''' |
| |
| **PREFER** `x.isNotEmpty` to `!x.isEmpty` for `Iterable` and `Map` instances. |
| |
| When testing whether an iterable or map is empty, prefer `isNotEmpty` over |
| `!isEmpty` to improve code readability. |
| |
| **GOOD:** |
| ``` |
| if (todo.isNotEmpty) { |
| sendResults(request, todo.isEmpty); |
| } |
| ``` |
| |
| **BAD:** |
| ``` |
| if (!sources.isEmpty) { |
| process(sources); |
| } |
| ``` |
| |
| '''; |
| |
| class PreferIsNotEmpty extends LintRule { |
| PreferIsNotEmpty() |
| : super( |
| name: 'prefer_is_not_empty', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| AstVisitor getVisitor() => new Visitor(this); |
| } |
| |
| class Visitor extends SimpleAstVisitor { |
| final LintRule rule; |
| Visitor(this.rule); |
| |
| @override |
| visitSimpleIdentifier(SimpleIdentifier identifier) { |
| AstNode isEmptyAccess; |
| SimpleIdentifier isEmptyIdentifier; |
| |
| AstNode parent = identifier.parent; |
| if (parent is PropertyAccess) { |
| isEmptyIdentifier = parent.propertyName; |
| isEmptyAccess = parent; |
| } else if (parent is PrefixedIdentifier) { |
| isEmptyIdentifier = parent.identifier; |
| isEmptyAccess = parent; |
| } |
| |
| if (isEmptyIdentifier == null) { |
| return; |
| } |
| |
| // Should be "isEmpty". |
| Element propertyElement = isEmptyIdentifier.bestElement; |
| if (propertyElement == null || 'isEmpty' != propertyElement.name) { |
| return; |
| } |
| // Should have "isNotEmpty". |
| Element propertyTarget = propertyElement.enclosingElement; |
| if (propertyTarget == null || |
| getChildren(propertyTarget, 'isNotEmpty').isEmpty) { |
| return; |
| } |
| // Should be in PrefixExpression. |
| if (isEmptyAccess.parent is! PrefixExpression) { |
| return; |
| } |
| PrefixExpression prefixExpression = |
| isEmptyAccess.parent as PrefixExpression; |
| // Should be ! |
| if (prefixExpression.operator.type != TokenType.BANG) { |
| return; |
| } |
| |
| rule.reportLint(prefixExpression); |
| } |
| } |