| // 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 PrefixExpression, PrefixedIdentifier, PropertyAccess, SimpleIdentifier; |
| import 'package:analyzer/dart/ast/token.dart'; |
| import 'package:analyzer/dart/ast/visitor.dart'; |
| |
| import '../analyzer.dart'; |
| import '../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:** |
| ```dart |
| if (todo.isNotEmpty) { |
| sendResults(request, todo.isEmpty); |
| } |
| ``` |
| |
| **BAD:** |
| ```dart |
| if (!sources.isEmpty) { |
| process(sources); |
| } |
| ``` |
| |
| '''; |
| |
| class PreferIsNotEmpty extends LintRule implements NodeLintRule { |
| PreferIsNotEmpty() |
| : super( |
| name: 'prefer_is_not_empty', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| var visitor = _Visitor(this); |
| registry.addPrefixExpression(this, visitor); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final LintRule rule; |
| |
| _Visitor(this.rule); |
| |
| @override |
| void visitPrefixExpression(PrefixExpression node) { |
| // Should be prefixed w/ a "!". |
| var prefix = node.operator; |
| if (prefix.type != TokenType.BANG) { |
| return; |
| } |
| |
| var expression = node.operand.unParenthesized; |
| |
| // Should be a property access or prefixed identifier. |
| SimpleIdentifier? isEmptyIdentifier; |
| if (expression is PropertyAccess) { |
| isEmptyIdentifier = expression.propertyName; |
| } else if (expression is PrefixedIdentifier) { |
| isEmptyIdentifier = expression.identifier; |
| } |
| if (isEmptyIdentifier == null) { |
| return; |
| } |
| |
| // Element identifier should be "isEmpty". |
| var propertyElement = isEmptyIdentifier.staticElement; |
| if (propertyElement == null || 'isEmpty' != propertyElement.name) { |
| return; |
| } |
| |
| // Element should also support "isNotEmpty". |
| var propertyTarget = propertyElement.enclosingElement; |
| if (propertyTarget == null || |
| getChildren(propertyTarget, 'isNotEmpty').isEmpty) { |
| return; |
| } |
| |
| rule.reportLint(node); |
| } |
| } |