| // Copyright (c) 2020, 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 '../analyzer.dart'; |
| |
| const _desc = r'Avoid calling toString() on runtimeType.'; |
| |
| const _details = r''' |
| |
| Calling `toString` on a runtime type is a non-trivial operation that can |
| negatively impact performance. It's better to avoid it. |
| |
| **BAD:** |
| ``` |
| class A { |
| String toString() => '$runtimeType()'; |
| } |
| ``` |
| |
| **GOOD:** |
| ``` |
| class A { |
| String toString() => 'A()'; |
| } |
| ``` |
| |
| This lint has some exceptions where performance is not a problem or where real |
| type information is more important than performance: |
| |
| * in assertion |
| * in throw expressions |
| * in catch clauses |
| * in mixin declaration |
| * in abstract class |
| |
| '''; |
| |
| class NoRuntimeTypeToString extends LintRule implements NodeLintRule { |
| NoRuntimeTypeToString() |
| : super( |
| name: 'no_runtimeType_toString', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| void registerNodeProcessors(NodeLintRegistry registry, |
| [LinterContext context]) { |
| final visitor = _Visitor(this); |
| registry.addInterpolationExpression(this, visitor); |
| registry.addMethodInvocation(this, visitor); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final LintRule rule; |
| |
| _Visitor(this.rule); |
| |
| @override |
| void visitMethodInvocation(MethodInvocation node) { |
| if (_canSkip(node)) { |
| return; |
| } |
| if (node.methodName.name == 'toString' && |
| _isRuntimeTypeAccess(node.realTarget)) { |
| rule.reportLint(node.methodName); |
| } |
| } |
| |
| @override |
| void visitInterpolationExpression(InterpolationExpression node) { |
| if (_canSkip(node)) { |
| return; |
| } |
| if (_isRuntimeTypeAccess(node.expression)) { |
| rule.reportLint(node.expression); |
| } |
| } |
| |
| bool _isRuntimeTypeAccess(Expression target) => |
| target is PropertyAccess && |
| (target.target is ThisExpression || |
| target.target is SuperExpression) && |
| target.propertyName.name == 'runtimeType' || |
| target is SimpleIdentifier && |
| target.name == 'runtimeType' && |
| target.staticElement is PropertyAccessorElement; |
| |
| bool _canSkip(AstNode node) => |
| node.thisOrAncestorMatching((n) { |
| if (n is Assertion) return true; |
| if (n is ThrowExpression) return true; |
| if (n is CatchClause) return true; |
| if (n is MixinDeclaration) return true; |
| if (n is ClassDeclaration && n.isAbstract) return true; |
| if (n is ExtensionDeclaration) { |
| final extendedElement = n.declaredElement.extendedType.element; |
| return !(extendedElement is ClassElement && |
| !extendedElement.isAbstract); |
| } |
| return false; |
| }) != |
| null; |
| } |