| // 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/visitor.dart'; |
| import 'package:analyzer/dart/element/type.dart'; |
| |
| import '../analyzer.dart'; |
| import '../util/dart_type_utilities.dart'; |
| |
| const _desc = |
| r'Avoid returning this from methods just to enable a fluent interface.'; |
| |
| const _details = r''' |
| |
| **AVOID** returning this from methods just to enable a fluent interface. |
| |
| Returning `this` from a method is redundant; Dart has a cascade operator which |
| allows method chaining universally. |
| |
| Returning `this` is allowed for: |
| |
| - operators |
| - methods with a return type different of the current class |
| - methods defined in parent classes / mixins or interfaces |
| - methods defined in extensions |
| |
| **BAD:** |
| ```dart |
| var buffer = StringBuffer() |
| .write('one') |
| .write('two') |
| .write('three'); |
| ``` |
| |
| **GOOD:** |
| ```dart |
| var buffer = StringBuffer() |
| ..write('one') |
| ..write('two') |
| ..write('three'); |
| ``` |
| |
| '''; |
| |
| bool _isFunctionExpression(AstNode node) => node is FunctionExpression; |
| |
| bool _isReturnStatement(AstNode node) => node is ReturnStatement; |
| |
| bool _returnsThis(AstNode node) => |
| (node as ReturnStatement).expression is ThisExpression; |
| |
| class AvoidReturningThis extends LintRule implements NodeLintRule { |
| AvoidReturningThis() |
| : super( |
| name: 'avoid_returning_this', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| var visitor = _Visitor(this); |
| registry.addMethodDeclaration(this, visitor); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final LintRule rule; |
| |
| _Visitor(this.rule); |
| |
| @override |
| void visitMethodDeclaration(MethodDeclaration node) { |
| if (node.isOperator) return; |
| |
| var parent = node.parent; |
| if (parent is ClassOrMixinDeclaration) { |
| if (DartTypeUtilities.overridesMethod(node)) { |
| return; |
| } |
| |
| var returnType = node.declaredElement?.returnType; |
| if (returnType is InterfaceType && |
| returnType.element == parent.declaredElement) { |
| } else { |
| return; |
| } |
| } else { |
| // Ignore Extensions. |
| return; |
| } |
| |
| var body = node.body; |
| if (body is BlockFunctionBody) { |
| var returnStatements = DartTypeUtilities.traverseNodesInDFS(body.block, |
| excludeCriteria: _isFunctionExpression) |
| .where(_isReturnStatement); |
| if (returnStatements.isNotEmpty && returnStatements.every(_returnsThis)) { |
| rule.reportLint(node.name); |
| } |
| } else if (body is ExpressionFunctionBody) { |
| if (body.expression is ThisExpression) { |
| rule.reportLint(node.name); |
| } |
| } |
| } |
| } |