| // 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 'dart:collection'; |
| |
| 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/element.dart'; |
| |
| import '../analyzer.dart'; |
| import '../util/dart_type_utilities.dart'; |
| |
| const _desc = r'Private field could be final.'; |
| |
| const _details = r''' |
| |
| **DO** prefer declaring private fields as final if they are not reassigned later |
| in the library. |
| |
| Declaring fields as final when possible is a good practice because it helps |
| avoid accidental reassignments and allows the compiler to do optimizations. |
| |
| **BAD:** |
| ```dart |
| class BadImmutable { |
| var _label = 'hola mundo! BadImmutable'; // LINT |
| var label = 'hola mundo! BadImmutable'; // OK |
| } |
| ``` |
| |
| **BAD:** |
| ```dart |
| class MultipleMutable { |
| var _label = 'hola mundo! GoodMutable', _offender = 'mumble mumble!'; // LINT |
| var _someOther; // LINT |
| |
| MultipleMutable() : _someOther = 5; |
| |
| MultipleMutable(this._someOther); |
| |
| void changeLabel() { |
| _label= 'hello world! GoodMutable'; |
| } |
| } |
| ``` |
| |
| **GOOD:** |
| ```dart |
| class GoodImmutable { |
| final label = 'hola mundo! BadImmutable', bla = 5; // OK |
| final _label = 'hola mundo! BadImmutable', _bla = 5; // OK |
| } |
| ``` |
| |
| **GOOD:** |
| ```dart |
| class GoodMutable { |
| var _label = 'hola mundo! GoodMutable'; |
| |
| void changeLabel() { |
| _label = 'hello world! GoodMutable'; |
| } |
| } |
| ``` |
| |
| **BAD:** |
| ```dart |
| class AssignedInAllConstructors { |
| var _label; // LINT |
| AssignedInAllConstructors(this._label); |
| AssignedInAllConstructors.withDefault() : _label = 'Hello'; |
| } |
| ``` |
| |
| **GOOD:** |
| ```dart |
| class NotAssignedInAllConstructors { |
| var _label; // OK |
| NotAssignedInAllConstructors(); |
| NotAssignedInAllConstructors.withDefault() : _label = 'Hello'; |
| } |
| ``` |
| '''; |
| |
| bool _containedInFormal(Element element, FormalParameter formal) { |
| var formalField = formal.identifier?.staticElement; |
| return formalField is FieldFormalParameterElement && |
| formalField.field == element; |
| } |
| |
| bool _containedInInitializer( |
| Element element, ConstructorInitializer initializer) => |
| initializer is ConstructorFieldInitializer && |
| DartTypeUtilities.getCanonicalElementFromIdentifier( |
| initializer.fieldName) == |
| element; |
| |
| class PreferFinalFields extends LintRule implements NodeLintRule { |
| PreferFinalFields() |
| : super( |
| name: 'prefer_final_fields', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| var visitor = _Visitor(this); |
| registry.addCompilationUnit(this, visitor); |
| registry.addFieldDeclaration(this, visitor); |
| } |
| } |
| |
| class _MutatedFieldsCollector extends RecursiveAstVisitor<void> { |
| final Set<FieldElement> _mutatedFields; |
| |
| _MutatedFieldsCollector(this._mutatedFields); |
| |
| @override |
| void visitAssignmentExpression(AssignmentExpression node) { |
| _addMutatedFieldElement(node); |
| super.visitAssignmentExpression(node); |
| } |
| |
| @override |
| void visitPostfixExpression(PostfixExpression node) { |
| _addMutatedFieldElement(node); |
| super.visitPostfixExpression(node); |
| } |
| |
| @override |
| void visitPrefixExpression(PrefixExpression node) { |
| var operator = node.operator; |
| if (operator.type == TokenType.MINUS_MINUS || |
| operator.type == TokenType.PLUS_PLUS) { |
| _addMutatedFieldElement(node); |
| } |
| super.visitPrefixExpression(node); |
| } |
| |
| void _addMutatedFieldElement(CompoundAssignmentExpression assignment) { |
| var element = |
| DartTypeUtilities.getCanonicalElement(assignment.writeElement); |
| if (element is FieldElement) { |
| _mutatedFields.add(element); |
| } |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final LintRule rule; |
| |
| final Set<FieldElement> _mutatedFields = HashSet<FieldElement>(); |
| |
| _Visitor(this.rule); |
| |
| @override |
| void visitCompilationUnit(CompilationUnit node) { |
| node.accept(_MutatedFieldsCollector(_mutatedFields)); |
| } |
| |
| @override |
| void visitFieldDeclaration(FieldDeclaration node) { |
| var fields = node.fields; |
| if (fields.isFinal || fields.isConst) { |
| return; |
| } |
| |
| for (var variable in fields.variables) { |
| var element = variable.declaredElement; |
| |
| if (element is PropertyInducingElement && |
| element.isPrivate && |
| !_mutatedFields.contains(element)) { |
| bool fieldInConstructor(ConstructorDeclaration constructor) => |
| constructor.initializers.any((ConstructorInitializer initializer) => |
| _containedInInitializer(element, initializer)) || |
| constructor.parameters.parameters.any((FormalParameter formal) => |
| _containedInFormal(element, formal)); |
| |
| var classDeclaration = node.parent; |
| var constructors = classDeclaration is ClassDeclaration |
| ? classDeclaration.members.whereType<ConstructorDeclaration>() |
| : <ConstructorDeclaration>[]; |
| var isFieldInConstructors = constructors.any(fieldInConstructor); |
| var isFieldInAllConstructors = constructors.every(fieldInConstructor); |
| |
| if (isFieldInConstructors) { |
| if (isFieldInAllConstructors) { |
| rule.reportLint(variable); |
| } |
| } else if (element.hasInitializer) { |
| rule.reportLint(variable); |
| } |
| } |
| } |
| } |
| } |