| // 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 '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'Cascade consecutive method invocations on the same reference.'; |
| |
| const _details = r''' |
| |
| **DO** Use the cascading style when succesively invoking methods on the same |
| reference. |
| |
| **BAD:** |
| ``` |
| SomeClass someReference = SomeClass(); |
| someReference.firstMethod(); |
| someReference.secondMethod(); |
| ``` |
| |
| **BAD:** |
| ``` |
| SomeClass someReference = SomeClass(); |
| ... |
| someReference.firstMethod(); |
| someReference.aProperty = value; |
| someReference.secondMethod(); |
| ``` |
| |
| **GOOD:** |
| ``` |
| SomeClass someReference = SomeClass() |
| ..firstMethod() |
| ..aProperty = value |
| ..secondMethod(); |
| ``` |
| |
| **GOOD:** |
| ``` |
| SomeClass someReference = SomeClass(); |
| ... |
| someReference |
| ..firstMethod() |
| ..aProperty = value |
| ..secondMethod(); |
| ``` |
| |
| '''; |
| |
| Element _getElementFromVariableDeclarationStatement( |
| VariableDeclarationStatement statement) { |
| final variables = statement.variables.variables; |
| if (variables.length == 1) { |
| var variable = variables.single; |
| if (variable.initializer is AwaitExpression) { |
| // `await` has a higher precedence than a cascade, but because the token |
| // `await` is followed by whitespace, it may look like the cascade binds |
| // tighter, for example in `await Future.value([1,2,3])..forEach(print)`. |
| // |
| // In such a case, we should not return any cascadable element here. |
| return null; |
| } |
| return variable.declaredElement; |
| } |
| return null; |
| } |
| |
| ExecutableElement _getExecutableElementFromMethodInvocation( |
| MethodInvocation node) { |
| if (_isInvokedWithoutNullAwareOperator(node.operator)) { |
| final executableElement = |
| DartTypeUtilities.getCanonicalElementFromIdentifier(node.methodName); |
| if (executableElement is ExecutableElement) { |
| return executableElement; |
| } |
| } |
| return null; |
| } |
| |
| Element _getPrefixElementFromExpression(Expression rawExpression) { |
| final expression = rawExpression.unParenthesized; |
| if (expression is PrefixedIdentifier) { |
| return DartTypeUtilities.getCanonicalElementFromIdentifier( |
| expression.prefix); |
| } else if (expression is PropertyAccess && |
| _isInvokedWithoutNullAwareOperator(expression.operator) && |
| expression.target is SimpleIdentifier) { |
| return DartTypeUtilities.getCanonicalElementFromIdentifier( |
| expression.target); |
| } |
| return null; |
| } |
| |
| Element _getTargetElementFromCascadeExpression(CascadeExpression node) => |
| DartTypeUtilities.getCanonicalElementFromIdentifier(node.target); |
| |
| Element _getTargetElementFromMethodInvocation(MethodInvocation node) => |
| DartTypeUtilities.getCanonicalElementFromIdentifier(node.target); |
| |
| bool _isInvokedWithoutNullAwareOperator(Token token) => |
| token?.type == TokenType.PERIOD; |
| |
| /// Rule to lint consecutive invocations of methods or getters on the same |
| /// reference that could be done with the cascade operator. |
| class CascadeInvocations extends LintRule implements NodeLintRule { |
| /// Default constructor. |
| CascadeInvocations() |
| : super( |
| name: 'cascade_invocations', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| final visitor = _Visitor(this); |
| registry.addBlock(this, visitor); |
| } |
| } |
| |
| /// A CascadableExpression is an object that is built from an expression and |
| /// knows if it is able to join to another CascadableExpression. |
| class _CascadableExpression { |
| static final NULL_CASCADABLE_EXPRESSION = _CascadableExpression._internal( |
| null, [], |
| canJoin: false, canReceive: false, canBeCascaded: false); |
| |
| /// Whether this expression can be joined with a previous expression via a |
| /// cascade operation. |
| final bool canJoin; |
| |
| /// Whether this expression can receive an additional expression with a |
| /// cascade operation. |
| /// |
| /// For example, `a.b = 1` can receive, but `a = 1` cannot receive. |
| final bool canReceive; |
| final bool canBeCascaded; |
| |
| /// This is necessary when you have a variable declaration so that element |
| /// is critical and it can't be used as a parameter of a method invocation or |
| /// in the right part of an assignment in a following expression that we would |
| /// like to join to this. |
| final bool isCritical; |
| final Element element; |
| final List<AstNode> criticalNodes; |
| |
| factory _CascadableExpression.fromExpressionStatement( |
| ExpressionStatement statement) { |
| final expression = statement.expression.unParenthesized; |
| if (expression is AssignmentExpression) { |
| return _CascadableExpression._fromAssignmentExpression(expression); |
| } |
| if (expression is MethodInvocation) { |
| return _CascadableExpression._fromMethodInvocation(expression); |
| } |
| if (expression is CascadeExpression) { |
| return _CascadableExpression._fromCascadeExpression(expression); |
| } |
| if (expression is PropertyAccess && |
| _isInvokedWithoutNullAwareOperator(expression.operator)) { |
| return _CascadableExpression._fromPropertyAccess(expression); |
| } |
| if (expression is PrefixedIdentifier) { |
| return _CascadableExpression._fromPrefixedIdentifier(expression); |
| } |
| return NULL_CASCADABLE_EXPRESSION; |
| } |
| |
| factory _CascadableExpression.fromVariableDeclarationStatement( |
| VariableDeclarationStatement node) { |
| final element = _getElementFromVariableDeclarationStatement(node); |
| return _CascadableExpression._internal(element, [], |
| canJoin: false, |
| canReceive: true, |
| canBeCascaded: false, |
| isCritical: true); |
| } |
| |
| factory _CascadableExpression._fromAssignmentExpression( |
| AssignmentExpression node) { |
| final leftExpression = node.leftHandSide.unParenthesized; |
| if (leftExpression is SimpleIdentifier) { |
| return _CascadableExpression._internal( |
| DartTypeUtilities.getCanonicalElement(leftExpression.staticElement), |
| [node.rightHandSide], |
| canJoin: false, |
| canReceive: node.operator.type != TokenType.QUESTION_QUESTION_EQ, |
| canBeCascaded: false, |
| isCritical: true); |
| } |
| // setters |
| final variable = _getPrefixElementFromExpression(leftExpression); |
| final canReceive = node.operator.type != TokenType.QUESTION_QUESTION_EQ && |
| variable is VariableElement && |
| !variable.isStatic; |
| return _CascadableExpression._internal(variable, [node.rightHandSide], |
| canJoin: true, canReceive: canReceive, canBeCascaded: true); |
| } |
| |
| factory _CascadableExpression._fromCascadeExpression( |
| CascadeExpression node) => |
| _CascadableExpression._internal( |
| _getTargetElementFromCascadeExpression(node), node.cascadeSections, |
| canJoin: true, canReceive: true, canBeCascaded: true); |
| |
| factory _CascadableExpression._fromMethodInvocation(MethodInvocation node) { |
| final executableElement = _getExecutableElementFromMethodInvocation(node); |
| final isNonStatic = executableElement?.isStatic == false; |
| if (isNonStatic) { |
| final isSimpleIdentifier = node.target is SimpleIdentifier; |
| return _CascadableExpression._internal( |
| _getTargetElementFromMethodInvocation(node), [node.argumentList], |
| canJoin: isSimpleIdentifier, |
| canReceive: isSimpleIdentifier, |
| canBeCascaded: true); |
| } |
| return NULL_CASCADABLE_EXPRESSION; |
| } |
| |
| factory _CascadableExpression._fromPrefixedIdentifier( |
| PrefixedIdentifier node) => |
| _CascadableExpression._internal( |
| DartTypeUtilities.getCanonicalElementFromIdentifier(node.prefix), [], |
| canJoin: true, canReceive: true, canBeCascaded: true); |
| |
| factory _CascadableExpression._fromPropertyAccess(PropertyAccess node) { |
| var targetIsSimple = node.target is SimpleIdentifier; |
| return _CascadableExpression._internal( |
| DartTypeUtilities.getCanonicalElementFromIdentifier(node.target), [], |
| // If the target is something like `(a + b).x`, then node can neither |
| // join, nor receive. |
| // |
| // This restriction is quite limiting. It means that this rule cannot |
| // report on the following code: |
| // |
| // b1.a |
| // ..f = 1 |
| // ..g = 1; |
| // b2.a.f = 2; // Could report here. |
| // |
| // But it may be difficult to accurately know if complicated |
| // expressions are cascadable. Just because two expressions are "equal" |
| // or look the same, does not mean they can be cascaded; for example: |
| // |
| // (b1 + b2).a |
| // ..f = 1 |
| // ..g = 1; |
| // (b1 + b2).a.f = 2; // Should not report here. |
| // |
| // TODO(srawlins): Refactor this lint rule to use |
| // DartTypeUtilities.canonicalElementsFromIdentifiersAreEqual(), which |
| // should fix this issue. |
| canJoin: targetIsSimple, |
| canReceive: targetIsSimple, |
| canBeCascaded: true); |
| } |
| |
| _CascadableExpression._internal(this.element, this.criticalNodes, |
| {this.canJoin, |
| this.canReceive, |
| this.canBeCascaded, |
| this.isCritical = false}); |
| |
| /// Whether `this` is compatible to be joined with [expressionBox] with a |
| /// cascade operation. |
| bool compatibleWith(_CascadableExpression expressionBox) => |
| element != null && |
| expressionBox.canReceive && |
| canJoin && |
| (canBeCascaded || expressionBox.canBeCascaded) && |
| element == expressionBox.element && |
| !_hasCriticalDependencies(expressionBox); |
| |
| bool _hasCriticalDependencies(_CascadableExpression expressionBox) { |
| bool _isCriticalNode(AstNode node) => |
| DartTypeUtilities.getCanonicalElementFromIdentifier(node) == |
| expressionBox.element; |
| return expressionBox.isCritical && |
| criticalNodes.any((node) => |
| _isCriticalNode(node) || |
| DartTypeUtilities.traverseNodesInDFS(node).any(_isCriticalNode)); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final LintRule rule; |
| |
| _Visitor(this.rule); |
| |
| @override |
| void visitBlock(Block node) { |
| if (node.statements.length < 2) { |
| return; |
| } |
| var previousExpressionBox = |
| _CascadableExpression.NULL_CASCADABLE_EXPRESSION; |
| for (final statement in node.statements) { |
| var currentExpressionBox = |
| _CascadableExpression.NULL_CASCADABLE_EXPRESSION; |
| if (statement is VariableDeclarationStatement) { |
| currentExpressionBox = |
| _CascadableExpression.fromVariableDeclarationStatement(statement); |
| } |
| if (statement is ExpressionStatement) { |
| currentExpressionBox = |
| _CascadableExpression.fromExpressionStatement(statement); |
| } |
| if (currentExpressionBox.compatibleWith(previousExpressionBox)) { |
| rule.reportLint(statement); |
| } |
| previousExpressionBox = currentExpressionBox; |
| } |
| } |
| } |