| // 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:linter/src/analyzer.dart'; |
| |
| const _desc = r'Boolean expression composed only with literals.'; |
| |
| const _details = r''' |
| |
| **DON'T** test for conditions composed only by literals, since the value can be |
| inferred at compile time. |
| |
| Conditional statements using a condition which cannot be anything but FALSE have |
| the effect of making blocks of code non-functional. If the condition cannot |
| evaluate to anything but `true`, the conditional statement is completely |
| redundant, and makes the code less readable. |
| It is quite likely that the code does not match the programmer's intent. |
| Either the condition should be removed or it should be updated so that it does |
| not always evaluate to `true` or `false`. |
| |
| **BAD:** |
| ``` |
| void bad() { |
| if (true) {} // LINT |
| } |
| ``` |
| |
| **BAD:** |
| ``` |
| void bad() { |
| if (true && 1 != 0) {} // LINT |
| } |
| ``` |
| |
| **BAD:** |
| ``` |
| void bad() { |
| if (1 != 0 && true) {} // LINT |
| } |
| ``` |
| |
| **BAD:** |
| ``` |
| void bad() { |
| if (1 < 0 && true) {} // LINT |
| } |
| ``` |
| |
| **BAD:** |
| ``` |
| void bad() { |
| if (true && false) {} // LINT |
| } |
| ``` |
| |
| **BAD:** |
| ``` |
| void bad() { |
| if (1 != 0) {} // LINT |
| } |
| ``` |
| |
| **BAD:** |
| ``` |
| void bad() { |
| if (true && 1 != 0 || 3 < 4) {} // LINT |
| } |
| ``` |
| |
| **BAD:** |
| ``` |
| void bad() { |
| if (1 != 0 || 3 < 4 && true) {} // LINT |
| } |
| ``` |
| |
| '''; |
| |
| bool _onlyLiterals(Expression rawExpression) { |
| final expression = rawExpression?.unParenthesized; |
| if (expression is Literal) { |
| return true; |
| } |
| if (expression is PrefixExpression) { |
| return _onlyLiterals(expression.operand); |
| } |
| if (expression is BinaryExpression) { |
| if (expression.operator.type == TokenType.QUESTION_QUESTION) { |
| return _onlyLiterals(expression.leftOperand); |
| } |
| return _onlyLiterals(expression.leftOperand) && |
| _onlyLiterals(expression.rightOperand); |
| } |
| return false; |
| } |
| |
| class LiteralOnlyBooleanExpressions extends LintRule implements NodeLintRule { |
| LiteralOnlyBooleanExpressions() |
| : super( |
| name: 'literal_only_boolean_expressions', |
| description: _desc, |
| details: _details, |
| group: Group.errors); |
| |
| @override |
| void registerNodeProcessors(NodeLintRegistry registry, |
| [LinterContext context]) { |
| final visitor = new _Visitor(this); |
| registry.addDoStatement(this, visitor); |
| registry.addForStatement2(this, visitor); |
| registry.addIfStatement(this, visitor); |
| registry.addWhileStatement(this, visitor); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final LintRule rule; |
| |
| _Visitor(this.rule); |
| |
| @override |
| void visitDoStatement(DoStatement node) { |
| if (_onlyLiterals(node.condition)) { |
| rule.reportLint(node); |
| } |
| } |
| |
| @override |
| void visitForStatement2(ForStatement2 node) { |
| final loopParts = node.forLoopParts; |
| if (loopParts is ForParts) { |
| if (_onlyLiterals(loopParts.condition)) { |
| rule.reportLint(node); |
| } |
| } |
| } |
| |
| @override |
| void visitIfStatement(IfStatement node) { |
| if (_onlyLiterals(node.condition)) { |
| rule.reportLint(node); |
| } |
| } |
| |
| @override |
| void visitWhileStatement(WhileStatement node) { |
| if (_onlyLiterals(node.condition)) { |
| rule.reportLint(node); |
| } |
| } |
| } |