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| 1 // Copyright (c) 2015, the Dart project authors. Please see the AUTHORS file | |
| 2 // for details. All rights reserved. Use of this source code is governed by a | |
| 3 // BSD-style license that can be found in the LICENSE file. | |
| 4 | |
| 5 import 'package:source_span/source_span.dart'; | |
| 6 | |
| 7 import 'ast.dart'; | |
| 8 import 'scanner.dart'; | |
| 9 import 'token.dart'; | |
| 10 | |
| 11 /// A class for parsing a platform selector. | |
| 12 /// | |
| 13 /// Platform selectors use a stripped-down version of the Dart expression | |
| 14 /// syntax that only contains variables, parentheses, and boolean operators. | |
| 15 /// Variables may also contain dashes, contrary to Dart's syntax; this allows | |
| 16 /// consistency with command-line arguments. | |
| 17 class Parser { | |
| 18 /// The scanner that tokenizes the selector. | |
| 19 final Scanner _scanner; | |
| 20 | |
| 21 Parser(String selector) | |
| 22 : _scanner = new Scanner(selector); | |
| 23 | |
| 24 /// Parses the selector. | |
| 25 /// | |
| 26 /// This must only be called once per parser. | |
| 27 Node parse() { | |
| 28 var selector = _conditional(); | |
| 29 | |
| 30 if (_scanner.peek().type != TokenType.endOfFile) { | |
| 31 throw new SourceSpanFormatException( | |
| 32 "Expected end of input.", _scanner.peek().span); | |
| 33 } | |
| 34 | |
| 35 return selector; | |
| 36 } | |
| 37 | |
| 38 /// Parses a conditional: | |
| 39 /// | |
| 40 /// conditionalExpression: | |
| 41 /// logicalOrExpression ("?" conditionalExpression ":" | |
| 42 /// conditionalExpression)? | |
| 43 Node _conditional() { | |
| 44 var condition = _or(); | |
| 45 if (!_scanner.scan(TokenType.questionMark)) return condition; | |
| 46 | |
| 47 var whenTrue = _conditional(); | |
| 48 if (!_scanner.scan(TokenType.colon)) { | |
| 49 throw new SourceSpanFormatException( | |
| 50 'Expected ":".', _scanner.peek().span); | |
| 51 } | |
| 52 | |
| 53 var whenFalse = _conditional(); | |
| 54 return new ConditionalNode(condition, whenTrue, whenFalse); | |
| 55 } | |
| 56 | |
| 57 /// Parses a logical or: | |
| 58 /// | |
| 59 /// logicalOrExpression: | |
| 60 /// logicalAndExpression ("||" logicalOrExpression)? | |
| 61 Node _or() { | |
| 62 var left = _and(); | |
| 63 if (!_scanner.scan(TokenType.or)) return left; | |
| 64 return new OrNode(left, _or()); | |
| 65 } | |
| 66 | |
| 67 /// Parses a logical and: | |
| 68 /// | |
| 69 /// logicalAndExpression: | |
| 70 /// simpleExpression ("&&" logicalAndExpression)? | |
| 71 Node _and() { | |
| 72 var left = _simpleExpression(); | |
| 73 if (!_scanner.scan(TokenType.and)) return left; | |
| 74 return new AndNode(left, _and()); | |
| 75 } | |
| 76 | |
| 77 /// Parses a simple expression: | |
| 78 /// | |
| 79 /// simpleExpression: | |
| 80 /// "!" simpleExpression | | |
| 81 /// "(" conditionalExpression ")" | | |
| 82 /// IDENTIFIER | |
| 83 Node _simpleExpression() { | |
| 84 var token = _scanner.next(); | |
| 85 switch (token.type) { | |
| 86 case TokenType.not: | |
| 87 var child = _simpleExpression(); | |
| 88 return new NotNode(child, token.span.expand(child.span)); | |
| 89 | |
| 90 case TokenType.leftParen: | |
| 91 var child = _conditional(); | |
| 92 if (!_scanner.scan(TokenType.rightParen)) { | |
| 93 throw new SourceSpanFormatException( | |
| 94 'Expected ")".', _scanner.peek().span); | |
| 95 } | |
| 96 return child; | |
| 97 | |
| 98 case TokenType.identifier: | |
| 99 return new VariableNode(token.name, token.span); | |
| 100 | |
| 101 default: | |
| 102 throw new SourceSpanFormatException("Expected expression.", token.span); | |
| 103 } | |
| 104 } | |
| 105 } | |
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Chromium Code Reviews
Issue 1717483002:
Make PlatformSelector use boolean_selector. (Closed)
Base URL: git@github.com:dart-lang/test@master