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To do this we parse the grammar supplied in `ValueTypes.json` and generate the appropriate parsing function in `CSS::Parser::Parser` Only a small subset of the CSS grammar (i.e. types `<foo>` and alternatives `<foo> | <bar>`) is implemented so far, it will be expanded in later commits.
62 lines
2.1 KiB
Python
62 lines
2.1 KiB
Python
from Utils.CSSGrammar.Parser.grammar_node import CombinatorGrammarNode
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from Utils.CSSGrammar.Parser.grammar_node import CombinatorType
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from Utils.CSSGrammar.Parser.grammar_node import ComponentValueGrammarNode
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from Utils.CSSGrammar.Parser.grammar_node import GrammarNode
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from Utils.CSSGrammar.Parser.token import Token
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from Utils.CSSGrammar.Parser.token import TokenType
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from Utils.CSSGrammar.Parser.tokenizer import Tokenizer
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class Parser:
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def __init__(self, tokens: list[Token]) -> None:
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self.tokens = tokens
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self.index = 0
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@classmethod
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def parse_value_definition_grammar(cls, input: str) -> GrammarNode:
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parser = cls(Tokenizer.tokenize(input))
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value = parser.parse_alternatives()
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if not parser.peek().is_token_type(TokenType.END_OF_FILE):
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raise SyntaxError("CSSGrammar::Parser: Unexpected trailing input")
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return value
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def parse_alternatives(self) -> GrammarNode:
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children = [self.parse_component_value()]
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while self.peek().is_token_type(TokenType.SINGLE_BAR):
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self.consume()
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children.append(self.parse_component_value())
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if len(children) == 1:
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return children[0]
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return CombinatorGrammarNode(CombinatorType.ALTERNATIVES, children)
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def parse_component_value(self) -> GrammarNode:
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# https://drafts.csswg.org/css-values-4/#component-multipliers
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# FIXME: Support component multipliers
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if not self.peek().is_token_type(TokenType.COMPONENT_VALUE):
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raise SyntaxError("CSSGrammar::Parser: Expected a component value")
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return ComponentValueGrammarNode(self.consume().component_value())
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def peek(self, offset: int = 0) -> Token:
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index = min(self.index + offset, len(self.tokens) - 1)
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return self.tokens[index]
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def consume(self) -> Token:
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token = self.peek()
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if not token.is_token_type(TokenType.END_OF_FILE):
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self.index += 1
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return token
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def parse_value_definition_grammar(input: str) -> GrammarNode:
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return Parser.parse_value_definition_grammar(input)
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