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48f21b3631
The Full Grammar specification in the docs omits rule actions, so grammar rules that raise a syntax error looked like valid syntax.
This was solved in ef940de by hiding those rules in the custom syntax highlighter.
This moves all syntax-error alternatives to invalid rules, adds a validator that ensures that actions containing RAISE_SYNTAX_ERROR are in invalid rules, and reverts the syntax highlighter hack.
53 lines
1.8 KiB
Python
53 lines
1.8 KiB
Python
from typing import Optional
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from pegen import grammar
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from pegen.grammar import Alt, GrammarVisitor, Rhs, Rule
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class ValidationError(Exception):
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pass
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class GrammarValidator(GrammarVisitor):
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def __init__(self, grammar: grammar.Grammar) -> None:
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self.grammar = grammar
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self.rulename: Optional[str] = None
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def validate_rule(self, rulename: str, node: Rule) -> None:
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self.rulename = rulename
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self.visit(node)
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self.rulename = None
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class SubRuleValidator(GrammarValidator):
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def visit_Rhs(self, node: Rhs) -> None:
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for index, alt in enumerate(node.alts):
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alts_to_consider = node.alts[index + 1 :]
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for other_alt in alts_to_consider:
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self.check_intersection(alt, other_alt)
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def check_intersection(self, first_alt: Alt, second_alt: Alt) -> None:
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if str(second_alt).startswith(str(first_alt)):
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raise ValidationError(
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f"In {self.rulename} there is an alternative that will "
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f"never be visited:\n{second_alt}"
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)
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class RaiseRuleValidator(GrammarValidator):
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def visit_Alt(self, node: Alt) -> None:
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if self.rulename and self.rulename.startswith('invalid'):
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# raising is allowed in invalid rules
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return
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if node.action and 'RAISE_SYNTAX_ERROR' in node.action:
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raise ValidationError(
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f"In {self.rulename!r} there is an alternative that contains "
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f"RAISE_SYNTAX_ERROR; this is only allowed in invalid_ rules"
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)
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def validate_grammar(the_grammar: grammar.Grammar) -> None:
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for validator_cls in GrammarValidator.__subclasses__():
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validator = validator_cls(the_grammar)
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for rule_name, rule in the_grammar.rules.items():
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validator.validate_rule(rule_name, rule)
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