mirror of https://github.com/python/cpython
53 lines
1.4 KiB
Python
53 lines
1.4 KiB
Python
from pegen import grammar
|
|
from pegen.grammar import (
|
|
Alt,
|
|
Cut,
|
|
Gather,
|
|
GrammarVisitor,
|
|
Group,
|
|
Lookahead,
|
|
NamedItem,
|
|
NameLeaf,
|
|
NegativeLookahead,
|
|
Opt,
|
|
PositiveLookahead,
|
|
Repeat0,
|
|
Repeat1,
|
|
Rhs,
|
|
Rule,
|
|
StringLeaf,
|
|
)
|
|
|
|
class ValidationError(Exception):
|
|
pass
|
|
|
|
class GrammarValidator(GrammarVisitor):
|
|
def __init__(self, grammar: grammar.Grammar):
|
|
self.grammar = grammar
|
|
self.rulename = None
|
|
|
|
def validate_rule(self, rulename: str, node: Rule):
|
|
self.rulename = rulename
|
|
self.visit(node)
|
|
self.rulename = None
|
|
|
|
|
|
class SubRuleValidator(GrammarValidator):
|
|
def visit_Rhs(self, node: Rule):
|
|
for index, alt in enumerate(node.alts):
|
|
alts_to_consider = node.alts[index+1:]
|
|
for other_alt in alts_to_consider:
|
|
self.check_intersection(alt, other_alt)
|
|
|
|
def check_intersection(self, first_alt: Alt, second_alt: Alt) -> bool:
|
|
if str(second_alt).startswith(str(first_alt)):
|
|
raise ValidationError(
|
|
f"In {self.rulename} there is an alternative that will "
|
|
f"never be visited:\n{second_alt}")
|
|
|
|
def validate_grammar(the_grammar: grammar.Grammar):
|
|
for validator_cls in GrammarValidator.__subclasses__():
|
|
validator = validator_cls(the_grammar)
|
|
for rule_name, rule in the_grammar.rules.items():
|
|
validator.validate_rule(rule_name, rule)
|