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Meta: Optimize keyword alternatives parsing

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Callum Law 2026-05-01 13:24:02 +12:00 committed by Sam Atkins
parent f578d95be0
commit b39bcaf1e4
1 changed files with 14 additions and 0 deletions
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14
Meta/Utils/CSSGrammar/generator.py
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@ -69,12 +69,26 @@ def generate_css_parser_expression_for_alternatives(
) -> None:
out.write(f"auto const parse_{cpp_name}_alternatives = [&]() -> RefPtr<StyleValue const> {{\n")
# NB: As an optimization we combine all keyword alternatives into a single parse_specific_keyword_value call to
# avoid unnecessary backtracking in the common case of multiple keyword alternatives.
keyword_alternatives: list[str] = []
for i, alternative in enumerate(alternatives):
if isinstance(alternative, ComponentValueGrammarNode) and isinstance(alternative.component_value, Keyword):
keyword_alternatives.append(alternative.component_value.value)
continue
alternative_name = f"{cpp_name}_alternative_{i}"
generate_css_parser_expression_for_grammar_node(out, alternative_name, alternative)
out.write(f"""if ({alternative_name})
return {alternative_name};
""")
if keyword_alternatives:
keyword_alternatives_names = ", ".join(f"Keyword::{title_casify(keyword)}" for keyword in keyword_alternatives)
out.write(f"""auto {cpp_name}_keyword_alternative = parse_specific_keyword_value(tokens, {{ {{ {keyword_alternatives_names} }} }});
if ({cpp_name}_keyword_alternative)
return {cpp_name}_keyword_alternative;
""")
out.write(f"""return nullptr;