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pegjs/lib/compiler/passes/remove-proxy-rules.js

43 lines
845 B
JavaScript

"use strict";
// Removes proxy rules -- that is, rules that only delegate to other rule.
function removeProxyRules( ast, session, options ) {
function isProxyRule( node ) {
return node.type === "rule" && node.expression.type === "rule_ref";
}
const replaceRuleRefs = session.buildVisitor( {
rule_ref( node, proxy, real ) {
if ( node.name === proxy ) node.name = real;
}
} );
const allowedStartRules = options.allowedStartRules;
const rules = [];
for ( const rule of ast.rules ) {
if ( isProxyRule( rule ) ) {
replaceRuleRefs( ast, rule.name, rule.expression.name );
if ( allowedStartRules.indexOf( rule.name ) < 0 ) continue;
}
rules.push( rule );
}
ast.rules = rules;
}
module.exports = removeProxyRules;