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60 lines
1.0 KiB
JavaScript
60 lines
1.0 KiB
JavaScript
"use strict";
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const visitor = require( "../visitor" );
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// Removes proxy rules -- that is, rules that only delegate to other rule.
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function removeProxyRules( ast, options ) {
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function isProxyRule( node ) {
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return node.type === "rule" && node.expression.type === "rule_ref";
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}
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function replaceRuleRefs( ast, from, to ) {
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const replace = visitor.build( {
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rule_ref( node ) {
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if ( node.name === from ) {
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node.name = to;
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}
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}
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} );
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replace( ast );
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}
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const indices = [];
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ast.rules.forEach( ( rule, i ) => {
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if ( isProxyRule( rule ) ) {
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replaceRuleRefs( ast, rule.name, rule.expression.name );
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if ( options.allowedStartRules.indexOf( rule.name ) === -1 ) {
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indices.push( i );
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}
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}
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} );
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indices.reverse();
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indices.forEach( i => {
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ast.rules.splice( i, 1 );
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} );
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}
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module.exports = removeProxyRules;
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