5e146fce38
Implement a new syntax to extract matched strings from expressions. For
example, instead of:
identifier = first:[a-zA-Z_] rest:[a-zA-Z0-9_]* { return first + rest.join(""); }
you can now just write:
identifier = $([a-zA-Z_] [a-zA-Z0-9_]*)
This is useful mostly for "lexical" rules at the bottom of many
grammars.
Note that structured match results are still built for the expressions
prefixed by "$", they are just ignored. I plan to optimize this later
(sometime after the code generator rewrite).
76 lines
1.9 KiB
JavaScript
76 lines
1.9 KiB
JavaScript
var utils = require("../../utils");
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/*
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* Removes proxy rules -- that is, rules that only delegate to other rule.
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*/
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module.exports = function(ast) {
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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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function nop() {}
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function replaceInExpression(node, from, to) {
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replace(node.expression, from, to);
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}
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function replaceInSubnodes(propertyName) {
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return function(node, from, to) {
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utils.each(node[propertyName], function(subnode) {
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replace(subnode, from, to);
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});
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};
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}
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var replace = utils.buildNodeVisitor({
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grammar: replaceInSubnodes("rules"),
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rule: replaceInExpression,
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named: replaceInExpression,
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choice: replaceInSubnodes("alternatives"),
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sequence: replaceInSubnodes("elements"),
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labeled: replaceInExpression,
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text: replaceInExpression,
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simple_and: replaceInExpression,
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simple_not: replaceInExpression,
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semantic_and: nop,
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semantic_not: nop,
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optional: replaceInExpression,
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zero_or_more: replaceInExpression,
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one_or_more: replaceInExpression,
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action: replaceInExpression,
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rule_ref:
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function(node, from, to) {
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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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literal: nop,
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"class": nop,
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any: nop
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});
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replace(ast, from, to);
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}
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var indices = [];
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utils.each(ast.rules, function(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 (rule.name === ast.startRule) {
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ast.startRule = rule.expression.name;
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}
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indices.push(i);
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}
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});
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indices.reverse();
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utils.each(indices, function(index) {
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ast.rules.splice(index, 1);
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});
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};
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