95ce20ed92
Beside the recursion detector, the visitor will also be used by infinite loop detector. Note the newly created |asts.matchesEmpty| function re-creates the visitor each time it is called, which makes it slower than necessary. This could have been worked around in various ways but I chose to defer that optimization because real-world performance impact is small.
62 lines
1.4 KiB
JavaScript
62 lines
1.4 KiB
JavaScript
var arrays = require("../utils/arrays"),
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visitor = require("./visitor");
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/* AST utilities. */
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var asts = {
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findRule: function(ast, name) {
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return arrays.find(ast.rules, function(r) { return r.name === name; });
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},
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indexOfRule: function(ast, name) {
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return arrays.indexOf(ast.rules, function(r) { return r.name === name; });
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},
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matchesEmpty: function(ast, node) {
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function matchesTrue() { return true; }
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function matchesFalse() { return false; }
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function matchesExpression(node) {
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return matches(node.expression);
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}
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var matches = visitor.build({
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rule: matchesExpression,
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choice: function(node) {
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return arrays.some(node.alternatives, matches);
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},
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action: matchesExpression,
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sequence: function(node) {
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return arrays.every(node.elements, matches);
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},
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labeled: matchesExpression,
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text: matchesExpression,
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simple_and: matchesTrue,
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simple_not: matchesTrue,
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optional: matchesTrue,
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zero_or_more: matchesTrue,
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one_or_more: matchesExpression,
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semantic_and: matchesTrue,
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semantic_not: matchesTrue,
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rule_ref: function(node) {
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return matches(asts.findRule(ast, node.name));
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},
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literal: function(node) {
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return node.value === "";
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},
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"class": matchesFalse,
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any: matchesFalse
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});
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return matches(node);
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}
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};
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module.exports = asts;
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