pegjs/lib/compiler/passes/report-infinite-repetition.js

"use strict";

var GrammarError = require("../../grammar-error"),
    asts         = require("../asts"),
    visitor      = require("../visitor");

/*
 * Reports expressions that don't consume any input inside |*| or |+| in the
 * grammar, which prevents infinite loops in the generated parser.
 */
function reportInfiniteRepetition(ast) {
  var check = visitor.build({
    zero_or_more: function(node) {
      if (!asts.alwaysConsumesOnSuccess(ast, node.expression)) {
        throw new GrammarError(
          "Possible infinite loop when parsing (repetition used with an expression that may not consume any input).",
          node.location
        );
      }
    },

    one_or_more: function(node) {
      if (!asts.alwaysConsumesOnSuccess(ast, node.expression)) {
        throw new GrammarError(
          "Possible infinite loop when parsing (repetition used with an expression that may not consume any input).",
          node.location
        );
      }
    }
  });

  check(ast);
}

module.exports = reportInfiniteRepetition;