pegjs/lib/compiler.js

var utils = require("./utils");

module.exports = {
  /*
   * Compiler passes.
   *
   * Each pass is a function that is passed the AST. It can perform checks on it
   * or modify it as needed. If the pass encounters a semantic error, it throws
   * |PEG.GrammarError|.
   */
  passes: {
    check: {
      reportMissingRules:  require("./compiler/passes/report-missing-rules"),
      reportLeftRecursion: require("./compiler/passes/report-left-recursion")
    },
    transform: {
      removeProxyRules:    require("./compiler/passes/remove-proxy-rules")
    },
    generate: {
      generateBytecode:    require("./compiler/passes/generate-bytecode"),
      generateJavascript:  require("./compiler/passes/generate-javascript")
    }
  },

  /*
   * Generates a parser from a specified grammar AST. Throws |PEG.GrammarError|
   * if the AST contains a semantic error. Note that not all errors are detected
   * during the generation and some may protrude to the generated parser and
   * cause its malfunction.
   */
  compile: function(ast, passes) {
    var options = arguments.length > 2 ? utils.clone(arguments[2]) : {},
        stage;

    /*
     * Extracted into a function just to silence JSHint complaining about
     * creating functions in a loop.
     */
    function runPass(pass) {
      pass(ast, options);
    }

    utils.defaults(options, {
      allowedStartRules:  [ast.rules[0].name],
      cache:              false,
      optimize:           "speed",
      output:             "parser"
    });

    for (stage in passes) {
      utils.each(passes[stage], runPass);
    }

    switch (options.output) {
      case "parser": return eval(ast.code);
      case "source": return ast.code;
    }
  }
};