Transparent function and generator proxy

util.js

var toString$ = Object.prototype.toString;

// Ported from angular.js
var COMMENTS_PATTERN = /((\/\/.*$)|(\/\*[\s\S]*?\*\/))/mg,
    ARGS_PATTERN = /^function\s*(\*)?\s*[^\(]*\(\s*([^\)]*)\)/m,
    ARG_PATTERN = /^\s*(_?)(\S+?)\1\s*$/;

module.exports = {
  isGenerator: function isGenerator(obj) {
    return toString$.call(obj).slice(8, -1) === 'Generator';
  },
  extractArgs: function(fn){
    var source, ref$, _, genMarker, fnArgs, argArray;
    var source = fn.toString().replace(COMMENTS_PATTERN, '');
    var fnArgs = (source.match(ARGS_PATTERN))[2];
    return fnArgs.split(',').map(function(arg) {
      return arg.replace(ARG_PATTERN, '$2');
    }).filter(function(arg) {
      return !!arg;
    });
  }
};

wrap-generator.js

'use strict';

var Q           = require('q'),
    isGenerator = require('./util').isGenerator,
    extractArgs = require('./util').extractArgs;

// ported from Q
var wrapGenerator = module.exports = function wrapGenerator(makeGenerator) {
  var inner = function() {
    var callback, errback;

    function continuer(verb, arg) {
      try {
        var result = generator[verb](arg);
        return result.done ?
          result.value : Q.when(result.value, callback, errback);
      } catch (exception) {
        return Q.reject(exception);
      }
    }

    var generator = makeGenerator.apply(this, arguments);
    if (isGenerator(generator)) {
      callback = continuer.bind(this, 'next');
      errback = continuer.bind(this, 'throw');
      return callback();
    } else {
      return Q.when(generator);
    }
  };

  var originalArgs = extractArgs(makeGenerator);
  var fnProxy = new Function('inner', [
    'return function (' + originalArgs.join(', ') + ') {',
    '  return inner(' + originalArgs.join(', ') + ');',
    '};'
  ].join(''));
  return fnProxy(inner);
}

if (module.parent == null) {
  var assert = require('assert');

  var fn = function (a, b) { return a + b; };
  var args = extractArgs(fn);
  assert.equal(args.length, 2);
  assert.equal(args[0], 'a');
  assert.equal(args[1], 'b');
  assert.equal(fn(2, 3), 5);

  var wrapped = wrapGenerator(fn);
  assert.equal(wrapped.length, 2);
  var args = extractArgs(wrapped);
  assert.equal(args.length, 2);
  assert.equal(args[0], 'a');
  assert.equal(args[1], 'b');
  wrapped(2, 3).done(function(result) {
    assert.equal(result, 5);
    console.log('ok');
  });
}