overwriteChainableMethod.js

/*!
 * Chai - overwriteChainableMethod utility
 * Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
 * MIT Licensed
 */

/**
 * ### overwriteChainableMethod (ctx, name, method, chainingBehavior)
 *
 * Overwites an already existing chainable method
 * and provides access to the previous function or
 * property.  Must return functions to be used for
 * name.
 *
 *     utils.overwriteChainableMethod(chai.Assertion.prototype, 'length',
 *       function (_super) {
 *       }
 *     , function (_super) {
 *       }
 *     );
 *
 * Can also be accessed directly from `chai.Assertion`.
 *
 *     chai.Assertion.overwriteChainableMethod('foo', fn, fn);
 *
 * Then can be used as any other assertion.
 *
 *     expect(myFoo).to.have.length(3);
 *     expect(myFoo).to.have.length.above(3);
 *
 * @param {Object} ctx object whose method / property is to be overwritten
 * @param {String} name of method / property to overwrite
 * @param {Function} method function that returns a function to be used for name
 * @param {Function} chainingBehavior function that returns a function to be used for property
 * @namespace Utils
 * @name overwriteChainableMethod
 * @api public
 */

module.exports = function (ctx, name, method, chainingBehavior) {
  var chainableBehavior = ctx.__methods[name];

  var _chainingBehavior = chainableBehavior.chainingBehavior;
  chainableBehavior.chainingBehavior = function () {
    var result = chainingBehavior(_chainingBehavior).call(this);
    return result === undefined ? this : result;
  };

  var _method = chainableBehavior.method;
  chainableBehavior.method = function () {
    var result = method(_method).apply(this, arguments);
    return result === undefined ? this : result;
  };
};