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/*!
* Chai - overwriteMethod utility
* Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
* MIT Licensed
*/
var addLengthGuard = require('./addLengthGuard');
var chai = require('../../chai');
var flag = require('./flag');
var proxify = require('./proxify');
var transferFlags = require('./transferFlags');
/**
* ### .overwriteMethod(ctx, name, fn)
*
* Overwrites an already existing method and provides
* access to previous function. Must return function
* to be used for name.
*
* utils.overwriteMethod(chai.Assertion.prototype, 'equal', function (_super) {
* return function (str) {
* var obj = utils.flag(this, 'object');
* if (obj instanceof Foo) {
* new chai.Assertion(obj.value).to.equal(str);
* } else {
* _super.apply(this, arguments);
* }
* }
* });
*
* Can also be accessed directly from `chai.Assertion`.
*
* chai.Assertion.overwriteMethod('foo', fn);
*
* Then can be used as any other assertion.
*
* expect(myFoo).to.equal('bar');
*
* @param {Object} ctx object whose method is to be overwritten
* @param {String} name of method to overwrite
* @param {Function} method function that returns a function to be used for name
* @namespace Utils
* @name overwriteMethod
* @api public
*/
module.exports = function overwriteMethod(ctx, name, method) {
var _method = ctx[name]
, _super = function () {
throw new Error(name + ' is not a function');
};
if (_method && 'function' === typeof _method)
_super = _method;
var overwritingMethodWrapper = function () {
// Setting the `ssfi` flag to `overwritingMethodWrapper` causes this
// function to be the starting point for removing implementation frames from
// the stack trace of a failed assertion.
//
// However, we only want to use this function as the starting point if the
// `lockSsfi` flag isn't set.
//
// If the `lockSsfi` flag is set, then either this assertion has been
// overwritten by another assertion, or this assertion is being invoked from
// inside of another assertion. In the first case, the `ssfi` flag has
// already been set by the overwriting assertion. In the second case, the
// `ssfi` flag has already been set by the outer assertion.
if (!flag(this, 'lockSsfi')) {
flag(this, 'ssfi', overwritingMethodWrapper);
}
// Setting the `lockSsfi` flag to `true` prevents the overwritten assertion
// from changing the `ssfi` flag. By this point, the `ssfi` flag is already
// set to the correct starting point for this assertion.
var origLockSsfi = flag(this, 'lockSsfi');
flag(this, 'lockSsfi', true);
var result = method(_super).apply(this, arguments);
flag(this, 'lockSsfi', origLockSsfi);
if (result !== undefined) {
return result;
}
var newAssertion = new chai.Assertion();
transferFlags(this, newAssertion);
return newAssertion;
}
addLengthGuard(overwritingMethodWrapper, name, false);
ctx[name] = proxify(overwritingMethodWrapper, name);
};
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