93 lines
3.2 KiB
Plaintext
93 lines
3.2 KiB
Plaintext
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/*!
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* Chai - overwriteProperty utility
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* Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
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* MIT Licensed
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*/
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var chai = require('../../chai');
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var flag = require('./flag');
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var isProxyEnabled = require('./isProxyEnabled');
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var transferFlags = require('./transferFlags');
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/**
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* ### .overwriteProperty(ctx, name, fn)
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*
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* Overwrites an already existing property getter and provides
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* access to previous value. Must return function to use as getter.
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*
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* utils.overwriteProperty(chai.Assertion.prototype, 'ok', function (_super) {
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* return function () {
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* var obj = utils.flag(this, 'object');
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* if (obj instanceof Foo) {
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* new chai.Assertion(obj.name).to.equal('bar');
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* } else {
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* _super.call(this);
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* }
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* }
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* });
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*
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*
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* Can also be accessed directly from `chai.Assertion`.
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*
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* chai.Assertion.overwriteProperty('foo', fn);
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*
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* Then can be used as any other assertion.
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*
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* expect(myFoo).to.be.ok;
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*
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* @param {Object} ctx object whose property is to be overwritten
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* @param {String} name of property to overwrite
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* @param {Function} getter function that returns a getter function to be used for name
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* @namespace Utils
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* @name overwriteProperty
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* @api public
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*/
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module.exports = function overwriteProperty(ctx, name, getter) {
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var _get = Object.getOwnPropertyDescriptor(ctx, name)
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, _super = function () {};
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if (_get && 'function' === typeof _get.get)
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_super = _get.get
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Object.defineProperty(ctx, name,
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{ get: function overwritingPropertyGetter() {
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// Setting the `ssfi` flag to `overwritingPropertyGetter` causes this
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// function to be the starting point for removing implementation frames
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// from the stack trace of a failed assertion.
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//
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// However, we only want to use this function as the starting point if
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// the `lockSsfi` flag isn't set and proxy protection is disabled.
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//
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// If the `lockSsfi` flag is set, then either this assertion has been
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// overwritten by another assertion, or this assertion is being invoked
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// from inside of another assertion. In the first case, the `ssfi` flag
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// has already been set by the overwriting assertion. In the second
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// case, the `ssfi` flag has already been set by the outer assertion.
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//
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// If proxy protection is enabled, then the `ssfi` flag has already been
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// set by the proxy getter.
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if (!isProxyEnabled() && !flag(this, 'lockSsfi')) {
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flag(this, 'ssfi', overwritingPropertyGetter);
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}
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// Setting the `lockSsfi` flag to `true` prevents the overwritten
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// assertion from changing the `ssfi` flag. By this point, the `ssfi`
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// flag is already set to the correct starting point for this assertion.
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var origLockSsfi = flag(this, 'lockSsfi');
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flag(this, 'lockSsfi', true);
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var result = getter(_super).call(this);
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flag(this, 'lockSsfi', origLockSsfi);
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if (result !== undefined) {
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return result;
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}
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var newAssertion = new chai.Assertion();
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transferFlags(this, newAssertion);
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return newAssertion;
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}
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, configurable: true
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});
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};
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