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/*!
* Chai - addChainingMethod utility
* Copyright(c) 2012-2014 Jake Luer <jake@alogicalparadox.com>
* MIT Licensed
*/
/*!
* Module dependencies
*/
var addLengthGuard = require('./addLengthGuard');
var chai = require('../../chai');
var flag = require('./flag');
var proxify = require('./proxify');
var transferFlags = require('./transferFlags');
/*!
* Module variables
*/
// Check whether `Object.setPrototypeOf` is supported
var canSetPrototype = typeof Object.setPrototypeOf === 'function';
// Without `Object.setPrototypeOf` support, this module will need to add properties to a function.
// However, some of functions' own props are not configurable and should be skipped.
var testFn = function() {};
var excludeNames = Object.getOwnPropertyNames(testFn).filter(function(name) {
var propDesc = Object.getOwnPropertyDescriptor(testFn, name);
// Note: PhantomJS 1.x includes `callee` as one of `testFn`'s own properties,
// but then returns `undefined` as the property descriptor for `callee`. As a
// workaround, we perform an otherwise unnecessary type-check for `propDesc`,
// and then filter it out if it's not an object as it should be.
if (typeof propDesc !== 'object')
return true;
return !propDesc.configurable;
});
// Cache `Function` properties
var call = Function.prototype.call,
apply = Function.prototype.apply;
/**
* ### .addChainableMethod(ctx, name, method, chainingBehavior)
*
* Adds a method to an object, such that the method can also be chained.
*
* utils.addChainableMethod(chai.Assertion.prototype, 'foo', function (str) {
* var obj = utils.flag(this, 'object');
* new chai.Assertion(obj).to.be.equal(str);
* });
*
* Can also be accessed directly from `chai.Assertion`.
*
* chai.Assertion.addChainableMethod('foo', fn, chainingBehavior);
*
* The result can then be used as both a method assertion, executing both `method` and
* `chainingBehavior`, or as a language chain, which only executes `chainingBehavior`.
*
* expect(fooStr).to.be.foo('bar');
* expect(fooStr).to.be.foo.equal('foo');
*
* @param {Object} ctx object to which the method is added
* @param {String} name of method to add
* @param {Function} method function to be used for `name`, when called
* @param {Function} chainingBehavior function to be called every time the property is accessed
* @namespace Utils
* @name addChainableMethod
* @api public
*/
module.exports = function addChainableMethod(ctx, name, method, chainingBehavior) {
if (typeof chainingBehavior !== 'function') {
chainingBehavior = function () { };
}
var chainableBehavior = {
method: method
, chainingBehavior: chainingBehavior
};
// save the methods so we can overwrite them later, if we need to.
if (!ctx.__methods) {
ctx.__methods = {};
}
ctx.__methods[name] = chainableBehavior;
Object.defineProperty(ctx, name,
{ get: function chainableMethodGetter() {
chainableBehavior.chainingBehavior.call(this);
var chainableMethodWrapper = function () {
// Setting the `ssfi` flag to `chainableMethodWrapper` 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 this assertion is being
// invoked from inside of another assertion. In this case, the `ssfi`
// flag has already been set by the outer assertion.
//
// Note that overwriting a chainable method merely replaces the saved
// methods in `ctx.__methods` instead of completely replacing the
// overwritten assertion. Therefore, an overwriting assertion won't
// set the `ssfi` or `lockSsfi` flags.
if (!flag(this, 'lockSsfi')) {
flag(this, 'ssfi', chainableMethodWrapper);
}
var result = chainableBehavior.method.apply(this, arguments);
if (result !== undefined) {
return result;
}
var newAssertion = new chai.Assertion();
transferFlags(this, newAssertion);
return newAssertion;
};
addLengthGuard(chainableMethodWrapper, name, true);
// Use `Object.setPrototypeOf` if available
if (canSetPrototype) {
// Inherit all properties from the object by replacing the `Function` prototype
var prototype = Object.create(this);
// Restore the `call` and `apply` methods from `Function`
prototype.call = call;
prototype.apply = apply;
Object.setPrototypeOf(chainableMethodWrapper, prototype);
}
// Otherwise, redefine all properties (slow!)
else {
var asserterNames = Object.getOwnPropertyNames(ctx);
asserterNames.forEach(function (asserterName) {
if (excludeNames.indexOf(asserterName) !== -1) {
return;
}
var pd = Object.getOwnPropertyDescriptor(ctx, asserterName);
Object.defineProperty(chainableMethodWrapper, asserterName, pd);
});
}
transferFlags(this, chainableMethodWrapper);
return proxify(chainableMethodWrapper);
}
, configurable: true
});
};
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