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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
/**
* Allows registering a mock XPCOM component, that temporarily replaces the
* original one when an object implementing a given ContractID is requested
* using createInstance.
*
* @param aContractID
* The ContractID of the component to replace, for example
* "@mozilla.org/filepicker;1".
*
* @param aReplacementCtor
* The constructor function for the JavaScript object that will be
* created every time createInstance is called. This object must
* implement QueryInterface and provide the XPCOM interfaces required by
* the specified ContractID (for example
* Components.interfaces.nsIFilePicker).
*/
function MockObjectRegisterer(aContractID, aReplacementCtor) {
this._contractID = aContractID;
this._replacementCtor = aReplacementCtor;
}
MockObjectRegisterer.prototype = {
/**
* Replaces the current factory with one that returns a new mock object.
*
* After register() has been called, it is mandatory to call unregister() to
* restore the original component. Usually, you should use a try-catch block
* to ensure that unregister() is called.
*/
register: function MOR_register() {
if (this._originalCID) {
throw new Error("Invalid object state when calling register()");
}
// Define a factory that creates a new object using the given constructor.
var isChrome = location.protocol == "chrome:";
var providedConstructor = this._replacementCtor;
this._mockFactory = {
createInstance: function MF_createInstance(aIid) {
var inst = new providedConstructor().QueryInterface(aIid);
if (!isChrome) {
inst = SpecialPowers.wrapCallbackObject(inst);
}
return inst;
},
};
if (!isChrome) {
this._mockFactory = SpecialPowers.wrapCallbackObject(this._mockFactory);
}
var retVal = SpecialPowers.swapFactoryRegistration(
null,
this._contractID,
this._mockFactory
);
if ("error" in retVal) {
throw new Error("ERROR: " + retVal.error);
} else {
this._originalCID = retVal.originalCID;
}
},
/**
* Restores the original factory.
*/
unregister: function MOR_unregister() {
if (!this._originalCID) {
throw new Error("Invalid object state when calling unregister()");
}
// Free references to the mock factory.
SpecialPowers.swapFactoryRegistration(this._originalCID, this._contractID);
// Allow registering a mock factory again later.
this._originalCID = null;
this._mockFactory = null;
},
// --- Private methods and properties ---
/**
* The factory of the component being replaced.
*/
_originalCID: null,
/**
* The nsIFactory that was automatically generated by this object.
*/
_mockFactory: null,
};