Bug 1478124: Part 1 - Update component mocks to replace and restore components sanely. r=froydnj

For static components, I don't intend to allow removing or replacing CID
entries, only contract ID entries. And I would generally prefer, when
restoring overrides of those classes, to not create a new dynamic factory
entry for the contract ID.

We already have the ability to mock components without either of those issues,
but registering a new CID entry for the mock (without unregistering the
original), and then restoring the original by calling `registerFactory` with a
null factory object.

This patch updates our existing mocks to behave that way, and paves the way
for the rest of the patches.

Differential Revision: https://phabricator.services.mozilla.com/D15031

--HG--
extra : rebase_source : 449f37ae8a3cc970e5f864d10e43e88d9e7e4bf6
extra : source : bedaa9c437ad30ea88bdc0e8fc83f4a2e980812e

dom/presentation/tests/mochitest/PresentationSessionChromeScript.js

@@ -25,9 +25,6 @@ function registerMockedFactory(contractId, mockedClassId, mockedFactory) {
       originalClassId = "";
       originalFactory = null;
     }
-    if (originalFactory) {
-      registrar.unregisterFactory(originalClassId, originalFactory);
-    }
     registrar.registerFactory(mockedClassId, "", contractId, mockedFactory);
   }
 
@@ -42,7 +39,9 @@ function registerOriginalFactory(contractId, mockedClassId, mockedFactory, origi
   if (originalFactory) {
     var registrar = Cm.QueryInterface(Ci.nsIComponentRegistrar);
     registrar.unregisterFactory(mockedClassId, mockedFactory);
-    registrar.registerFactory(originalClassId, "", contractId, originalFactory);
+    // Passing null for the factory remaps the original CID to the
+    // contract ID.
+    registrar.registerFactory(originalClassId, "", contractId, null);
   }
 }
 

testing/modules/MockRegistrar.jsm

@@ -11,8 +11,13 @@ var EXPORTED_SYMBOLS = [
 const Cm = Components.manager;
 
 const {Log} = ChromeUtils.import("resource://gre/modules/Log.jsm");
+const {XPCOMUtils} = ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
 var logger = Log.repository.getLogger("MockRegistrar");
 
+XPCOMUtils.defineLazyServiceGetter(this, "UUIDGen",
+                                   "@mozilla.org/uuid-generator;1",
+                                   "nsIUUIDGenerator");
+
 var MockRegistrar = Object.freeze({
   _registeredComponents: new Map(),
   _originalCIDs: new Map(),
@@ -44,6 +49,8 @@ var MockRegistrar = Object.freeze({
 
     let originalFactory = Cm.getClassObject(originalCID, Ci.nsIFactory);
 
+    let cid = UUIDGen.generateUUID();
+
     let factory = {
       createInstance(outer, iid) {
         if (outer) {
@@ -73,19 +80,18 @@ var MockRegistrar = Object.freeze({
       QueryInterface: ChromeUtils.generateQI([Ci.nsIFactory]),
     };
 
-    this.registrar.unregisterFactory(originalCID, originalFactory);
-    this.registrar.registerFactory(originalCID,
+    this.registrar.registerFactory(cid,
                                    "A Mock for " + contractID,
                                    contractID,
                                    factory);
 
-    this._registeredComponents.set(originalCID, {
+    this._registeredComponents.set(cid, {
       contractID,
       factory,
-      originalFactory,
+      originalCID,
     });
 
-    return originalCID;
+    return cid;
   },
 
   /**
@@ -100,11 +106,12 @@ var MockRegistrar = Object.freeze({
     }
 
     this.registrar.unregisterFactory(cid, component.factory);
-    if (component.originalFactory) {
-      this.registrar.registerFactory(cid,
-                                     "",
+    if (component.originalCID) {
+      // Passing `null` for the factory re-maps the contract ID to the
+      // entry for its original CID.
+      this.registrar.registerFactory(component.originalCID, "",
                                      component.contractID,
-                                     component.originalFactory);
+                                     null);
     }
 
     this._registeredComponents.delete(cid);

testing/xpcshell/head.js

@@ -248,18 +248,17 @@ var _fakeIdleService = {
       Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
   },
   contractID: "@mozilla.org/widget/idleservice;1",
-  get CID() {
-    return this.registrar.contractIDToCID(this.contractID);
-  },
+  CID: Components.ID("{9163a4ae-70c2-446c-9ac1-bbe4ab93004e}"),
 
   activate: function FIS_activate() {
-    if (!this.originalFactory) {
-      // Save original factory.
-      this.originalFactory =
-        Components.manager.getClassObject(Cc[this.contractID],
-                                          Ci.nsIFactory);
-      // Unregister original factory.
-      this.registrar.unregisterFactory(this.CID, this.originalFactory);
+    if (!this.originalCID) {
+      // This is useless, except to the extent that it has the
+      // side-effect of initializing the widget module, which some
+      // callers unfortunately accidentally rely on.
+      void Components.manager.getClassObject(Cc[this.contractID],
+                                             Ci.nsIFactory);
+
+      this.originalCID = this.registrar.contractIDToCID(this.contractID);
       // Replace with the mock.
       this.registrar.registerFactory(this.CID, "Fake Idle Service",
                                      this.contractID, this.factory
@@ -268,13 +267,13 @@ var _fakeIdleService = {
   },
 
   deactivate: function FIS_deactivate() {
-    if (this.originalFactory) {
+    if (this.originalCID) {
       // Unregister the mock.
       this.registrar.unregisterFactory(this.CID, this.factory);
       // Restore original factory.
-      this.registrar.registerFactory(this.CID, "Idle Service",
-                                     this.contractID, this.originalFactory);
-      delete this.originalFactory;
+      this.registrar.registerFactory(this.originalCID, "Idle Service",
+                                     this.contractID, null);
+      delete this.originalCID;
     }
   },