perf(Controller): reduce object allocation needed for isConnected prop (

microsoft#5160)

* perf(Controller): reduce object allocation needed for isConnected prop

* test(Controller): add notifier resolution test

* Change files

Co-authored-by: EisenbergEffect <roeisenb@microsoft.com>

change/@microsoft-fast-element-569ad956-2e34-469a-95aa-c78dc05d45ff.json

@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "perf(Controller): reduce object allocation needed for isConnected prop",
+  "packageName": "@microsoft/fast-element",
+  "email": "roeisenb@microsoft.com",
+  "dependentChangeType": "patch"
+}

packages/web-components/fast-element/src/components/controller.spec.ts

@@ -308,6 +308,12 @@ describe("The Controller", () => {
         }
     });
 
+    it("should use itself as the notifier", () => {
+        const { controller } = createController();
+        const notifier = Observable.getNotifier(controller);
+        expect(notifier).to.equal(controller);
+    });
+
     it("should have an observable isConnected property", () => {
         const { element, controller } = createController();
         let attached = controller.isConnected;

packages/web-components/fast-element/src/components/controller.ts

@@ -31,6 +31,16 @@ export class Controller extends PropertyChangeNotifier {
     private _styles: ElementStyles | null = null;
     private _isConnected: boolean = false;
 
+    /**
+     * This allows Observable.getNotifier(...) to return the Controller
+     * when the notifier for the Controller itself is being requested. The
+     * result is that the Observable system does not need to create a separate
+     * instance of Notifier for observables on the Controller. The component and
+     * the controller will now share the same notifier, removing one-object construct
+     * per web component instance.
+     */
+    private readonly $fastController = this;
+
     /**
      * The element being controlled by this controller.
      */