Revert "fix(elements): fire custom element output events during component initialization (#36161)" (#37524)

This reverts commit e9bff5fe9f40d87b2164fc4f667f2cdd0afd4634. Failures
were detected in Google tests due to this commit

PR Close #37524

packages/elements/src/component-factory-strategy.ts

@@ -7,8 +7,8 @@
  */
 
 import {ApplicationRef, ComponentFactory, ComponentFactoryResolver, ComponentRef, EventEmitter, Injector, OnChanges, SimpleChange, SimpleChanges, Type} from '@angular/core';
-import {merge, Observable, ReplaySubject} from 'rxjs';
+import {merge, Observable} from 'rxjs';
-import {map, switchMap} from 'rxjs/operators';
+import {map} from 'rxjs/operators';
 
 import {NgElementStrategy, NgElementStrategyEvent, NgElementStrategyFactory} from './element-strategy';
 import {extractProjectableNodes} from './extract-projectable-nodes';
@@ -43,11 +43,9 @@ export class ComponentNgElementStrategyFactory implements NgElementStrategyFacto
  * @publicApi
  */
 export class ComponentNgElementStrategy implements NgElementStrategy {
-  // Subject of `NgElementStrategyEvent` observables corresponding to the component's outputs.
-  private eventEmitters = new ReplaySubject<Observable<NgElementStrategyEvent>[]>(1);
-
   /** Merged stream of the component's output events. */
-  readonly events = this.eventEmitters.pipe(switchMap(emitters => merge(...emitters)));
+  // TODO(issue/24571): remove '!'.
+  events!: Observable<NgElementStrategyEvent>;
 
   /** Reference to the component that was created on connect. */
   private componentRef: ComponentRef<any>|null = null;
@@ -189,13 +187,12 @@ export class ComponentNgElementStrategy implements NgElementStrategy {
 
   /** Sets up listeners for the component's outputs so that the events stream emits the events. */
   protected initializeOutputs(componentRef: ComponentRef<any>): void {
-    const eventEmitters: Observable<NgElementStrategyEvent>[] =
+    const eventEmitters = this.componentFactory.outputs.map(({propName, templateName}) => {
-        this.componentFactory.outputs.map(({propName, templateName}) => {
       const emitter: EventEmitter<any> = componentRef.instance[propName];
       return emitter.pipe(map(value => ({name: templateName, value})));
     });
 
-    this.eventEmitters.next(eventEmitters);
+    this.events = merge(...eventEmitters);
   }
 
   /** Calls ngOnChanges with all the inputs that have changed since the last call. */

packages/elements/src/create-custom-element.ts

@@ -187,13 +187,13 @@ export function createCustomElement<P>(
     }
 
     connectedCallback(): void {
+      this.ngElementStrategy.connect(this);
+
       // Listen for events from the strategy and dispatch them as custom events
       this.ngElementEventsSubscription = this.ngElementStrategy.events.subscribe(e => {
         const customEvent = createCustomEvent(this.ownerDocument!, e.name, e.value);
         this.dispatchEvent(customEvent);
       });
-
-      this.ngElementStrategy.connect(this);
     }
 
     disconnectedCallback(): void {

packages/elements/test/component-factory-strategy_spec.ts

@@ -41,33 +41,6 @@ describe('ComponentFactoryNgElementStrategy', () => {
     expect(strategyFactory.create(injector)).toBeTruthy();
   });
 
-  describe('before connected', () => {
-    it('should allow subscribing to output events', () => {
-      const events: NgElementStrategyEvent[] = [];
-      strategy.events.subscribe(e => events.push(e));
-
-      // No events before connecting (since `componentRef` is not even on the strategy yet).
-      componentRef.instance.output1.next('output-1a');
-      componentRef.instance.output1.next('output-1b');
-      componentRef.instance.output2.next('output-2a');
-      expect(events).toEqual([]);
-
-      // No events upon connecting (since events are not cached/played back).
-      strategy.connect(document.createElement('div'));
-      expect(events).toEqual([]);
-
-      // Events emitted once connected.
-      componentRef.instance.output1.next('output-1c');
-      componentRef.instance.output1.next('output-1d');
-      componentRef.instance.output2.next('output-2b');
-      expect(events).toEqual([
-        {name: 'templateOutput1', value: 'output-1c'},
-        {name: 'templateOutput1', value: 'output-1d'},
-        {name: 'templateOutput2', value: 'output-2b'},
-      ]);
-    });
-  });
-
   describe('after connected', () => {
     beforeEach(() => {
       // Set up an initial value to make sure it is passed to the component

packages/elements/test/create-custom-element_spec.ts

@@ -117,16 +117,6 @@ if (browserDetection.supportsCustomElements) {
       expect(eventValue).toEqual(null);
     });
 
-    it('should listen to output events during initialization', () => {
-      const events: string[] = [];
-
-      const element = new NgElementCtor(injector);
-      element.addEventListener('strategy-event', evt => events.push((evt as CustomEvent).detail));
-      element.connectedCallback();
-
-      expect(events).toEqual(['connect']);
-    });
-
     it('should properly set getters/setters on the element', () => {
       const element = new NgElementCtor(injector);
       element.fooFoo = 'foo-foo-value';
@@ -265,7 +255,6 @@ if (browserDetection.supportsCustomElements) {
       events = new Subject<NgElementStrategyEvent>();
 
       connect(element: HTMLElement): void {
-        this.events.next({name: 'strategy-event', value: 'connect'});
         this.connectedElement = element;
       }