fix(elements): support output()-shaped outputs (#57535)

Previously Elements was assuming that every output was an RxJS `Subject` and
supports `.pipe()`. This is not true for `output()`-based outputs which
have `.subscribe()` but not `.pipe()`. This commit fixes such outputs by
using a `new Observable` instead of `map` to forward outputs.

PR Close #57535

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

@@ -18,9 +18,10 @@ import {
   ɵChangeDetectionScheduler as ChangeDetectionScheduler,
   ɵNotificationSource as NotificationSource,
   ɵViewRef as ViewRef,
+  OutputRef,
 } from '@angular/core';
 import {merge, Observable, ReplaySubject} from 'rxjs';
-import {map, switchMap} from 'rxjs/operators';
+import {switchMap} from 'rxjs/operators';
 
 import {
   NgElementStrategy,
@@ -219,8 +220,11 @@ export class ComponentNgElementStrategy implements NgElementStrategy {
   protected initializeOutputs(componentRef: ComponentRef<any>): void {
     const eventEmitters: Observable<NgElementStrategyEvent>[] = this.componentFactory.outputs.map(
       ({propName, templateName}) => {
-        const emitter: EventEmitter<any> = componentRef.instance[propName];
-        return emitter.pipe(map((value) => ({name: templateName, value})));
+        const emitter: EventEmitter<any> | OutputRef<any> = componentRef.instance[propName];
+        return new Observable((observer) => {
+          const sub = emitter.subscribe((value) => observer.next({name: templateName, value}));
+          return () => sub.unsubscribe();
+        });
       },
     );
 

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

@@ -16,6 +16,7 @@ import {
   Input,
   NgZone,
   Output,
+  OutputEmitterRef,
   SimpleChange,
   SimpleChanges,
   createComponent,
@@ -113,6 +114,18 @@ describe('ComponentFactoryNgElementStrategy', () => {
       ]);
     });
 
+    it('should listen to output() emitters', () => {
+      const events: NgElementStrategyEvent[] = [];
+      strategy.events.subscribe((e) => events.push(e));
+
+      componentRef.instance.output3.emit('output-a');
+      componentRef.instance.output3.emit('output-b');
+      expect(events).toEqual([
+        {name: 'templateOutput3', value: 'output-a'},
+        {name: 'templateOutput3', value: 'output-b'},
+      ]);
+    });
+
     it('should initialize the component with initial values', () => {
       expect(strategy.getInputValue('fooFoo')).toBe('fooFoo-1');
       expect(componentRef.instance.fooFoo).toBe('fooFoo-1');
@@ -369,6 +382,7 @@ export class CdTrackerDir {
 export class TestComponent {
   @Output('templateOutput1') output1 = new Subject();
   @Output('templateOutput2') output2 = new Subject();
+  @Output('templateOutput3') output3 = new OutputEmitterRef();
 
   @Input() fooFoo: unknown;
   @Input({alias: 'my-bar-bar'}) barBar: unknown;