fix(component): fixes recursive rendering (#3255)

Closes #3246

Author: e-davidson

modules/component/spec/let/let.directive.spec.ts

@@ -1,6 +1,7 @@
 import {
   ChangeDetectorRef,
   Component,
+  Directive,
   TemplateRef,
   ViewContainerRef,
 } from '@angular/core';
@@ -13,6 +14,7 @@ import {
   waitForAsync,
 } from '@angular/core/testing';
 import {
+  BehaviorSubject,
   EMPTY,
   interval,
   NEVER,
@@ -60,6 +62,29 @@ class LetDirectiveTestCompleteComponent {
   value$: Observable<number> = of(42);
 }
 
+@Directive({
+  selector: '[recursiveDirective]',
+})
+export class RecursiveDirective {
+  constructor(private subject: BehaviorSubject<number>) {
+    this.subject.next(1);
+  }
+}
+
+@Component({
+  template: `
+    <ng-container recursiveDirective *ngrxLet="subject as value">{{
+      value
+    }}</ng-container>
+  `,
+})
+class LetDirectiveTestRecursionComponent {
+  constructor(public subject: BehaviorSubject<number>) {}
+  get value$() {
+    return this.subject;
+  }
+}
+
 let fixtureLetDirectiveTestComponent: ComponentFixture<LetDirectiveTestComponent>;
 let letDirectiveTestComponent: {
   value$: ObservableInput<any> | undefined | null;
@@ -117,6 +142,29 @@ const setupLetDirectiveTestComponentComplete = (): void => {
   componentNativeElement = fixtureLetDirectiveTestComponent.nativeElement;
 };
 
+const setupLetDirectiveTestRecursionComponent = (): void => {
+  const subject = new BehaviorSubject(0);
+  TestBed.configureTestingModule({
+    declarations: [
+      LetDirectiveTestRecursionComponent,
+      RecursiveDirective,
+      LetDirective,
+    ],
+    providers: [
+      { provide: ChangeDetectorRef, useClass: MockChangeDetectorRef },
+      TemplateRef,
+      ViewContainerRef,
+      { provide: BehaviorSubject, useValue: subject },
+    ],
+  });
+  fixtureLetDirectiveTestComponent = TestBed.createComponent(
+    LetDirectiveTestRecursionComponent
+  );
+  letDirectiveTestComponent =
+    fixtureLetDirectiveTestComponent.componentInstance;
+  componentNativeElement = fixtureLetDirectiveTestComponent.nativeElement;
+};
+
 describe('LetDirective', () => {
   describe('when nexting values', () => {
     beforeEach(waitForAsync(setupLetDirectiveTestComponent));
@@ -281,4 +329,14 @@ describe('LetDirective', () => {
       expect(componentNativeElement.textContent).toBe('true');
     });
   });
+
+  describe('when rendering recursively', () => {
+    beforeEach(waitForAsync(setupLetDirectiveTestRecursionComponent));
+
+    it('should render 2nd emitted value if the observable emits while the view is being rendered', fakeAsync(() => {
+      fixtureLetDirectiveTestComponent.detectChanges();
+      expect(letDirectiveTestComponent).toBeDefined();
+      expect(componentNativeElement.textContent).toBe('1');
+    }));
+  });
 });

modules/component/src/let/let.directive.ts

@@ -94,7 +94,7 @@ export class LetDirective<U> implements OnDestroy {
   // eslint-disable-next-line @typescript-eslint/naming-convention
   static ngTemplateGuard_ngrxLet: 'binding';
 
-  private embeddedView: any;
+  private isEmbeddedViewCreated = false;
   private readonly viewContext: LetViewContext<U | undefined | null> = {
     $implicit: undefined,
     ngrxLet: undefined,
@@ -107,7 +107,7 @@ export class LetDirective<U> implements OnDestroy {
   private readonly resetContextObserver: NextObserver<void> = {
     next: () => {
       // if not initialized no need to set undefined
-      if (this.embeddedView) {
+      if (this.isEmbeddedViewCreated) {
         this.viewContext.$implicit = undefined;
         this.viewContext.ngrxLet = undefined;
         this.viewContext.$error = false;
@@ -117,26 +117,26 @@ export class LetDirective<U> implements OnDestroy {
   };
   private readonly updateViewContextObserver: Observer<U | null | undefined> = {
     next: (value: U | null | undefined) => {
+      this.viewContext.$implicit = value;
+      this.viewContext.ngrxLet = value;
       // to have init lazy
-      if (!this.embeddedView) {
+      if (!this.isEmbeddedViewCreated) {
         this.createEmbeddedView();
       }
-      this.viewContext.$implicit = value;
-      this.viewContext.ngrxLet = value;
     },
     error: (error: Error) => {
+      this.viewContext.$error = true;
       // to have init lazy
-      if (!this.embeddedView) {
+      if (!this.isEmbeddedViewCreated) {
         this.createEmbeddedView();
       }
-      this.viewContext.$error = true;
     },
     complete: () => {
+      this.viewContext.$complete = true;
       // to have init lazy
-      if (!this.embeddedView) {
+      if (!this.isEmbeddedViewCreated) {
         this.createEmbeddedView();
       }
-      this.viewContext.$complete = true;
     },
   };
 
@@ -169,7 +169,8 @@ export class LetDirective<U> implements OnDestroy {
   }
 
   createEmbeddedView() {
-    this.embeddedView = this.viewContainerRef.createEmbeddedView(
+    this.isEmbeddedViewCreated = true;
+    this.viewContainerRef.createEmbeddedView(
       this.templateRef,
       this.viewContext
     );