rx-angular · hoebbelsB · Nov 8, 2022 · Nov 8, 2022 · Nov 25, 2022 · Jan 11, 2023
diff --git a/libs/cdk/template/spec/list-manager.spec.ts b/libs/cdk/template/spec/list-manager.spec.ts
@@ -23,7 +23,7 @@ import {
 } from '@rx-angular/cdk/template';
 import { RxStrategyProvider } from '@rx-angular/cdk/render-strategies';
 import { mockConsole } from '@test-helpers';
-import { ReplaySubject } from 'rxjs';
+import { ReplaySubject, Subject } from 'rxjs';
 
 @Component({
   selector: 'rx-angular-error-test',
@@ -63,6 +63,7 @@ class ListTemplateManagerSpecComponent implements AfterViewInit {
   values$ = new ReplaySubject<number[]>(1);
 
   latestRenderedValue: any;
+  latestRenderedValue$ = new Subject<number>();
 
   constructor(
     private iterableDiffers: IterableDiffers,
@@ -97,6 +98,7 @@ class ListTemplateManagerSpecComponent implements AfterViewInit {
     });
     this.listManager.render(this.values$).subscribe((v: any) => {
       this.latestRenderedValue = v;
+      this.latestRenderedValue$.next(v);
     });
   }
 }
@@ -124,13 +126,7 @@ const customErrorHandler: ErrorHandler = {
 };
 
 let fixtureComponent: any;
-let componentInstance: {
-  listManager: RxListManager<any>;
-  errorHandler: ErrorHandler;
-  templateRef: TemplateRef<any>;
-  values$: ReplaySubject<any[]>;
-  latestRenderedValue: any;
-};
+let componentInstance: ListTemplateManagerSpecComponent;
 let componentNativeElement: any;
 const setupListManagerComponent = (): void => {
   TestBed.configureTestingModule({
@@ -184,6 +180,30 @@ describe('list-manager', () => {
     expect(componentContent).toEqual('1');
   });
 
+  it('should report last rendered value', () => {
+    fixtureComponent.detectChanges();
+    componentInstance.values$.next([1]);
+    fixtureComponent.detectChanges();
+    expect(componentInstance.latestRenderedValue).toEqual([1]);
+  });
+
+  it('should report last rendered value without any changes', () => {
+    let renderedValueUpdate = 0;
+    let renderedValue;
+    componentInstance.latestRenderedValue$.subscribe((value) => {
+      renderedValueUpdate++;
+      renderedValue = value;
+    });
+    const valuesToRender = [1];
+    fixtureComponent.detectChanges();
+    componentInstance.values$.next(valuesToRender);
+    fixtureComponent.detectChanges();
+    componentInstance.values$.next(valuesToRender);
+    fixtureComponent.detectChanges();
+    expect(renderedValue).toEqual([1]);
+    expect(renderedValueUpdate).toBe(2);
+  });
+
   describe('exception handling', () => {
     it('should capture errors with errorHandler', () => {
       fixtureComponent.detectChanges();

diff --git a/libs/cdk/template/src/lib/list-template-manager.ts b/libs/cdk/template/src/lib/list-template-manager.ts
@@ -7,7 +7,13 @@ import {
   TemplateRef,
   TrackByFunction,
 } from '@angular/core';
-import { combineLatest, MonoTypeOperatorFunction, Observable, of } from 'rxjs';
+import {
+  combineLatest,
+  MonoTypeOperatorFunction,
+  NEVER,
+  Observable,
+  of,
+} from 'rxjs';
 import {
   catchError,
   distinctUntilChanged,
@@ -119,8 +125,9 @@ export function createListTemplateManager<
           let changes: IterableChanges<T>;
           if (differ) {
             if (partiallyFinished) {
-              const currentIterable = [];
-              for (let i = 0, ilen = viewContainerRef.length; i < ilen; i++) {
+              const length = viewContainerRef.length;
+              const currentIterable = new Array<T>(viewContainerRef.length);
+              for (let i = 0; i < length; i++) {
                 const viewRef = <EmbeddedViewRef<C>>viewContainerRef.get(i);
                 currentIterable[i] = viewRef.context.$implicit;
               }
@@ -137,7 +144,7 @@ export function createListTemplateManager<
         // Cancel old renders
         switchMap(({ changes, iterable, strategy }) => {
           if (!changes) {
-            return of([]);
+            return of(iterable);
           }
           const values = iterable || [];
           // TODO: we might want to treat other iterables in a more performant way than Array.from()

diff --git a/libs/template/for/src/lib/tests/for.directive.strategy.spec.ts b/libs/template/for/src/lib/tests/for.directive.strategy.spec.ts
@@ -1,6 +1,7 @@
 import { ErrorHandler } from '@angular/core';
 import { ComponentFixture, TestBed } from '@angular/core/testing';
 import { RxStrategyProvider } from '@rx-angular/cdk/render-strategies';
+import { take } from 'rxjs/operators';
 import { ForModule } from '../for.module';
 import { createTestComponent, TestComponent } from './fixtures';
 
@@ -48,7 +49,7 @@ describe('rxFor strategies', () => {
   ])('Strategy: %p', (strategy) => {
     it('should render with given strategy', (done) => {
       component.strategy = strategy;
-      component.renderedValue$.subscribe((v) => {
+      component.renderedValue$.pipe(take(1)).subscribe((v) => {
         expect(v).toEqual([1, 2]);
         expect(nativeElement.textContent).toBe('1;2;');
         done();
@@ -57,7 +58,7 @@ describe('rxFor strategies', () => {
     });
     it('should not affect primary strategy', (done) => {
       component.strategy = strategy;
-      component.renderedValue$.subscribe((v) => {
+      component.renderedValue$.pipe(take(1)).subscribe((v) => {
         expect(v).toEqual([1, 2]);
         expect(nativeElement.textContent).toBe('1;2;');
         expect(strategyProvider.primaryStrategy).toBe(primaryStrategy);