feat(aio): lazy-load embedded components (#18428)

Fixes #16127

PR Close #18428

aio/src/testing/doc-viewer-utils.ts

@@ -0,0 +1,85 @@
+import { Component, ComponentRef, NgModule, ViewChild } from '@angular/core';
+import { Title } from '@angular/platform-browser';
+
+import { Observable } from 'rxjs/Observable';
+
+import { DocumentContents } from 'app/documents/document.service';
+import { EmbedComponentsService } from 'app/embed-components/embed-components.service';
+import { DocViewerComponent } from 'app/layout/doc-viewer/doc-viewer.component';
+import { Logger } from 'app/shared/logger.service';
+import { TocService } from 'app/shared/toc.service';
+import { MockLogger } from 'testing/logger.service';
+
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+/// `TestDocViewerComponent` (for exposing internal `DocViewerComponent` methods as public).     ///
+/// Only used for type-casting; the actual implementation is irrelevant.                         ///
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+export class TestDocViewerComponent extends DocViewerComponent {
+  embeddedComponentRefs: ComponentRef<any>[];
+
+  addTitleAndToc(docId: string): void { return null as any; }
+  destroyEmbeddedComponents(): void { return null as any; }
+  render(doc: DocumentContents): Observable<void> { return null as any; }
+}
+
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+/// `TestModule` and `TestParentComponent`.                                                      ///
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+// Test parent component.
+@Component({
+  selector: 'aio-test',
+  template: '<aio-doc-viewer [doc]="currentDoc">Test Component</aio-doc-viewer>',
+})
+export class TestParentComponent {
+  currentDoc: DocumentContents;
+  @ViewChild(DocViewerComponent) docViewer: DocViewerComponent;
+}
+
+// Mock services.
+export class MockEmbedComponentsService {
+  embedInto = jasmine.createSpy('EmbedComponentsService#embedInto');
+}
+
+export class MockTitle {
+  setTitle = jasmine.createSpy('Title#reset');
+}
+
+export class MockTocService {
+  genToc = jasmine.createSpy('TocService#genToc');
+  reset = jasmine.createSpy('TocService#reset');
+}
+
+@NgModule({
+  declarations: [
+    DocViewerComponent,
+    TestParentComponent,
+  ],
+  providers: [
+    { provide: Logger, useClass: MockLogger },
+    { provide: EmbedComponentsService, useClass: MockEmbedComponentsService },
+    { provide: Title, useClass: MockTitle },
+    { provide: TocService, useClass: MockTocService },
+  ],
+})
+export class TestModule { }
+
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+/// An observable with spies to test subscribing/unsubscribing.                                  ///
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+export class ObservableWithSubscriptionSpies<T = void> extends Observable<T> {
+  unsubscribeSpies: jasmine.Spy[] = [];
+  subscribeSpy = spyOn(this, 'subscribe').and.callFake((...args) => {
+    const subscription = super.subscribe(...args);
+    const unsubscribeSpy = spyOn(subscription, 'unsubscribe').and.callThrough();
+    this.unsubscribeSpies.push(unsubscribeSpy);
+    return subscription;
+  });
+
+  constructor(subscriber = () => undefined) { super(subscriber); }
+}