Fixed issue while retrieve undefined item's bitstreams on ItemDetailPreviewComponent

src/app/core/data/bitstream-data.service.ts

@@ -3,7 +3,7 @@ import { Injectable } from '@angular/core';
 import { Store } from '@ngrx/store';
 import { Observable } from 'rxjs/internal/Observable';
 import { map, switchMap } from 'rxjs/operators';
-import { hasValue } from '../../shared/empty.util';
+import { hasValue, isNotEmpty } from '../../shared/empty.util';
 import { NotificationsService } from '../../shared/notifications/notifications.service';
 import { FollowLinkConfig } from '../../shared/utils/follow-link-config.model';
 import { dataService } from '../cache/builders/build-decorators';
@@ -72,7 +72,7 @@ export class BitstreamDataService extends DataService<Bitstream> {
   public getThumbnailFor(item: Item): Observable<RemoteData<Bitstream>> {
     return this.bundleService.findByItemAndName(item, 'THUMBNAIL').pipe(
       switchMap((bundleRD: RemoteData<Bundle>) => {
-        if (hasValue(bundleRD.payload)) {
+        if (isNotEmpty(bundleRD.payload)) {
           return this.findAllByBundle(bundleRD.payload, { elementsPerPage: 1 }).pipe(
             map((bitstreamRD: RemoteData<PaginatedList<Bitstream>>) => {
               if (hasValue(bitstreamRD.payload) && hasValue(bitstreamRD.payload.page)) {
@@ -108,7 +108,7 @@ export class BitstreamDataService extends DataService<Bitstream> {
   public getMatchingThumbnail(item: Item, bitstreamInOriginal: Bitstream): Observable<RemoteData<Bitstream>> {
     return this.bundleService.findByItemAndName(item, 'THUMBNAIL').pipe(
       switchMap((bundleRD: RemoteData<Bundle>) => {
-        if (hasValue(bundleRD.payload)) {
+        if (isNotEmpty(bundleRD.payload)) {
           return this.findAllByBundle(bundleRD.payload, { elementsPerPage: Number.MAX_SAFE_INTEGER }).pipe(
             map((bitstreamRD: RemoteData<PaginatedList<Bitstream>>) => {
               if (hasValue(bitstreamRD.payload) && hasValue(bitstreamRD.payload.page)) {

src/app/shared/object-detail/my-dspace-result-detail-element/item-detail-preview/item-detail-preview.component.html

@@ -10,9 +10,9 @@
     <div class="row mb-1">
       <div class="col-xs-12 col-md-4">
         <ds-metadata-field-wrapper>
-          <ds-thumbnail [thumbnail]="thumbnail$ | async"></ds-thumbnail>
+          <ds-thumbnail [thumbnail]="this.getThumbnail() | async"></ds-thumbnail>
         </ds-metadata-field-wrapper>
-        <ng-container *ngVar="(bitstreams$ | async) as bitstreams">
+        <ng-container *ngVar="(getFiles() | async) as bitstreams">
           <ds-metadata-field-wrapper [label]="('item.page.files' | translate)">
             <div *ngIf="bitstreams?.length > 0" class="file-section">
               <button class="btn btn-link" *ngFor="let file of bitstreams; let last=last;" (click)="downloadBitstreamFile(file?.uuid)">

src/app/shared/object-detail/my-dspace-result-detail-element/item-detail-preview/item-detail-preview.component.spec.ts

@@ -5,8 +5,8 @@ import { NoopAnimationsModule } from '@angular/platform-browser/animations';
 import { Store } from '@ngrx/store';
 import { TranslateLoader, TranslateModule } from '@ngx-translate/core';
 
-import { of as observableOf } from 'rxjs';
-import { Observable } from 'rxjs/internal/Observable';
+import { Observable, of as observableOf } from 'rxjs';
+
 import { RemoteDataBuildService } from '../../../../core/cache/builders/remote-data-build.service';
 import { ObjectCacheService } from '../../../../core/cache/object-cache.service';
 import { BitstreamDataService } from '../../../../core/data/bitstream-data.service';
@@ -28,7 +28,6 @@ import { HALEndpointServiceStub } from '../../../testing/hal-endpoint-service-st
 import { createSuccessfulRemoteDataObject$ } from '../../../testing/utils';
 import { FileSizePipe } from '../../../utils/file-size-pipe';
 import { FollowLinkConfig } from '../../../utils/follow-link-config.model';
-
 import { TruncatePipe } from '../../../utils/truncate.pipe';
 import { VarDirective } from '../../../utils/var.directive';
 import { ItemDetailPreviewFieldComponent } from './item-detail-preview-field/item-detail-preview-field.component';
@@ -127,8 +126,17 @@ describe('ItemDetailPreviewComponent', () => {
 
   }));
 
-  it('should init thumbnail and bitstreams on init', () => {
-    expect(component.thumbnail$).toBeDefined();
-    expect(component.bitstreams$).toBeDefined();
+  it('should get item thumbnail', (done) => {
+    component.getThumbnail().subscribe((thumbnail) => {
+      expect(thumbnail).toBeDefined();
+      done();
+    });
+  });
+
+  it('should get item bitstreams', (done) => {
+    component.getFiles().subscribe((bitstreams) => {
+      expect(bitstreams).toBeDefined();
+      done();
+    })
   });
 });

src/app/shared/object-detail/my-dspace-result-detail-element/item-detail-preview/item-detail-preview.component.ts

@@ -1,17 +1,13 @@
 import { Component, Input } from '@angular/core';
 
 import { Observable } from 'rxjs';
-import { first, map } from 'rxjs/operators';
+import { first } from 'rxjs/operators';
 import { BitstreamDataService } from '../../../../core/data/bitstream-data.service';
-import { RemoteData } from '../../../../core/data/remote-data';
 
 import { Item } from '../../../../core/shared/item.model';
 import {
-  getAllSucceededRemoteListPayload,
   getFirstSucceededRemoteDataPayload,
-  getFirstSucceededRemoteListPayload,
-  getRemoteDataPayload,
-  getSucceededRemoteData
+  getFirstSucceededRemoteListPayload
 } from '../../../../core/shared/operators';
 import { MyDspaceItemStatusType } from '../../../object-collection/shared/mydspace-item-status/my-dspace-item-status-type';
 import { fadeInOut } from '../../../animations/fade';
@@ -71,20 +67,13 @@ export class ItemDetailPreviewComponent {
    *
    * @param {FileService} fileService
    * @param {HALEndpointService} halService
+   * @param {BitstreamDataService} bitstreamDataService
    */
   constructor(private fileService: FileService,
               private halService: HALEndpointService,
               private bitstreamDataService: BitstreamDataService) {
   }
 
-  /**
-   * Initialize all instance variables
-   */
-  ngOnInit() {
-    this.thumbnail$ = this.getThumbnail();
-    this.bitstreams$ = this.getFiles();
-  }
-
   /**
    * Perform bitstream download
    */
@@ -98,14 +87,14 @@ export class ItemDetailPreviewComponent {
   }
 
   // TODO refactor this method to return RemoteData, and the template to deal with loading and errors
-  getThumbnail(): Observable<Bitstream> {
+  public getThumbnail(): Observable<Bitstream> {
     return this.bitstreamDataService.getThumbnailFor(this.item).pipe(
       getFirstSucceededRemoteDataPayload()
     );
   }
 
   // TODO refactor this method to return RemoteData, and the template to deal with loading and errors
-  getFiles(): Observable<Bitstream[]> {
+  public getFiles(): Observable<Bitstream[]> {
     return this.bitstreamDataService
       .findAllByItemAndBundleName(this.item, 'ORIGINAL', { elementsPerPage: Number.MAX_SAFE_INTEGER })
       .pipe(