[CST-4510] Fix issue with multiple selection in the collection-dropdown.component

src/app/shared/collection-dropdown/collection-dropdown.component.html

@@ -18,9 +18,10 @@
      [scrollWindow]="false"
      (scrolled)="onScrollDown()">
 
-  <button class="dropdown-item disabled" *ngIf="searchListCollection?.length == 0 && !(isLoadingList | async)">
+  <button class="dropdown-item disabled" *ngIf="searchListCollection?.length == 0 && !(isLoading | async)">
     {{'submission.sections.general.no-collection' | translate}}
   </button>
+  <ng-container *ngIf="searchListCollection?.length > 0 && !(isLoading | async)">
     <button *ngFor="let listItem of searchListCollection"
             class="dropdown-item collection-item"
             title="{{ listItem.collection.name }}"
@@ -32,7 +33,8 @@
         <li class="list-item text-truncate text-primary font-weight-bold">{{ listItem.collection.name}}</li>
       </ul>
     </button>
-  <button class="dropdown-item disabled" *ngIf="(isLoadingList | async)">
+  </ng-container>
+  <button class="dropdown-item disabled" *ngIf="(isLoading | async)">
     <ds-loading message="{{'loading.default' | translate}}">
     </ds-loading>
   </button>

src/app/shared/collection-dropdown/collection-dropdown.component.spec.ts

@@ -108,9 +108,6 @@ describe('CollectionDropdownComponent', () => {
   const paginatedCollection = buildPaginatedList(new PageInfo(), collections);
   const paginatedCollectionRD$ = createSuccessfulRemoteDataObject$(paginatedCollection);
 
-  const paginatedEmptyCollection = buildPaginatedList(new PageInfo(), []);
-  const paginatedEmptyCollectionRD$ = createSuccessfulRemoteDataObject$(paginatedEmptyCollection);
-
   const paginatedOneElementCollection = buildPaginatedList(new PageInfo(), [collections[0]]);
   const paginatedOneElementCollectionRD$ = createSuccessfulRemoteDataObject$(paginatedOneElementCollection);
 
@@ -203,10 +200,10 @@ describe('CollectionDropdownComponent', () => {
   });
 
   it('should change loader status', () => {
-    spyOn(component.isLoadingList, 'next').and.callThrough();
+    spyOn(component.isLoading, 'next').and.callThrough();
     component.hideShowLoader(true);
 
-    expect(component.isLoadingList.next).toHaveBeenCalledWith(true);
+    expect(component.isLoading.next).toHaveBeenCalledWith(true);
   });
 
   it('reset pagination fields', () => {

src/app/shared/collection-dropdown/collection-dropdown.component.ts

@@ -87,10 +87,10 @@ export class CollectionDropdownComponent implements OnInit, OnDestroy {
   /**
    * A boolean representing if the loader is visible or not
    */
-  isLoadingList: BehaviorSubject<boolean> = new BehaviorSubject(false);
+  isLoading: BehaviorSubject<boolean> = new BehaviorSubject(false);
 
   /**
-   * A numeric representig current page
+   * A numeric representing current page
    */
   currentPage: number;
 
@@ -100,7 +100,7 @@ export class CollectionDropdownComponent implements OnInit, OnDestroy {
   hasNextPage: boolean;
 
   /**
-   * Current seach query used to filter collection list
+   * Current search query used to filter collection list
    */
   currentQuery: string;
 
@@ -145,6 +145,7 @@ export class CollectionDropdownComponent implements OnInit, OnDestroy {
    * Initialize collection list
    */
   ngOnInit() {
+    this.isLoading.next(false);
     this.subs.push(this.searchField.valueChanges.pipe(
         debounceTime(500),
         distinctUntilChanged(),
@@ -173,7 +174,7 @@ export class CollectionDropdownComponent implements OnInit, OnDestroy {
   }
 
   /**
-   * Method used from infitity scroll for retrive more data on scroll down
+   * Method used from infinity scroll for retrieve more data on scroll down
    */
   onScrollDown() {
     if ( this.hasNextPage ) {
@@ -188,6 +189,7 @@ export class CollectionDropdownComponent implements OnInit, OnDestroy {
    *    the selected [CollectionListEntry]
    */
   onSelect(event: CollectionListEntry) {
+    this.isLoading.next(true);
     this.selectionChange.emit(event);
   }
 
@@ -197,13 +199,13 @@ export class CollectionDropdownComponent implements OnInit, OnDestroy {
    * @param page page number
    */
   populateCollectionList(query: string, page: number) {
-    this.isLoadingList.next(true);
+    this.isLoading.next(true);
     // Set the pagination info
     const findOptions: FindListOptions = {
       elementsPerPage: 10,
       currentPage: page
     };
-    let searchListService$: Observable<RemoteData<PaginatedList<Collection>>> = null;
+    let searchListService$: Observable<RemoteData<PaginatedList<Collection>>>;
     if (this.entityType) {
       searchListService$ = this.collectionDataService
       .getAuthorizedCollectionByEntityType(
@@ -279,7 +281,7 @@ export class CollectionDropdownComponent implements OnInit, OnDestroy {
    * @param hideShow true for show, false otherwise
    */
   hideShowLoader(hideShow: boolean) {
-    this.isLoadingList.next(hideShow);
+    this.isLoading.next(hideShow);
   }
 
   /**

src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/external-source-tab/external-source-entry-import-modal/external-source-entry-import-modal.component.ts

@@ -18,7 +18,7 @@ import { ListableObject } from '../../../../../../object-collection/shared/lista
 import { ItemDataService } from '../../../../../../../core/data/item-data.service';
 import { PaginationComponentOptions } from '../../../../../../pagination/pagination-component-options.model';
 import { getFirstSucceededRemoteData, getRemoteDataPayload } from '../../../../../../../core/shared/operators';
-import { mergeMap, take } from 'rxjs/operators';
+import { switchMap, take } from 'rxjs/operators';
 import { ItemSearchResult } from '../../../../../../object-collection/shared/item-search-result.model';
 import { NotificationsService } from '../../../../../../notifications/notifications.service';
 import { TranslateService } from '@ngx-translate/core';
@@ -219,7 +219,7 @@ export class ExternalSourceEntryImportModalComponent implements OnInit {
     this.modalRef.componentInstance.entityType = this.relatedEntityType.label;
 
     this.modalRef.componentInstance.selectedEvent.pipe(
-      mergeMap((collectionListEntry: CollectionListEntry) => {
+      switchMap((collectionListEntry: CollectionListEntry) => {
         return this.itemService.importExternalSourceEntry(this.externalSourceEntry, collectionListEntry.collection.id).pipe(
           getFirstSucceededRemoteData(),
           getRemoteDataPayload(),