119276: Fixed search service first emitting cached stale values instead of waiting for non-stale response

This was problematic for the places that used getFist operators. This is because they only emit data once, and the first value could be the old cached value

Author: alexandrevryghem

src/app/core/shared/search/search.service.ts

@@ -1,7 +1,7 @@
 /* eslint-disable max-classes-per-file */
 import { combineLatest as observableCombineLatest, Observable } from 'rxjs';
 import { Injectable, OnDestroy } from '@angular/core';
-import { map, switchMap, take } from 'rxjs/operators';
+import { map, switchMap, take, skipWhile } from 'rxjs/operators';
 import { FollowLinkConfig } from '../../../shared/utils/follow-link-config.model';
 import { ResponseParsingService } from '../../data/parsing.service';
 import { RemoteData } from '../../data/remote-data';
@@ -140,6 +140,7 @@ export class SearchService implements OnDestroy {
   search<T extends DSpaceObject>(searchOptions?: PaginatedSearchOptions, responseMsToLive?: number, useCachedVersionIfAvailable = true, reRequestOnStale = true, ...linksToFollow: FollowLinkConfig<T>[]): Observable<RemoteData<SearchObjects<T>>> {
     const href$ = this.getEndpoint(searchOptions);
 
+    let startTime: number;
     href$.pipe(
       take(1),
       map((href: string) => {
@@ -163,14 +164,21 @@ export class SearchService implements OnDestroy {
         searchOptions: searchOptions
       });
 
+      startTime = new Date().getTime();
       this.requestService.send(request, useCachedVersionIfAvailable);
     });
 
     const sqr$ = href$.pipe(
       switchMap((href: string) => this.rdb.buildFromHref<SearchObjects<T>>(href))
     );
 
-    return this.directlyAttachIndexableObjects(sqr$, useCachedVersionIfAvailable, reRequestOnStale, ...linksToFollow);
+    return this.directlyAttachIndexableObjects(sqr$, useCachedVersionIfAvailable, reRequestOnStale, ...linksToFollow).pipe(
+      // This skip ensures that if a stale object is present in the cache when you do a
+      // call it isn't immediately returned, but we wait until the remote data for the new request
+      // is created. If useCachedVersionIfAvailable is false it also ensures you don't get a
+      // cached completed object
+      skipWhile((rd: RemoteData<SearchObjects<T>>) => rd.isStale || (!useCachedVersionIfAvailable && rd.lastUpdated < startTime)),
+    );
   }
 
   /**
@@ -291,9 +299,16 @@ export class SearchService implements OnDestroy {
         return FacetValueResponseParsingService;
       }
     });
+    const startTime = new Date().getTime();
     this.requestService.send(request, useCachedVersionIfAvailable);
 
-    return this.rdb.buildFromHref(href);
+    return this.rdb.buildFromHref(href).pipe(
+      // This skip ensures that if a stale object is present in the cache when you do a
+      // call it isn't immediately returned, but we wait until the remote data for the new request
+      // is created. If useCachedVersionIfAvailable is false it also ensures you don't get a
+      // cached completed object
+      skipWhile((rd: RemoteData<FacetValues>) => rd.isStale || (!useCachedVersionIfAvailable && rd.lastUpdated < startTime)),
+    );
   }
 
   /**