added test and docs for 404 operator

src/app/+collection-page/collection-page.component.ts

@@ -16,11 +16,8 @@ import { Item } from '../core/shared/item.model';
 import { fadeIn, fadeInOut } from '../shared/animations/fade';
 import { hasValue, isNotEmpty } from '../shared/empty.util';
 import { PaginationComponentOptions } from '../shared/pagination/pagination-component-options.model';
-import { combineLatest, filter, first, flatMap, map } from 'rxjs/operators';
-import { SearchService } from '../+search-page/search-service/search.service';
-import { PaginatedSearchOptions } from '../+search-page/paginated-search-options.model';
-import { renderPageNotFoundOn404, toDSpaceObjectListRD } from '../core/shared/operators';
-import { DSpaceObjectType } from '../core/shared/dspace-object-type.model';
+import { filter, first, flatMap, map } from 'rxjs/operators';
+import { redirectToPageNotFoundOn404 } from '../core/shared/operators';
 
 @Component({
   selector: 'ds-collection-page',
@@ -58,7 +55,7 @@ export class CollectionPageComponent implements OnInit, OnDestroy {
   ngOnInit(): void {
     this.collectionRD$ = this.route.data.pipe(
       map((data) => data.collection as RemoteData<Collection>),
-      renderPageNotFoundOn404(this.router),
+      redirectToPageNotFoundOn404(this.router),
       first()
     );
     this.logoRD$ = this.collectionRD$.pipe(

src/app/+collection-page/collection-page.resolver.ts

@@ -19,7 +19,8 @@ export class CollectionPageResolver implements Resolve<RemoteData<Collection>> {
    * Method for resolving a collection based on the parameters in the current route
    * @param {ActivatedRouteSnapshot} route The current ActivatedRouteSnapshot
    * @param {RouterStateSnapshot} state The current RouterStateSnapshot
-   * @returns Observable<<RemoteData<Collection>> Emits the found collection based on the parameters in the current route
+   * @returns Observable<<RemoteData<Collection>> Emits the found collection based on the parameters in the current route,
+   * or an error if something went wrong
    */
   resolve(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Observable<RemoteData<Collection>> {
     return this.collectionService.findById(route.params.id).pipe(

src/app/+community-page/community-page.component.ts

@@ -13,7 +13,7 @@ import { MetadataService } from '../core/metadata/metadata.service';
 
 import { fadeInOut } from '../shared/animations/fade';
 import { hasValue } from '../shared/empty.util';
-import { renderPageNotFoundOn404 } from '../core/shared/operators';
+import { redirectToPageNotFoundOn404 } from '../core/shared/operators';
 
 @Component({
   selector: 'ds-community-page',
@@ -47,7 +47,7 @@ export class CommunityPageComponent implements OnInit {
   ngOnInit(): void {
     this.communityRD$ = this.route.data.pipe(
       map((data) => data.community as RemoteData<Community>),
-      renderPageNotFoundOn404(this.router)
+      redirectToPageNotFoundOn404(this.router)
     );
     this.logoRD$ = this.communityRD$.pipe(
       map((rd: RemoteData<Community>) => rd.payload),

src/app/+community-page/community-page.resolver.ts

@@ -19,11 +19,12 @@ export class CommunityPageResolver implements Resolve<RemoteData<Community>> {
    * Method for resolving a community based on the parameters in the current route
    * @param {ActivatedRouteSnapshot} route The current ActivatedRouteSnapshot
    * @param {RouterStateSnapshot} state The current RouterStateSnapshot
-   * @returns Observable<<RemoteData<Community>> Emits the found community based on the parameters in the current route
+   * @returns Observable<<RemoteData<Community>> Emits the found community based on the parameters in the current route,
+   * or an error if something went wrong
    */
   resolve(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Observable<RemoteData<Community>> {
     return this.communityService.findById(route.params.id).pipe(
-      find((RD) => hasValue(RD.error) || RD.hasSucceeded),
+      find((RD) => hasValue(RD.error) || RD.hasSucceeded)
     );
   }
 }

src/app/+item-page/item-page.resolver.ts

@@ -1,11 +1,11 @@
 import { Injectable } from '@angular/core';
-import { ActivatedRouteSnapshot, Resolve, Router, RouterStateSnapshot } from '@angular/router';
+import { ActivatedRouteSnapshot, Resolve, RouterStateSnapshot } from '@angular/router';
 import { Observable } from 'rxjs';
 import { RemoteData } from '../core/data/remote-data';
 import { ItemDataService } from '../core/data/item-data.service';
 import { Item } from '../core/shared/item.model';
 import { hasValue } from '../shared/empty.util';
-import { find, map } from 'rxjs/operators';
+import { find } from 'rxjs/operators';
 
 /**
  * This class represents a resolver that requests a specific item before the route is activated
@@ -19,7 +19,8 @@ export class ItemPageResolver implements Resolve<RemoteData<Item>> {
    * Method for resolving an item based on the parameters in the current route
    * @param {ActivatedRouteSnapshot} route The current ActivatedRouteSnapshot
    * @param {RouterStateSnapshot} state The current RouterStateSnapshot
-   * @returns Observable<<RemoteData<Item>> Emits the found item based on the parameters in the current route
+   * @returns Observable<<RemoteData<Item>> Emits the found item based on the parameters in the current route,
+   * or an error if something went wrong
    */
   resolve(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Observable<RemoteData<Item>> {
     return this.itemService.findById(route.params.id)

src/app/+item-page/simple/item-page.component.ts

@@ -14,8 +14,8 @@ import { MetadataService } from '../../core/metadata/metadata.service';
 
 import { fadeInOut } from '../../shared/animations/fade';
 import { hasValue } from '../../shared/empty.util';
+import { redirectToPageNotFoundOn404 } from '../../core/shared/operators';
 import { ItemViewMode } from '../../shared/items/item-type-decorator';
-import { renderPageNotFoundOn404 } from '../../core/shared/operators';
 
 /**
  * This component renders a simple item page.
@@ -61,7 +61,7 @@ export class ItemPageComponent implements OnInit {
   ngOnInit(): void {
     this.itemRD$ = this.route.data.pipe(
       map((data) => data.item as RemoteData<Item>),
-      renderPageNotFoundOn404(this.router)
+      redirectToPageNotFoundOn404(this.router)
     );
     this.metadataService.processRemoteData(this.itemRD$);
     this.thumbnail$ = this.itemRD$.pipe(

src/app/core/shared/operators.spec.ts

@@ -13,9 +13,11 @@ import {
   getRequestFromRequestUUID,
   getResourceLinksFromResponse,
   getResponseFromEntry,
-  getSucceededRemoteData
+  getSucceededRemoteData, redirectToPageNotFoundOn404
 } from './operators';
 import { RemoteData } from '../data/remote-data';
+import { RemoteDataError } from '../data/remote-data-error';
+import { of as observableOf } from 'rxjs';
 
 describe('Core Module - RxJS Operators', () => {
   let scheduler: TestScheduler;
@@ -193,6 +195,34 @@ describe('Core Module - RxJS Operators', () => {
     });
   });
 
+  describe('redirectToPageNotFoundOn404', () => {
+    let router;
+    beforeEach(() => {
+      router = jasmine.createSpyObj('router', ['navigateByUrl']);
+    });
+
+    it('should call navigateByUrl to a 404 page, when the remote data contains a 404 error', () => {
+      const testRD = new RemoteData(false, false, false, new RemoteDataError(404, 'Not Found', 'Object was not found'), undefined);
+
+      observableOf(testRD).pipe(redirectToPageNotFoundOn404(router)).subscribe();
+      expect(router.navigateByUrl).toHaveBeenCalledWith('/404', { skipLocationChange: true });
+    });
+
+    it('should not call navigateByUrl to a 404 page, when the remote data contains another error than a 404', () => {
+      const testRD = new RemoteData(false, false, false, new RemoteDataError(500, 'Server Error', 'Something went wrong'), undefined);
+
+      observableOf(testRD).pipe(redirectToPageNotFoundOn404(router)).subscribe();
+      expect(router.navigateByUrl).not.toHaveBeenCalled();
+    });
+
+    it('should not call navigateByUrl to a 404 page, when the remote data contains no error', () => {
+      const testRD = new RemoteData(false, false, true, null, undefined);
+
+      observableOf(testRD).pipe(redirectToPageNotFoundOn404(router)).subscribe();
+      expect(router.navigateByUrl).not.toHaveBeenCalled();
+    });
+  });
+
   describe('getResponseFromEntry', () => {
     it('should return the response for all not empty request entries, when they have a value', () => {
       const source = hot('abcdefg', testRCEs);

src/app/core/shared/operators.ts

@@ -64,7 +64,12 @@ export const getSucceededRemoteData = () =>
   <T>(source: Observable<RemoteData<T>>): Observable<RemoteData<T>> =>
     source.pipe(find((rd: RemoteData<T>) => rd.hasSucceeded));
 
-export const renderPageNotFoundOn404 = (router: Router) =>
+/**
+ * Operator that checks if a remote data object contains a page not found error
+ * When it does contain such an error, it will redirect the user to a page not found, without altering the current URL
+ * @param router The router used to navigate to a new page
+ */
+export const redirectToPageNotFoundOn404 = (router: Router) =>
   <T>(source: Observable<RemoteData<T>>): Observable<RemoteData<T>> =>
     source.pipe(
       tap((rd: RemoteData<T>) => {

src/app/header/header.component.html

@@ -5,7 +5,7 @@
         </a>
 
         <nav class="navbar navbar-light navbar-expand-md float-right px-0">
-            <a href="/search" class="px-1"><i class="fas fa-search fa-lg fa-fw" [title]="'nav.search' | translate"></i></a>
+            <a routerLink="/search" class="px-1"><i class="fas fa-search fa-lg fa-fw" [title]="'nav.search' | translate"></i></a>
             <ds-lang-switch></ds-lang-switch>
             <ds-auth-nav-menu></ds-auth-nav-menu>
             <div class="pl-2">