Add filtering empty VOs

src/app/user.service.ts

 import { Injectable } from '@angular/core';
 import { HttpClient, HttpErrorResponse } from '@angular/common/http';
 import { throwError as observableThrowError,  Observable, BehaviorSubject, of, EMPTY } from 'rxjs';
-import { map, catchError } from 'rxjs/operators';
+import { map, catchError, combineLatest } from 'rxjs/operators';
 
 import { CookieService } from 'ngx-cookie-service';
 import { StompConfig, StompRService } from '@stomp/ng2-stompjs';
@@ -9,6 +9,7 @@ import { Message } from '@stomp/stompjs';
 
 import { SnackBarService } from './snackbar.service';
 import { IdpService } from './idp.service';
+import { PreferencesService, Prefs } from './preferences/preferences.service';
 
 import {
   VO, User, Update, State, Deployment, DeploymentState, SSHKey, NewSSHKey, IdP, Service, Site, JSONObject
@@ -45,6 +46,7 @@ export class UserService {
     private snackBar: SnackBarService,
     private idpService: IdpService,
     private stompService: StompRService,
+    private prefs: PreferencesService,
   ) {
     this.user$ = new BehaviorSubject(null);
     this.connect();
@@ -368,11 +370,6 @@ export class UserService {
     );
   }
 
-  public subscribeVOs(): Observable<VO[]> {
-    let voSelector = (user: User) => user ? user.vos : [];
-    return this.subscribeSpecific<VO[]>(voSelector);
-  }
-
   public subscribeDeployment(selector: (dep: Deployment) => boolean): Observable<Deployment> {
     return this.subscribeDeployments().pipe(
       map((deployments: Deployment[]) => {
@@ -387,4 +384,28 @@ export class UserService {
   public subscribeServices(): Observable<Service[]> {
     return this.subscribeSpecific(this.serviceSelector);
   }
+
+  public subscribeVOs(): Observable<VO[]> {
+    const voSelector = (user: User) => user ? user.vos : [];
+    const vos$ = this.subscribeSpecific<VO[]>(voSelector);
+    return this.prefs.connect().pipe(
+      combineLatest(
+        vos$,
+        this.subscribeServices(),
+        (prefs: Prefs, vos: VO[], svc: Service[]) => {
+          if (prefs.showEmptyVOs) {
+            // filter VOs that have no services
+            return vos.filter(
+              (vo: VO) => svc.some(
+                (s: Service) => s.vos.some(
+                  svo => svo.id === vo.id,
+                ),
+              ),
+            );
+          }
+          return vos;
+        }
+      )
+    );
+  }
 }