Answer: 11

apps/rxjs/11-high-order-operator-bug/src/app/app.service.ts

@@ -1,5 +1,5 @@
 import { inject, Injectable } from '@angular/core';
-import { merge, Observable, of } from 'rxjs';
+import { catchError, forkJoin, map, Observable, of, tap } from 'rxjs';
 import { LocalDBService, TopicType } from './localDB.service';
 
 @Injectable({ providedIn: 'root' })
@@ -10,10 +10,38 @@ export class AppService {
 
   deleteOldTopics(type: TopicType): Observable<boolean> {
     const infoByType = this.dbService.searchByType(type);
-    return infoByType.length > 0
-      ? infoByType
-          .map((t) => this.dbService.deleteOneTopic(t.id))
-          .reduce((acc, curr) => merge(acc, curr), of(true))
-      : of(true);
+
+    if (!infoByType?.length) {
+      return of(true);
+    }
+
+    const requests$ = infoByType.map((t) =>
+      this.dbService.deleteOneTopic(t.id).pipe(
+        tap((result) => {
+          if (result) {
+            console.log(`${type} with id ${t.id} deleted successfully.`);
+          } else {
+            console.error(`Failed to delete ${type} with id ${t.id}.`);
+          }
+        }),
+        catchError((error) => {
+          console.error(
+            `There was an error while deleting ${type} with id ${t.id}.`,
+            error,
+          );
+          return of(false);
+        }),
+      ),
+    );
+
+    return forkJoin(requests$).pipe(
+      tap((results) =>
+        console.log(
+          `All deletion requests for ${type} completed with results:`,
+          results,
+        ),
+      ),
+      map((results) => results.every((r) => r)),
+    );
   }
 }

apps/rxjs/11-high-order-operator-bug/src/app/localDB.service.ts

@@ -1,7 +1,7 @@
 /* eslint-disable @typescript-eslint/member-ordering */
 import { randomError } from '@angular-challenges/shared/utils';
 import { computed, Injectable, signal } from '@angular/core';
-import { of } from 'rxjs';
+import { Observable, of, throwError } from 'rxjs';
 
 export type TopicType = 'food' | 'book' | 'sport';
 
@@ -42,12 +42,12 @@ export class LocalDBService {
     this.state.set({ infos: this.state().infos.filter((i) => i.id !== id) });
   };
 
-  deleteOneTopic = (id: number) =>
+  deleteOneTopic = (id: number): Observable<boolean> =>
     randomError({
       success: () => {
         this.deleteOne(id);
         return of(true);
       },
-      error: () => of(false),
+      error: () => throwError(() => new Error('Random error occurred')),
     });
 }