RED-5224: get stat if doesn't exist

src/lib/services/stats.service.ts

@@ -1,5 +1,5 @@
 import { inject, Injectable } from '@angular/core';
-import { BehaviorSubject, Observable } from 'rxjs';
+import { BehaviorSubject, Observable, switchMap } from 'rxjs';
 import { HttpClient } from '@angular/common/http';
 import { tap } from 'rxjs/operators';
 import { HeadersConfiguration, mapEach, RequiredParam, Validate } from '../utils';
@@ -43,7 +43,12 @@ export abstract class StatsService<E, I = E> {
     }
 
     watch$(key: string): Observable<E> {
-        return this._getBehaviourSubject(key).asObservable();
+        const subject = this.#map.get(key);
+        if (!subject) {
+            return this.getFor([key]).pipe(switchMap(() => this._getBehaviourSubject(key).asObservable()));
+        }
+
+        return subject.asObservable();
     }
 
     private _pluckPrimaryKey(stats: E): string {
@@ -53,7 +58,11 @@ export abstract class StatsService<E, I = E> {
     }
 
     private _getBehaviourSubject(key: string): BehaviorSubject<E> {
-        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
-        return this.#map.get(key)!;
+        const subject = this.#map.get(key);
+        if (!subject) {
+            throw new Error(`No stats for key ${key}`);
+        }
+
+        return subject;
     }
 }