Notifications: Prevent triggering duplicate notifications (#114497)

* fix(notifications): prevent event listener re-registration on route changes

* refactor(notifications): rename alert handling functions for clarity

* refactor(notifications): simplify alert handling by using spread operator for payloads

* refactor(events): address feedback - update LegacyEmitter and LegacyEventHandler interfaces for improved type safety

* fix(events): ensure event handlers handle undefined events gracefully in tests

* test(notifications): add tests for event listener registration and cleanup in AppNotificationList

packages/grafana-data/src/events/EventBus.test.ts

@@ -91,8 +91,10 @@ describe('EventBus', () => {
     it('Supports legacy events', () => {
       const bus = new EventBusSrv();
       const events: LegacyEventPayload[] = [];
-      const handler = (event: LegacyEventPayload) => {
-        events.push(event);
+      const handler = (event?: LegacyEventPayload) => {
+        if (event) {
+          events.push(event);
+        }
       };
 
       bus.on(legacyEvent, handler);
@@ -111,7 +113,9 @@ describe('EventBus', () => {
       const newEvents: AlertSuccessEvent[] = [];
 
       bus.on(legacyEvent, (event) => {
-        legacyEvents.push(event);
+        if (event) {
+          legacyEvents.push(event);
+        }
       });
 
       bus.subscribe(AlertSuccessEvent, (event) => {

packages/grafana-data/src/events/types.ts

@@ -133,12 +133,12 @@ export interface LegacyEmitter {
   /**
    * @deprecated use $on
    */
-  off<T>(event: AppEvent<T> | string, handler: (payload?: T) => void): void;
+  off<T>(event: AppEvent<T> | string, handler: LegacyEventHandler<T>): void;
 }
 
 /** @public */
 export interface LegacyEventHandler<T> {
-  (payload: T): void;
+  (payload?: T): void;
   wrapper?: (event: BusEvent) => void;
 }