[Dashboard] Fix for controls selections causing multiple fetches (#224761)

Prevents Dashboard from firing two requests when a Control change is made.

src/platform/plugins/shared/dashboard/public/dashboard_api/search_sessions/new_session.test.ts

@@ -9,7 +9,7 @@
 
 import type { DataViewFieldBase, DataViewBase, TimeRange, Filter } from '@kbn/es-query';
 import { buildExistsFilter, disableFilter, pinFilter, toggleFilterNegated } from '@kbn/es-query';
-import { BehaviorSubject } from 'rxjs';
+import { BehaviorSubject, Observable } from 'rxjs';
 import { newSession$ } from './new_session';
 
 describe('newSession$', () => {
@@ -56,6 +56,21 @@ describe('newSession$', () => {
       subscription.unsubscribe();
     });
 
+    test('should fire on filter change when reload has not yet been called', async () => {
+      const reloadApi = { ...api, reload$: new Observable<void>() };
+      filters$.next([existsFilter]);
+
+      let count = 0;
+      const subscription = newSession$(reloadApi).subscribe(() => {
+        count++;
+      });
+
+      filters$.next([toggleFilterNegated(existsFilter)]);
+      await new Promise((resolve) => setTimeout(resolve, 0));
+      expect(count).toBe(1);
+      subscription.unsubscribe();
+    });
+
     test('should not fire on disabled filter change', async () => {
       const disabledFilter = disableFilter(existsFilter);
       filters$.next([disabledFilter]);

src/platform/plugins/shared/dashboard/public/dashboard_api/search_sessions/new_session.ts

@@ -8,7 +8,7 @@
  */
 
 import { COMPARE_ALL_OPTIONS, Filter, TimeRange, onlyDisabledFiltersChanged } from '@kbn/es-query';
-import { combineLatest, distinctUntilChanged, Observable, skip } from 'rxjs';
+import { combineLatest, distinctUntilChanged, Observable, skip, startWith } from 'rxjs';
 import { apiPublishesSettings } from '@kbn/presentation-containers/interfaces/publishes_settings';
 import { apiPublishesReload, apiPublishesUnifiedSearch } from '@kbn/presentation-publishing';
 import { areTimesEqual } from '../unified_search_manager';
@@ -61,7 +61,7 @@ export function newSession$(api: unknown) {
   }
 
   if (apiPublishesReload(api)) {
-    observables.push(api.reload$);
+    observables.push(api.reload$.pipe(startWith(undefined)));
   }
 
   return combineLatest(observables).pipe(skip(1));

src/platform/plugins/shared/dashboard/public/dashboard_api/unified_search_manager.ts

@@ -145,7 +145,6 @@ export function initializeUnifiedSearchManager(
       }
     )
   );
-  controlGroupSubscriptions.add(controlGroupFilters$.subscribe(() => panelsReload$.next()));
   controlGroupSubscriptions.add(
     controlGroupTimeslice$.subscribe((timeslice) => {
       if (timeslice !== timeslice$.value) timeslice$.next(timeslice);