fix(quick-filter): Fixes an issue where an ECAC error was thrown.

Fixes an expression changed after checked error that was thrown in the filter field.
Thank you @areknow for pointing that out and helping us investigate.

Fixes dynatrace-oss#1305

libs/barista-components/experimental/quick-filter/src/quick-filter.spec.ts

@@ -101,7 +101,7 @@ describe('dt-quick-filter', () => {
       );
     });
 
-    it('should set the filters on the filter field if they are set on the quick-filter', () => {
+    it('should set the filters on the filter field if they are set on the quick-filter', fakeAsync(() => {
       expect(quickFilterInstance.filters).toHaveLength(0);
       const filters = [
         [
@@ -111,9 +111,10 @@ describe('dt-quick-filter', () => {
       ];
 
       quickFilterInstance.filters = filters;
-      fixture.detectChanges();
+      zone.simulateZoneExit();
+
       expect(filterFieldInstance.filters).toMatchObject(filters);
-    });
+    }));
 
     it('should reset the filters if the data source gets switched', () => {
       quickFilterInstance.filters = [
@@ -156,13 +157,16 @@ describe('dt-quick-filter', () => {
       expect(groups).toMatchObject(['AUT', 'USA']);
     });
 
-    it('should dispatch an event with the changes on selecting an option', () => {
+    it('should dispatch an event with the changes on selecting an option', fakeAsync(() => {
       const changeSpy = jest.spyOn(fixture.componentInstance, 'filterChanges');
       expect(changeSpy).toHaveBeenCalledTimes(0);
       const checkboxes = fixture.debugElement
         .queryAll(By.directive(DtCheckbox))
         .map((el) => el.query(By.css('label')));
 
+      // Zone must be stable at least once before the quickfilter can be interacted with.
+      zone.simulateZoneExit();
+
       dispatchMouseEvent(checkboxes[1].nativeElement, 'click');
       fixture.detectChanges();
 
@@ -174,7 +178,7 @@ describe('dt-quick-filter', () => {
         ],
       ]);
       changeSpy.mockClear();
-    });
+    }));
 
     it('should propagate currentFilterChanges event when emitted on the filter field', fakeAsync(() => {
       const spy = jest.fn();

libs/barista-components/experimental/quick-filter/src/quick-filter.ts

@@ -168,9 +168,18 @@ export class DtQuickFilter<T = any> implements AfterViewInit, OnDestroy {
 
   /** Angular life-cycle hook that will be called after the view is initialized */
   ngAfterViewInit(): void {
-    // When the filters changes apply them to the filter field
-    this._activeFilters$
-      .pipe(takeUntil(this._destroy$))
+    // We need to wait for the first on stable call, otherwise the
+    // underlying filterfield will thow an expression changed after checked
+    // error. Deferring the first filter setting.
+    // Relates to a very weird and hard to reproduce bug described in
+    // https://github.com/dynatrace-oss/barista/issues/1305
+    this._zone.onStable
+      .pipe(
+        take(1),
+        switchMap(() => this._activeFilters$),
+        takeUntil(this._destroy$),
+      )
+      // When the filters changes apply them to the filter field
       .subscribe((filters) => {
         if (this._filterField.filters !== filters) {
           this._filterField.filters = filters;