fix(autocomplete): panelClosingActions emitting when tabbing away from a closed autocomplete

Fixes the `MatAutocompleteTrigger.panelClosingActions` emitting when the user tabs away from an autocomplete that was closed already.

Fixes #8763.

Author: crisbeto

src/lib/autocomplete/autocomplete-trigger.ts

@@ -193,7 +193,7 @@ export class MatAutocompleteTrigger implements ControlValueAccessor, OnDestroy {
   get panelClosingActions(): Observable<MatOptionSelectionChange> {
     return merge(
       this.optionSelections,
-      this.autocomplete._keyManager.tabOut,
+      this.autocomplete._keyManager.tabOut.pipe(filter(() => this._panelOpen)),
       this._escapeEventStream,
       this._outsideClickStream
     );

src/lib/autocomplete/autocomplete.spec.ts

@@ -1370,6 +1370,23 @@ describe('MatAutocomplete', () => {
       });
     }));
 
+    it('should not emit when tabbing away from a closed panel', async(() => {
+      const tabEvent = createKeyboardEvent('keydown', TAB);
+      input.focus();
+
+      fixture.whenStable().then(() => {
+        trigger._handleKeydown(tabEvent);
+
+        // Ensure that it emitted once while the panel was open.
+        expect(closingActionSpy).toHaveBeenCalledTimes(1);
+
+        trigger._handleKeydown(tabEvent);
+
+        // Ensure that it didn't emit again when tabbing out again.
+        expect(closingActionSpy).toHaveBeenCalledTimes(1);
+      });
+    }));
+
     it('should emit panel close event when selecting an option', async(() => {
       fixture.whenStable().then(() => {
         const option = overlayContainerElement.querySelector('mat-option') as HTMLElement;