Toggle aria-modal attribute in parent modal when autocomplete panel opens / closes (#27663)

* Toggle parent modal aria-owns attribute when autocomplete is closed

* Add unit tests and update comments

Author: eminguyen

src/material/autocomplete/autocomplete-trigger.ts

@@ -278,6 +278,11 @@ export class MatAutocompleteTrigger
   openPanel(): void {
     this._attachOverlay();
     this._floatLabel();
+    // Add aria-owns attribute when the autocomplete becomes visible.
+    if (this._trackedModal) {
+      const panelId = this.autocomplete.id;
+      addAriaReferencedId(this._trackedModal, 'aria-owns', panelId);
+    }
   }
 
   /** Closes the autocomplete suggestion panel. */
@@ -317,6 +322,12 @@ export class MatAutocompleteTrigger
       // user clicks outside.
       this._changeDetectorRef.detectChanges();
     }
+
+    // Remove aria-owns attribute when the autocomplete is no longer visible.
+    if (this._trackedModal) {
+      const panelId = this.autocomplete.id;
+      removeAriaReferencedId(this._trackedModal, 'aria-owns', panelId);
+    }
   }
 
   /**

src/material/autocomplete/autocomplete.spec.ts

@@ -3729,6 +3729,31 @@ describe('MDC-based MatAutocomplete', () => {
         .withContext('expecting modal to own the autocommplete panel')
         .toContain(panelId);
     }));
+
+    it('should remove the aria-owns attribute of the modal when the autocomplete panel closes', fakeAsync(() => {
+      fixture.componentInstance.trigger.openPanel();
+      fixture.componentInstance.trigger.closePanel();
+      fixture.detectChanges();
+
+      const panelId = fixture.componentInstance.autocomplete.id;
+      const modalElement = fixture.componentInstance.modal.nativeElement;
+
+      expect(modalElement.getAttribute('aria-owns')).toBeFalsy();
+    }));
+
+    it('should readd the aria-owns attribute of the modal when the autocomplete panel opens again', fakeAsync(() => {
+      fixture.componentInstance.trigger.openPanel();
+      fixture.componentInstance.trigger.closePanel();
+      fixture.componentInstance.trigger.openPanel();
+      fixture.detectChanges();
+
+      const panelId = fixture.componentInstance.autocomplete.id;
+      const modalElement = fixture.componentInstance.modal.nativeElement;
+
+      expect(modalElement.getAttribute('aria-owns')?.split(' '))
+        .withContext('expecting modal to own the autocommplete panel')
+        .toContain(panelId);
+    }));
   });
 });