fix(overlay): avoid same overlay being added to the keyboard event stack multiple times (#12222)

Author: crisbeto

src/cdk/overlay/keyboard/overlay-keyboard-dispatcher.spec.ts

@@ -157,6 +157,27 @@ describe('OverlayKeyboardDispatcher', () => {
     expect(overlayOneSpy).toHaveBeenCalled();
   });
 
+  it('should not add the same overlay to the stack multiple times', () => {
+    const overlayOne = overlay.create();
+    const overlayTwo = overlay.create();
+    const overlayOneSpy = jasmine.createSpy('overlayOne keyboard event spy');
+    const overlayTwoSpy = jasmine.createSpy('overlayTwo keyboard event spy');
+
+    overlayOne.keydownEvents().subscribe(overlayOneSpy);
+    overlayTwo.keydownEvents().subscribe(overlayTwoSpy);
+
+    keyboardDispatcher.add(overlayOne);
+    keyboardDispatcher.add(overlayTwo);
+    keyboardDispatcher.add(overlayOne);
+
+    dispatchKeyboardEvent(document.body, 'keydown', ESCAPE);
+
+    expect(keyboardDispatcher._attachedOverlays).toEqual([overlayTwo, overlayOne]);
+
+    expect(overlayTwoSpy).not.toHaveBeenCalled();
+    expect(overlayOneSpy).toHaveBeenCalled();
+  });
+
 });
 
 

src/cdk/overlay/keyboard/overlay-keyboard-dispatcher.ts

@@ -42,6 +42,9 @@ export class OverlayKeyboardDispatcher implements OnDestroy {
 
   /** Add a new overlay to the list of attached overlay refs. */
   add(overlayRef: OverlayRef): void {
+    // Ensure that we don't get the same overlay multiple times.
+    this.remove(overlayRef);
+
     // Lazily start dispatcher once first overlay is added
     if (!this._isAttached) {
       this._document.body.addEventListener('keydown', this._keydownListener, true);