fix(cdk/overlay): expose currently open overlays (#33768)

Adds the `getAttachedOverlays` function that allows users to check which overlays are open at the moment.

Author: crisbeto

goldens/cdk/overlay/index.api.md

@@ -332,6 +332,9 @@ export class FullscreenOverlayContainer extends OverlayContainer implements OnDe
     static ɵprov: i0.ɵɵInjectableDeclaration<FullscreenOverlayContainer>;
 }
 
+// @public
+export function getAttachedOverlays(): OverlayRef[];
+
 // @public
 export class GlobalPositionStrategy implements PositionStrategy {
     apply(): void;

src/cdk/overlay/overlay-ref.ts

@@ -37,6 +37,13 @@ export function isElement(value: any): value is Element {
   return value && (value as Element).nodeType === 1;
 }
 
+const attachedOverlays = new Set<OverlayRef>();
+
+/** Gets all overlays that are currently attached. */
+export function getAttachedOverlays(): OverlayRef[] {
+  return Array.from(attachedOverlays);
+}
+
 /**
  * Reference to an overlay that has been created with the Overlay service.
  * Used to manipulate or dispose of said overlay.
@@ -142,6 +149,7 @@ export class OverlayRef implements PortalOutlet {
     this._updateStackingOrder();
     this._updateElementSize();
     this._updateElementDirection();
+    attachedOverlays.add(this);
 
     if (this._scrollStrategy) {
       this._scrollStrategy.enable();
@@ -248,6 +256,7 @@ export class OverlayRef implements PortalOutlet {
     this._detachContentWhenEmpty();
     this._locationChanges.unsubscribe();
     this._outsideClickDispatcher.remove(this);
+    attachedOverlays.delete(this);
     return detachmentResult;
   }
 
@@ -284,6 +293,7 @@ export class OverlayRef implements PortalOutlet {
     this._detachments.complete();
     this._completeDetachContent();
     this._disposed = true;
+    attachedOverlays.delete(this);
   }
 
   /** Whether the overlay has attached content. */

src/cdk/overlay/overlay.spec.ts

@@ -29,6 +29,7 @@ import {
   PositionStrategy,
   ScrollStrategy,
   createOverlayRef,
+  getAttachedOverlays,
 } from './index';
 
 describe('Overlay', () => {
@@ -478,6 +479,28 @@ describe('Overlay', () => {
     expect(document.querySelector('.cdk-overlay-pane')).toBeFalsy();
   });
 
+  it('should track when an overlay is attached and detached', () => {
+    const overlayRef = createOverlayRef(injector);
+    expect(getAttachedOverlays()).toEqual([]);
+
+    overlayRef.attach(componentPortal);
+    expect(getAttachedOverlays()).toEqual([overlayRef]);
+
+    overlayRef.detach();
+    expect(getAttachedOverlays()).toEqual([]);
+  });
+
+  it('should track when an overlay is attached and disposed', () => {
+    const overlayRef = createOverlayRef(injector);
+    expect(getAttachedOverlays()).toEqual([]);
+
+    overlayRef.attach(componentPortal);
+    expect(getAttachedOverlays()).toEqual([overlayRef]);
+
+    overlayRef.dispose();
+    expect(getAttachedOverlays()).toEqual([]);
+  });
+
   describe('positioning', () => {
     let config: OverlayConfig;
 

src/cdk/overlay/public-api.ts

@@ -20,7 +20,7 @@ export {
   CDK_CONNECTED_OVERLAY_DEFAULT_CONFIG,
 } from './overlay-directives';
 export {FullscreenOverlayContainer} from './fullscreen-overlay-container';
-export {OverlayRef, OverlaySizeConfig} from './overlay-ref';
+export {OverlayRef, OverlaySizeConfig, getAttachedOverlays} from './overlay-ref';
 export {ViewportRuler} from '../scrolling';
 export {ComponentType} from '../portal';
 export {OverlayPositionBuilder} from './position/overlay-position-builder';