fix(google-maps): allow ground overlay bounds to be changed

Allows for the bounds of the Google Maps ground overlay to be changed after initialization.
This case is different from other similar components, because Google Maps doesn't
provide an API to change the bounds so we have to recreate the overlay any time
they change.

Fixes #20865.

Author: crisbeto

src/google-maps/map-ground-overlay/map-ground-overlay.spec.ts

@@ -55,13 +55,6 @@ describe('MapGroundOverlay', () => {
     expect(groundOverlaySpy.setMap).toHaveBeenCalledWith(mapSpy);
   });
 
-  it('has an error if required bounds are not provided', () => {
-    expect(() => {
-      const fixture = TestBed.createComponent(TestApp);
-      fixture.detectChanges();
-    }).toThrow(new Error('Image bounds are required'));
-  });
-
   it('exposes methods that provide information about the Ground Overlay', () => {
     const groundOverlaySpy = createGroundOverlaySpy(url, bounds, groundOverlayOptions);
     createGroundOverlayConstructorSpy(groundOverlaySpy).and.callThrough();
@@ -143,6 +136,22 @@ describe('MapGroundOverlay', () => {
     expect(groundOverlaySpy.setMap).toHaveBeenCalledWith(mapSpy);
   });
 
+  it('should recreate the ground overlay when the bounds change', () => {
+    const groundOverlaySpy = createGroundOverlaySpy(url, bounds, groundOverlayOptions);
+    createGroundOverlayConstructorSpy(groundOverlaySpy).and.callThrough();
+
+    const fixture = TestBed.createComponent(TestApp);
+    fixture.detectChanges();
+
+    const oldOverlay = fixture.componentInstance.groundOverlay.groundOverlay;
+    fixture.componentInstance.bounds = {...bounds};
+    fixture.detectChanges();
+
+    const newOverlay = fixture.componentInstance.groundOverlay.groundOverlay;
+    expect(newOverlay).toBeTruthy();
+    expect(newOverlay).not.toBe(oldOverlay);
+  });
+
 });
 
 @Component({

src/google-maps/map-ground-overlay/map-ground-overlay.ts

@@ -11,7 +11,7 @@
 
 import {Directive, Input, NgZone, OnDestroy, OnInit, Output} from '@angular/core';
 import {BehaviorSubject, Observable, Subject} from 'rxjs';
-import {map, take, takeUntil} from 'rxjs/operators';
+import {takeUntil} from 'rxjs/operators';
 
 import {GoogleMap} from '../google-map/google-map';
 import {MapEventManager} from '../map-event-manager';
@@ -30,6 +30,9 @@ export class MapGroundOverlay implements OnInit, OnDestroy {
 
   private readonly _opacity = new BehaviorSubject<number>(1);
   private readonly _url = new BehaviorSubject<string>('');
+  private readonly _bounds =
+      new BehaviorSubject<google.maps.LatLngBounds|google.maps.LatLngBoundsLiteral|undefined>(
+          undefined);
   private readonly _destroyed = new Subject<void>();
 
   /**
@@ -46,7 +49,13 @@ export class MapGroundOverlay implements OnInit, OnDestroy {
   }
 
   /** Bounds for the overlay. */
-  @Input() bounds: google.maps.LatLngBounds|google.maps.LatLngBoundsLiteral;
+  @Input()
+  get bounds(): google.maps.LatLngBounds|google.maps.LatLngBoundsLiteral {
+    return this._bounds.value!;
+  }
+  set bounds(bounds: google.maps.LatLngBounds|google.maps.LatLngBoundsLiteral) {
+    this._bounds.next(bounds);
+  }
 
   /** Whether the overlay is clickable */
   @Input() clickable: boolean = false;
@@ -77,21 +86,30 @@ export class MapGroundOverlay implements OnInit, OnDestroy {
   constructor(private readonly _map: GoogleMap, private readonly _ngZone: NgZone) {}
 
   ngOnInit() {
-    if (!this.bounds && (typeof ngDevMode === 'undefined' || ngDevMode)) {
-      throw Error('Image bounds are required');
-    }
     if (this._map._isBrowser) {
-      this._combineOptions().pipe(take(1)).subscribe(options => {
+      // The ground overlay setup is slightly different from the other Google Maps objects in that
+      // we have to recreate the `GroundOverlay` object whenever the bounds change, because
+      // Google Maps doesn't provide an API to update the bounds of an existing overlay.
+      this._bounds.pipe(takeUntil(this._destroyed)).subscribe(bounds => {
+        if (this.groundOverlay) {
+          this.groundOverlay.setMap(null);
+          this.groundOverlay = undefined;
+        }
+
         // Create the object outside the zone so its events don't trigger change detection.
         // We'll bring it back in inside the `MapEventManager` only for the events that the
         // user has subscribed to.
-        this._ngZone.runOutsideAngular(() => {
-          this.groundOverlay =
-              new google.maps.GroundOverlay(this._url.getValue(), this.bounds, options);
-        });
-        this._assertInitialized();
-        this.groundOverlay.setMap(this._map.googleMap!);
-        this._eventManager.setTarget(this.groundOverlay);
+        if (bounds) {
+          this._ngZone.runOutsideAngular(() => {
+            this.groundOverlay = new google.maps.GroundOverlay(this._url.getValue(), bounds, {
+              clickable: this.clickable,
+              opacity: this._opacity.value,
+            });
+          });
+          this._assertInitialized();
+          this.groundOverlay.setMap(this._map.googleMap!);
+          this._eventManager.setTarget(this.groundOverlay);
+        }
       });
 
       this._watchForOpacityChanges();
@@ -138,19 +156,9 @@ export class MapGroundOverlay implements OnInit, OnDestroy {
     return this.groundOverlay.getUrl();
   }
 
-  private _combineOptions(): Observable<google.maps.GroundOverlayOptions> {
-    return this._opacity.pipe(map(opacity => {
-      const combinedOptions: google.maps.GroundOverlayOptions = {
-        clickable: this.clickable,
-        opacity,
-      };
-      return combinedOptions;
-    }));
-  }
-
   private _watchForOpacityChanges() {
     this._opacity.pipe(takeUntil(this._destroyed)).subscribe(opacity => {
-      if (opacity) {
+      if (opacity != null) {
         this._assertInitialized();
         this.groundOverlay.setOpacity(opacity);
       }

tools/public_api_guard/google-maps/google-maps.d.ts

@@ -113,7 +113,8 @@ export declare class MapCircle implements OnInit, OnDestroy {
 }
 
 export declare class MapGroundOverlay implements OnInit, OnDestroy {
-    bounds: google.maps.LatLngBounds | google.maps.LatLngBoundsLiteral;
+    get bounds(): google.maps.LatLngBounds | google.maps.LatLngBoundsLiteral;
+    set bounds(bounds: google.maps.LatLngBounds | google.maps.LatLngBoundsLiteral);
     clickable: boolean;
     groundOverlay?: google.maps.GroundOverlay;
     mapClick: Observable<google.maps.MouseEvent>;