fix(google-maps): unable to subscribe to events after initialization

As things are set up right now in the `google-map`, `map-marker` and `map-info-window` components we choose whether to bind an event based on whether there are subscribers to its observable. The problem is that if the user decides to subscribe after init (e.g. by getting a hold of object with `ViewChild` and subscribing) it'll never emit because the native event wasn't added.

These changes fix the issue by switching the event to be observables and binding the event when something has subscribed. I've also introduced a `MapEventManager` class to make it easier to keep track of the events and to avoid duplication between the three components.

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

@@ -1,4 +1,4 @@
-import {Component} from '@angular/core';
+import {Component, ViewChild} from '@angular/core';
 import {async, TestBed} from '@angular/core/testing';
 import {By} from '@angular/platform-browser';
 
@@ -217,28 +217,46 @@ describe('GoogleMap', () => {
     mapSpy = createMapSpy(DEFAULT_OPTIONS);
     createMapConstructorSpy(mapSpy).and.callThrough();
 
+    const addSpy = mapSpy.addListener;
     const fixture = TestBed.createComponent(TestApp);
     fixture.detectChanges();
 
-    expect(mapSpy.addListener).toHaveBeenCalledWith('click', jasmine.any(Function));
-    expect(mapSpy.addListener).toHaveBeenCalledWith('center_changed', jasmine.any(Function));
-    expect(mapSpy.addListener).toHaveBeenCalledWith('rightclick', jasmine.any(Function));
-    expect(mapSpy.addListener).not.toHaveBeenCalledWith('bounds_changed', jasmine.any(Function));
-    expect(mapSpy.addListener).not.toHaveBeenCalledWith('dblclick', jasmine.any(Function));
-    expect(mapSpy.addListener).not.toHaveBeenCalledWith('drag', jasmine.any(Function));
-    expect(mapSpy.addListener).not.toHaveBeenCalledWith('dragend', jasmine.any(Function));
-    expect(mapSpy.addListener).not.toHaveBeenCalledWith('dragstart', jasmine.any(Function));
-    expect(mapSpy.addListener).not.toHaveBeenCalledWith('heading_changed', jasmine.any(Function));
-    expect(mapSpy.addListener).not.toHaveBeenCalledWith('idle', jasmine.any(Function));
-    expect(mapSpy.addListener).not.toHaveBeenCalledWith('maptypeid_changed', jasmine.any(Function));
-    expect(mapSpy.addListener).not.toHaveBeenCalledWith('mousemove', jasmine.any(Function));
-    expect(mapSpy.addListener).not.toHaveBeenCalledWith('mouseout', jasmine.any(Function));
-    expect(mapSpy.addListener).not.toHaveBeenCalledWith('mouseover', jasmine.any(Function));
-    expect(mapSpy.addListener)
-        .not.toHaveBeenCalledWith('projection_changed', jasmine.any(Function));
-    expect(mapSpy.addListener).not.toHaveBeenCalledWith('tilesloaded', jasmine.any(Function));
-    expect(mapSpy.addListener).not.toHaveBeenCalledWith('tilt_changed', jasmine.any(Function));
-    expect(mapSpy.addListener).not.toHaveBeenCalledWith('zoom_changed', jasmine.any(Function));
+    expect(addSpy).toHaveBeenCalledWith('click', jasmine.any(Function));
+    expect(addSpy).toHaveBeenCalledWith('center_changed', jasmine.any(Function));
+    expect(addSpy).toHaveBeenCalledWith('rightclick', jasmine.any(Function));
+    expect(addSpy).not.toHaveBeenCalledWith('bounds_changed', jasmine.any(Function));
+    expect(addSpy).not.toHaveBeenCalledWith('dblclick', jasmine.any(Function));
+    expect(addSpy).not.toHaveBeenCalledWith('drag', jasmine.any(Function));
+    expect(addSpy).not.toHaveBeenCalledWith('dragend', jasmine.any(Function));
+    expect(addSpy).not.toHaveBeenCalledWith('dragstart', jasmine.any(Function));
+    expect(addSpy).not.toHaveBeenCalledWith('heading_changed', jasmine.any(Function));
+    expect(addSpy).not.toHaveBeenCalledWith('idle', jasmine.any(Function));
+    expect(addSpy).not.toHaveBeenCalledWith('maptypeid_changed', jasmine.any(Function));
+    expect(addSpy).not.toHaveBeenCalledWith('mousemove', jasmine.any(Function));
+    expect(addSpy).not.toHaveBeenCalledWith('mouseout', jasmine.any(Function));
+    expect(addSpy).not.toHaveBeenCalledWith('mouseover', jasmine.any(Function));
+    expect(addSpy).not.toHaveBeenCalledWith('projection_changed', jasmine.any(Function));
+    expect(addSpy).not.toHaveBeenCalledWith('tilesloaded', jasmine.any(Function));
+    expect(addSpy).not.toHaveBeenCalledWith('tilt_changed', jasmine.any(Function));
+    expect(addSpy).not.toHaveBeenCalledWith('zoom_changed', jasmine.any(Function));
+  });
+
+  it('should be able to add an event listener after init', () => {
+    mapSpy = createMapSpy(DEFAULT_OPTIONS);
+    createMapConstructorSpy(mapSpy).and.callThrough();
+
+    const addSpy = mapSpy.addListener;
+    const fixture = TestBed.createComponent(TestApp);
+    fixture.detectChanges();
+
+    expect(addSpy).not.toHaveBeenCalledWith('projection_changed', jasmine.any(Function));
+
+    // Pick an event that isn't bound in the template.
+    const subscription = fixture.componentInstance.map.projectionChanged.subscribe();
+    fixture.detectChanges();
+
+    expect(addSpy).toHaveBeenCalledWith('projection_changed', jasmine.any(Function));
+    subscription.unsubscribe();
   });
 });
 
@@ -255,15 +273,14 @@ describe('GoogleMap', () => {
             </google-map>`,
 })
 class TestApp {
+  @ViewChild(GoogleMap) map: GoogleMap;
   height?: string;
   width?: string;
   center?: google.maps.LatLngLiteral;
   zoom?: number;
   options?: google.maps.MapOptions;
 
   handleClick(event: google.maps.MouseEvent) {}
-
   handleCenterChanged() {}
-
   handleRightclick(event: google.maps.MouseEvent) {}
 }

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

@@ -13,7 +13,6 @@ import {
   ChangeDetectionStrategy,
   Component,
   ElementRef,
-  EventEmitter,
   Input,
   OnChanges,
   OnDestroy,
@@ -27,6 +26,7 @@ import {
 import {isPlatformBrowser} from '@angular/common';
 import {BehaviorSubject, combineLatest, Observable, Subject} from 'rxjs';
 import {map, shareReplay, take, takeUntil} from 'rxjs/operators';
+import {MapEventManager} from '../map-event-manager';
 
 interface GoogleMapsWindow extends Window {
   google?: typeof google;
@@ -64,6 +64,20 @@ export const DEFAULT_WIDTH = '500px';
   encapsulation: ViewEncapsulation.None,
 })
 export class GoogleMap implements OnChanges, OnInit, OnDestroy {
+  private _eventManager = new MapEventManager();
+
+  /** Whether we're currently rendering inside a browser. */
+  private _isBrowser: boolean;
+  private _googleMapChanges: Observable<google.maps.Map>;
+
+  private readonly _options = new BehaviorSubject<google.maps.MapOptions>(DEFAULT_OPTIONS);
+  private readonly _center =
+      new BehaviorSubject<google.maps.LatLngLiteral|google.maps.LatLng|undefined>(undefined);
+  private readonly _zoom = new BehaviorSubject<number|undefined>(undefined);
+  private readonly _destroy = new Subject<void>();
+  private _mapEl: HTMLElement;
+  _googleMap: UpdatedGoogleMap;
+
   @Input() height = DEFAULT_HEIGHT;
 
   @Input() width = DEFAULT_WIDTH;
@@ -85,125 +99,127 @@ export class GoogleMap implements OnChanges, OnInit, OnDestroy {
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.bounds_changed
    */
-  @Output() boundsChanged = new EventEmitter<void>();
+  @Output()
+  boundsChanged: Observable<void> = this._eventManager.getLazyEmitter<void>('bounds_changed');
 
   /**
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.center_changed
    */
-  @Output() centerChanged = new EventEmitter<void>();
+  @Output()
+  centerChanged: Observable<void> = this._eventManager.getLazyEmitter<void>('center_changed');
 
   /**
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.click
    */
-  @Output() mapClick = new EventEmitter<google.maps.MouseEvent|google.maps.IconMouseEvent>();
+  @Output()
+  mapClick: Observable<google.maps.MouseEvent|google.maps.IconMouseEvent> =
+      this._eventManager.getLazyEmitter<google.maps.MouseEvent|google.maps.IconMouseEvent>('click');
 
   /**
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.dblclick
    */
-  @Output() mapDblclick = new EventEmitter<google.maps.MouseEvent>();
+  @Output()
+  mapDblclick: Observable<google.maps.MouseEvent> =
+      this._eventManager.getLazyEmitter<google.maps.MouseEvent>('dblclick');
 
   /**
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.drag
    */
-  @Output() mapDrag = new EventEmitter<void>();
+  @Output() mapDrag: Observable<void> = this._eventManager.getLazyEmitter<void>('drag');
 
   /**
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.dragend
    */
-  @Output() mapDragend = new EventEmitter<void>();
+  @Output() mapDragend: Observable<void> = this._eventManager.getLazyEmitter<void>('dragend');
 
   /**
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.dragstart
    */
-  @Output() mapDragstart = new EventEmitter<void>();
+  @Output() mapDragstart: Observable<void> = this._eventManager.getLazyEmitter<void>('dragstart');
 
   /**
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.heading_changed
    */
-  @Output() headingChanged = new EventEmitter<void>();
+  @Output()
+  headingChanged: Observable<void> = this._eventManager.getLazyEmitter<void>('heading_changed');
 
   /**
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.idle
    */
-  @Output() idle = new EventEmitter<void>();
+  @Output() idle: Observable<void> = this._eventManager.getLazyEmitter<void>('idle');
 
   /**
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.maptypeid_changed
    */
-  @Output() maptypeidChanged = new EventEmitter<void>();
+  @Output()
+  maptypeidChanged: Observable<void> = this._eventManager.getLazyEmitter<void>('maptypeid_changed');
 
   /**
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.mousemove
    */
-  @Output() mapMousemove = new EventEmitter<google.maps.MouseEvent>();
+  @Output()
+  mapMousemove: Observable<google.maps.MouseEvent> =
+      this._eventManager.getLazyEmitter<google.maps.MouseEvent>('mousemove');
 
   /**
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.mouseout
    */
-  @Output() mapMouseout = new EventEmitter<google.maps.MouseEvent>();
+  @Output()
+  mapMouseout: Observable<google.maps.MouseEvent> =
+      this._eventManager.getLazyEmitter<google.maps.MouseEvent>('mouseout');
 
   /**
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.mouseover
    */
-  @Output() mapMouseover = new EventEmitter<google.maps.MouseEvent>();
+  @Output()
+  mapMouseover: Observable<google.maps.MouseEvent> =
+      this._eventManager.getLazyEmitter<google.maps.MouseEvent>('mouseover');
 
   /**
    * See
    * developers.google.com/maps/documentation/javascript/reference/map#Map.projection_changed
    */
-  @Output() projectionChanged = new EventEmitter<void>();
+  @Output()
+  projectionChanged: Observable<void> =
+      this._eventManager.getLazyEmitter<void>('projection_changed');
 
   /**
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.rightclick
    */
-  @Output() mapRightclick = new EventEmitter<google.maps.MouseEvent>();
+  @Output()
+  mapRightclick: Observable<google.maps.MouseEvent> =
+      this._eventManager.getLazyEmitter<google.maps.MouseEvent>('rightclick');
 
   /**
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.tilesloaded
    */
-  @Output() tilesloaded = new EventEmitter<void>();
+  @Output() tilesloaded: Observable<void> = this._eventManager.getLazyEmitter<void>('tilesloaded');
 
   /**
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.tilt_changed
    */
-  @Output() tiltChanged = new EventEmitter<void>();
+  @Output() tiltChanged: Observable<void> = this._eventManager.getLazyEmitter<void>('tilt_changed');
 
   /**
    * See
    * https://developers.google.com/maps/documentation/javascript/reference/map#Map.zoom_changed
    */
-  @Output() zoomChanged = new EventEmitter<void>();
-
-  private _mapEl: HTMLElement;
-  _googleMap: UpdatedGoogleMap;
-
-  /** Whether we're currently rendering inside a browser. */
-  private _isBrowser: boolean;
-  private _googleMapChanges!: Observable<google.maps.Map>;
-
-  private _listeners: google.maps.MapsEventListener[] = [];
-
-  private readonly _options = new BehaviorSubject<google.maps.MapOptions>(DEFAULT_OPTIONS);
-  private readonly _center =
-      new BehaviorSubject<google.maps.LatLngLiteral|google.maps.LatLng|undefined>(undefined);
-  private readonly _zoom = new BehaviorSubject<number|undefined>(undefined);
-
-  private readonly _destroy = new Subject<void>();
+  @Output() zoomChanged: Observable<void> = this._eventManager.getLazyEmitter<void>('zoomChanged');
 
   constructor(
     private readonly _elementRef: ElementRef,
@@ -238,13 +254,10 @@ export class GoogleMap implements OnChanges, OnInit, OnDestroy {
     if (this._isBrowser) {
       this._mapEl = this._elementRef.nativeElement.querySelector('.map-container')!;
       this._setSize();
-
-      const combinedOptionsChanges = this._combineOptions();
-
-      this._googleMapChanges = this._initializeMap(combinedOptionsChanges);
+      this._googleMapChanges = this._initializeMap(this._combineOptions());
       this._googleMapChanges.subscribe((googleMap: google.maps.Map) => {
         this._googleMap = googleMap as UpdatedGoogleMap;
-        this._initializeEventHandlers(this._googleMap);
+        this._eventManager.setTarget(this._googleMap);
       });
 
       this._watchForOptionsChanges();
@@ -254,9 +267,9 @@ export class GoogleMap implements OnChanges, OnInit, OnDestroy {
   }
 
   ngOnDestroy() {
+    this._eventManager.destroy();
     this._destroy.next();
     this._destroy.complete();
-    this._clearListeners();
   }
 
   /**
@@ -472,64 +485,7 @@ export class GoogleMap implements OnChanges, OnInit, OnDestroy {
         });
   }
 
-  private _initializeEventHandlers(googleMap: UpdatedGoogleMap) {
-    // Ensure that we don't leak if called multiple times.
-    this._clearListeners();
-
-    const eventHandlers = new Map<string, EventEmitter<void>>([
-      ['bounds_changed', this.boundsChanged],
-      ['center_changed', this.centerChanged],
-      ['drag', this.mapDrag],
-      ['dragend', this.mapDragend],
-      ['dragstart', this.mapDragstart],
-      ['heading_changed', this.headingChanged],
-      ['idle', this.idle],
-      ['maptypeid_changed', this.maptypeidChanged],
-      ['projection_changed', this.projectionChanged],
-      ['tilesloaded', this.tilesloaded],
-      ['tilt_changed', this.tiltChanged],
-      ['zoomChanged', this.zoomChanged],
-    ]);
-    const mouseEventHandlers = new Map<string, EventEmitter<google.maps.MouseEvent>>([
-      ['dblclick', this.mapDblclick],
-      ['mousemove', this.mapMousemove],
-      ['mouseout', this.mapMouseout],
-      ['mouseover', this.mapMouseover],
-      ['rightclick', this.mapRightclick],
-    ]);
-    eventHandlers.forEach((eventHandler: EventEmitter<void>, name: string) => {
-      if (eventHandler.observers.length > 0) {
-        this._listeners.push(googleMap.addListener(name, () => {
-          eventHandler.emit();
-        }));
-      }
-    });
-    mouseEventHandlers.forEach(
-        (eventHandler: EventEmitter<google.maps.MouseEvent>, name: string) => {
-          if (eventHandler.observers.length > 0) {
-            this._listeners.push(
-                googleMap.addListener(name, (event: google.maps.MouseEvent) => {
-                  eventHandler.emit(event);
-                }));
-          }
-        });
-    if (this.mapClick.observers.length > 0) {
-      this._listeners.push(googleMap.addListener(
-          'click', (event: google.maps.MouseEvent|google.maps.IconMouseEvent) => {
-            this.mapClick.emit(event);
-          }));
-    }
-  }
-
-  /** Clears all currently-registered event listeners. */
-  private _clearListeners() {
-    for (let listener of this._listeners) {
-      listener.remove();
-    }
-
-    this._listeners = [];
-  }
-
+  /** Asserts that the map has been initialized. */
   private _assertInitialized() {
     if (!this._googleMap) {
       throw Error('Cannot access Google Map information before the API has been initialized. ' +