feat(common): add ability to track all location changes (#30055)

This feature adds an `onUrlChange` to Angular's `Location` class. This is useful to track all updates coming from anywhere in the framework. Without this method, it's difficult (or impossible) to track updates run through `location.go()` or `location.replaceState()` as the browser doesn't publish events when `history.pushState()` or `.replaceState()` are run.

PR Close #30055

packages/common/testing/src/location_mock.ts

@@ -6,18 +6,23 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Location, LocationStrategy} from '@angular/common';
+import {Location, LocationStrategy, PlatformLocation} from '@angular/common';
 import {EventEmitter, Injectable} from '@angular/core';
 import {SubscriptionLike} from 'rxjs';
 
 
+const urlChangeListeners: ((url: string, state: unknown) => void)[] = [];
+function notifyUrlChangeListeners(url: string = '', state: unknown) {
+  urlChangeListeners.forEach(fn => fn(url, state));
+}
+
 /**
  * A spy for {@link Location} that allows tests to fire simulated location events.
  *
  * @publicApi
  */
 @Injectable()
-export class SpyLocation implements Location {
+export class SpyLocation extends Location {
   urlChanges: string[] = [];
   private _history: LocationState[] = [new LocationState('', '', null)];
   private _historyIndex: number = 0;
@@ -27,6 +32,8 @@ export class SpyLocation implements Location {
   _baseHref: string = '';
   /** @internal */
   _platformStrategy: LocationStrategy = null !;
+  /** @internal */
+  _platformLocation: PlatformLocation = null !;
 
   setInitialPath(url: string) { this._history[this._historyIndex].path = url; }
 
@@ -110,6 +117,10 @@ export class SpyLocation implements Location {
       this._subject.emit({'url': this.path(), 'state': this.getState(), 'pop': true});
     }
   }
+  onUrlChange(fn: (url: string, state: unknown) => void) {
+    urlChangeListeners.push(fn);
+    this.subscribe(v => { notifyUrlChangeListeners(v.url, v.state); });
+  }
 
   subscribe(
       onNext: (value: any) => void, onThrow?: ((error: any) => void)|null,