From 7edb026619eb0ae78559065e7c10b7acfedc1f82 Mon Sep 17 00:00:00 2001
From: Lars Gyrup Brink Nielsen <larsbrinknielsen@gmail.com>
Date: Fri, 5 Jun 2020 23:24:35 +0200
Subject: [PATCH] fix(common): prevent duplicate URL change notifications
 (#37459)

Prevent duplicate notifications from being emitted when multiple URL change listeners are registered using SpyLocation#onUrlChange.

Use `@internal` annotation for the `_urlChangeSubscription` properties instead of the `private` access modifier. Otherwise, we get in trouble because of  `SpyLocation implements Location`.

PR Close #37459
---
 packages/common/src/location/location.ts     |  3 ++-
 packages/common/testing/src/location_mock.ts | 11 ++++++++---
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/packages/common/src/location/location.ts b/packages/common/src/location/location.ts
index fbf0675cc8..55af1e738d 100644
--- a/packages/common/src/location/location.ts
+++ b/packages/common/src/location/location.ts
@@ -64,7 +64,8 @@ export class Location {
   _platformLocation: PlatformLocation;
   /** @internal */
   _urlChangeListeners: ((url: string, state: unknown) => void)[] = [];
-  private _urlChangeSubscription?: SubscriptionLike;
+  /** @internal */
+  _urlChangeSubscription?: SubscriptionLike;
 
   constructor(platformStrategy: LocationStrategy, platformLocation: PlatformLocation) {
     this._platformStrategy = platformStrategy;
diff --git a/packages/common/testing/src/location_mock.ts b/packages/common/testing/src/location_mock.ts
index 28f57c26a5..e7f5595ec9 100644
--- a/packages/common/testing/src/location_mock.ts
+++ b/packages/common/testing/src/location_mock.ts
@@ -30,6 +30,8 @@ export class SpyLocation implements Location {
   _platformLocation: PlatformLocation = null!;
   /** @internal */
   _urlChangeListeners: ((url: string, state: unknown) => void)[] = [];
+  /** @internal */
+  _urlChangeSubscription?: SubscriptionLike;
 
   setInitialPath(url: string) {
     this._history[this._historyIndex].path = url;
@@ -123,9 +125,12 @@ export class SpyLocation implements Location {
   }
   onUrlChange(fn: (url: string, state: unknown) => void) {
     this._urlChangeListeners.push(fn);
-    this.subscribe(v => {
-      this._notifyUrlChangeListeners(v.url, v.state);
-    });
+
+    if (!this._urlChangeSubscription) {
+      this._urlChangeSubscription = this.subscribe(v => {
+        this._notifyUrlChangeListeners(v.url, v.state);
+      });
+    }
   }
 
   /** @internal */