fix(auth, web): unsubscribe from stream handlers after "hot restart" (#12908)

Author: russellwheatley

packages/firebase_auth/firebase_auth_web/lib/src/interop/auth.dart

@@ -8,7 +8,9 @@
 
 import 'dart:async';
 import 'dart:js_interop';
-
+import 'dart:js_interop_unsafe';
+import 'package:flutter/foundation.dart';
+import 'package:web/web.dart' as web;
 import 'package:firebase_auth_platform_interface/firebase_auth_platform_interface.dart';
 import 'package:firebase_core_web/firebase_core_web_interop.dart';
 import 'package:http_parser/http_parser.dart';
@@ -382,8 +384,7 @@ class Auth extends JsObjectWrapper<auth_interop.AuthJsImpl> {
         jsObject.onAuthStateChanged(nextWrapper.toJS, errorWrapper.toJS);
 
     await completer.future;
-
-    await (unsubscribe.callAsFunction() as JSPromise<JSAny?>?)?.toDart;
+    unsubscribe.callAsFunction();
   }
 
   JSFunction? _onAuthUnsubscribe;
@@ -394,13 +395,42 @@ class Auth extends JsObjectWrapper<auth_interop.AuthJsImpl> {
   // ignore: close_sinks
   StreamController<User?>? _changeController;
 
+  String get authStateWindowsKey => 'flutterfire-${app.name}_authStateChanges';
+  String get idTokenStateWindowsKey => 'flutterfire-${app.name}_idTokenChanges';
+
+  // No way to unsubscribe from event listeners on hot reload so we set on the windows object
+  // and clean up on hot restart if it exists.
+  // See: https://github.com/firebase/flutterfire/issues/7064
+  void _unsubscribeWindowsListener(String key) {
+    if (kDebugMode) {
+      final unsubscribe = web.window.getProperty(key.toJS);
+      if (unsubscribe != null) {
+        (unsubscribe as JSFunction).callAsFunction();
+      }
+    }
+  }
+
+  void _setWindowsListener(String key, JSFunction unsubscribe) {
+    if (kDebugMode) {
+      web.window.setProperty(key.toJS, unsubscribe);
+    }
+  }
+
+  void _removeWindowsListener(String key) {
+    if (kDebugMode) {
+      web.window.delete(key.toJS);
+    }
+  }
+
   /// Sends events when the users sign-in state changes.
   ///
   /// After 4.0.0, this is only triggered on sign-in or sign-out.
   /// To keep the old behavior, see [onIdTokenChanged].
   ///
   /// If the value is `null`, there is no signed-in user.
   Stream<User?> get onAuthStateChanged {
+    _unsubscribeWindowsListener(authStateWindowsKey);
+
     if (_changeController == null) {
       final nextWrapper = (auth_interop.UserJsImpl? user) {
         _changeController!.add(User.getInstance(user));
@@ -410,15 +440,17 @@ class Auth extends JsObjectWrapper<auth_interop.AuthJsImpl> {
 
       void startListen() {
         assert(_onAuthUnsubscribe == null);
-        _onAuthUnsubscribe =
+        final unsubscribe =
             jsObject.onAuthStateChanged(nextWrapper.toJS, errorWrapper.toJS);
+        _onAuthUnsubscribe = unsubscribe;
+        _setWindowsListener(authStateWindowsKey, unsubscribe);
       }
 
-      Future<void> stopListen() async {
-        await (_onAuthUnsubscribe!.callAsFunction() as JSPromise<JSAny?>?)
-            ?.toDart;
+      void stopListen() {
+        _onAuthUnsubscribe!.callAsFunction();
         _onAuthUnsubscribe = null;
         _changeController = null;
+        _removeWindowsListener(authStateWindowsKey);
       }
 
       _changeController = StreamController<User?>.broadcast(
@@ -444,6 +476,7 @@ class Auth extends JsObjectWrapper<auth_interop.AuthJsImpl> {
   ///
   /// If the value is `null`, there is no signed-in user.
   Stream<User?> get onIdTokenChanged {
+    _unsubscribeWindowsListener(idTokenStateWindowsKey);
     if (_idTokenChangedController == null) {
       final nextWrapper = (auth_interop.UserJsImpl? user) {
         _idTokenChangedController!.add(User.getInstance(user));
@@ -453,16 +486,17 @@ class Auth extends JsObjectWrapper<auth_interop.AuthJsImpl> {
 
       void startListen() {
         assert(_onIdTokenChangedUnsubscribe == null);
-        _onIdTokenChangedUnsubscribe =
+        final unsubscribe =
             jsObject.onIdTokenChanged(nextWrapper.toJS, errorWrapper.toJS);
+        _onIdTokenChangedUnsubscribe = unsubscribe;
+        _setWindowsListener(idTokenStateWindowsKey, unsubscribe);
       }
 
-      Future<void> stopListen() async {
-        await (_onIdTokenChangedUnsubscribe!.callAsFunction()
-                as JSPromise<JSAny?>?)
-            ?.toDart;
+      void stopListen() {
+        _onIdTokenChangedUnsubscribe!.callAsFunction();
         _onIdTokenChangedUnsubscribe = null;
         _idTokenChangedController = null;
+        _removeWindowsListener(idTokenStateWindowsKey);
       }
 
       _idTokenChangedController = StreamController<User?>.broadcast(