Remove LocalStorage synchronization on storage events in Safari (#8408)

.changeset/mighty-shirts-pump.md

@@ -0,0 +1,5 @@
+---
+'@firebase/auth': patch
+---
+
+Remove localStorage synchronization on storage events in Safari iframes. See [GitHub PR #8408](https://github.com/firebase/firebase-js-sdk/pull/8408).

packages/auth/src/platform_browser/persistence/local_storage.ts

@@ -17,14 +17,7 @@
 
 import { Persistence } from '../../model/public_types';
 
-import { getUA } from '@firebase/util';
-import {
-  _isSafari,
-  _isIOS,
-  _isIframe,
-  _isMobileBrowser,
-  _isIE10
-} from '../../core/util/browser';
+import { _isMobileBrowser, _isIE10 } from '../../core/util/browser';
 import {
   PersistenceInternal as InternalPersistence,
   PersistenceType,
@@ -33,11 +26,6 @@ import {
 } from '../../core/persistence';
 import { BrowserPersistenceClass } from './browser';
 
-function _iframeCannotSyncWebStorage(): boolean {
-  const ua = getUA();
-  return _isSafari(ua) || _isIOS(ua);
-}
-
 // The polling period in case events are not supported
 export const _POLLING_INTERVAL_MS = 1000;
 
@@ -64,9 +52,6 @@ class BrowserLocalPersistence
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   private pollTimer: any | null = null;
 
-  // Safari or iOS browser and embedded in an iframe.
-  private readonly safariLocalStorageNotSynced =
-    _iframeCannotSyncWebStorage() && _isIframe();
   // Whether to use polling instead of depending on window events
   private readonly fallbackToPolling = _isMobileBrowser();
   readonly _shouldAllowMigration = true;
@@ -112,26 +97,6 @@ class BrowserLocalPersistence
       this.stopPolling();
     }
 
-    // Safari embedded iframe. Storage event will trigger with the delta
-    // changes but no changes will be applied to the iframe localStorage.
-    if (this.safariLocalStorageNotSynced) {
-      // Get current iframe page value.
-      const storedValue = this.storage.getItem(key);
-      // Value not synchronized, synchronize manually.
-      if (event.newValue !== storedValue) {
-        if (event.newValue !== null) {
-          // Value changed from current value.
-          this.storage.setItem(key, event.newValue);
-        } else {
-          // Current value deleted.
-          this.storage.removeItem(key);
-        }
-      } else if (this.localCache[key] === event.newValue && !poll) {
-        // Already detected and processed, do not trigger listeners again.
-        return;
-      }
-    }
-
     const triggerListeners = (): void => {
       // Keep local map up to date in case storage event is triggered before
       // poll.