Messaging token refresh delegate should be able to return null token (#6647)

Author: charlotteliang

FirebaseMessaging/Apps/Sample/Sample/SceneDelegate.swift

@@ -72,7 +72,7 @@ class SceneDelegate: UIResponder, UIWindowSceneDelegate, MessagingDelegate {
       .store(in: &cancellables)
   }
 
-  func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String) {
+  func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String?) {
     identity.token = fcmToken
   }
 }

FirebaseMessaging/CHANGELOG.md

@@ -1,5 +1,6 @@
 # unreleased -- v.7.0.0
 - [changed] Remove the deprecated FCM direct channel API and Upstream send API. (#6430)
+- [changed] The `messaging:didReceiveRegistrationToken:` should be able to return a null token. Update the API parameter fcmToken to be nullable. (#5339)
 - [fixed] Fixed an issue that downloading an image failed when there's no extension in the file name but MIME type is set. (#6590)
 
 # 2020-09 -- v.4.7.1

FirebaseMessaging/Sources/Public/FirebaseMessaging/FIRMessaging.h

@@ -146,7 +146,7 @@ NS_SWIFT_NAME(MessagingDelegate)
 ///
 /// * Subscribing to any topics.
 - (void)messaging:(FIRMessaging *)messaging
-    didReceiveRegistrationToken:(NSString *)fcmToken
+    didReceiveRegistrationToken:(nullable NSString *)fcmToken
     NS_SWIFT_NAME(messaging(_:didReceiveRegistrationToken:));
 @end
 

FirebaseMessaging/Tests/IntegrationTests/FIRMessagingTokenRefreshTests.swift

@@ -28,7 +28,7 @@
     var messaging = Messaging.messaging()
     var delegateIsCalled = false
 
-    func messaging(_: Messaging, didReceiveRegistrationToken _: String) {
+    func messaging(_: Messaging, didReceiveRegistrationToken _: String?) {
       delegateIsCalled = true
     }
   }