[Messaging] Fix subscription not completing sometimes

messaging/src/android/cpp/messaging.cc

@@ -724,6 +724,11 @@ static void InstallationsGetToken() {
 
   result.OnCompletion(
       [](const Future<std::string>& result, void* voidptr) {
+        if (g_registration_token_mutex) {
+          MutexLock lock(*g_registration_token_mutex);
+          g_registration_token_received = true;
+          HandlePendingSubscriptions();
+        }
         NotifyListenerOnTokenReceived(result.result()->c_str());
       },
       nullptr);
@@ -868,6 +873,9 @@ static const char kErrorMessageNoRegistrationToken[] =
     "Cannot update subscription when SetTokenRegistrationOnInitEnabled is set "
     "to false.";
 
+static const char kErrorMessageSubscriptionUnknown[] =
+    "Cannot update subscription for unknown reason.";
+
 Future<void> Subscribe(const char* topic) {
   FIREBASE_ASSERT_MESSAGE_RETURN(Future<void>(), internal::IsInitialized(),
                                  kMessagingNotInitializedError);
@@ -882,6 +890,11 @@ Future<void> Subscribe(const char* topic) {
                   kErrorMessageNoRegistrationToken);
   } else if (g_pending_subscriptions) {
     g_pending_subscriptions->push_back(PendingTopic(topic, handle));
+  } else {
+    // This shouldn't happen, since g_pending_subscriptions should be valid if
+    // here, but handle it to prevent abandoning the Future in case something
+    // happens.
+    api->Complete(handle, kErrorUnknown, kErrorMessageSubscriptionUnknown);
   }
   return MakeFuture(api, handle);
 }
@@ -907,6 +920,11 @@ Future<void> Unsubscribe(const char* topic) {
                   kErrorMessageNoRegistrationToken);
   } else if (g_pending_unsubscriptions) {
     g_pending_unsubscriptions->push_back(PendingTopic(topic, handle));
+  } else {
+    // This shouldn't happen, since g_pending_unsubscriptions should be valid if
+    // here, but handle it to prevent abandoning the Future in case something
+    // happens.
+    api->Complete(handle, kErrorUnknown, kErrorMessageSubscriptionUnknown);
   }
   return MakeFuture(api, handle);
 }

release_build_files/readme.md

@@ -664,6 +664,8 @@ code.
       library and to the firebase::ump namespace. The version in the
       GMA library (in firebase::gma::ump) has been deprecated and will
       be removed soon.
+    - Messaging (Android): Fix issue with the Subscribe Future not completing
+      when a cached token is available.
 
 ### 12.7.0
 -   Changes