fix

Issue where distributed authority would throw an exception during scene migration due to the fact that we would throw an exception if the 1st scene in the scene migration table didn't contain the client that has authority over the NetworkObject that migrated into a new scene. Now we count how many entries were written and if that count is zero upon parsing known loaded scenes then it throws an exception.

Reverting the exclusion of DDOL synchronization (that was a red herring).

Author: NoelStephensUnity

com.unity.netcode.gameobjects/Runtime/Core/NetworkObject.cs

@@ -3661,12 +3661,6 @@ internal void SceneChangedUpdate(Scene scene, bool notify = false)
                 return;
             }
 
-            // Don't  create notification if the scene is the DDOL.
-            if (scene == NetworkManager.SceneManager.DontDestroyOnLoadScene)
-            {
-                return;
-            }
-
             SceneOriginHandle = scene.handle;
 
             // non-authority needs to update the NetworkSceneHandle

com.unity.netcode.gameobjects/Runtime/SceneManagement/NetworkSceneManager.cs

@@ -3059,6 +3059,7 @@ internal void CheckForAndSendNetworkObjectSceneChanged()
             // Some NetworkObjects still exist, send the message
             var sceneEvent = BeginSceneEvent();
             sceneEvent.SceneEventType = SceneEventType.ObjectSceneChanged;
+            // SendSceneEventData can throw an exception. We need to wrap this and recover from the exception gracefully.
             try
             {
                 SendSceneEventData(sceneEvent.SceneEventId, NetworkManager.ConnectedClientsIds.Where(c => c != NetworkManager.LocalClientId).ToArray());

com.unity.netcode.gameobjects/Runtime/SceneManagement/SceneEventData.cs

@@ -1204,31 +1204,51 @@ private void ReadSceneEventProgressDone(FastBufferReader reader)
         private void SerializeObjectsMovedIntoNewScene(FastBufferWriter writer)
         {
             var sceneManager = m_NetworkManager.SceneManager;
-            var ownerId = m_NetworkManager.LocalClientId;
+            var networkManagerClientId = m_NetworkManager.LocalClientId;
             if (IsForwarding)
             {
-                ownerId = m_OwnerId;
+                networkManagerClientId = m_OwnerId;
             }
 
             // Write the owner identifier
-            writer.WriteValueSafe(ownerId);
+            writer.WriteValueSafe(networkManagerClientId);
 
-            // Write the number of scene handles
-            writer.WriteValueSafe(sceneManager.ObjectsMigratedIntoNewScene.Count);
+            // Create a place holder for the number of entries written.
+            // Distributed authority this could end up being just a single entry for
+            // one of several scenes loaded. As such, we need to count how many entries
+            // are actually written.
+            var countPosition = writer.Position;
+            writer.WriteValueSafe(0);
+            var entriesWritten = 0;
             foreach (var sceneHandleObjects in sceneManager.ObjectsMigratedIntoNewScene)
             {
-                if (!sceneHandleObjects.Value.ContainsKey(ownerId))
+                // Since these are separated by scene then owner, there could be scenes that have
+                // no changes.
+                if (!sceneHandleObjects.Value.ContainsKey(networkManagerClientId))
                 {
-                    throw new Exception($"Trying to send object scene migration for Client-{ownerId} but the client has no entries to send!");
+                    continue;
                 }
                 // Write the scene handle
                 writer.WriteValueSafe(sceneHandleObjects.Key);
                 // Write the number of NetworkObjectIds to expect
-                writer.WriteValueSafe(sceneHandleObjects.Value[ownerId].Count);
-                foreach (var networkObject in sceneHandleObjects.Value[ownerId])
+                writer.WriteValueSafe(sceneHandleObjects.Value[networkManagerClientId].Count);
+                foreach (var networkObject in sceneHandleObjects.Value[networkManagerClientId])
                 {
                     writer.WriteValueSafe(networkObject.NetworkObjectId);
                 }
+                entriesWritten++;
+            }
+            if (entriesWritten == 0)
+            {
+                throw new Exception($"Trying to send object scene migration for Client-{networkManagerClientId} but the client has no entries to send!");
+            }
+            else
+            {
+                // Write the number of entries written
+                var endPosition = writer.Position;
+                writer.Seek(countPosition);
+                writer.WriteValueSafe(entriesWritten);
+                writer.Seek(endPosition);
             }
         }