fix

This fixes the issue where spawning a prefab that is configured to be spawned with no observers just prior to synchronizing a client and showing the spawned object to the client about to be synchronized within a NetworkBehaviour attached to the newly spawn prefab instance would result in a duplicate creation of the same prefab instance due to NetworkShow being deferred until the end of the frame.

This fix excludes any spawned NetworkObjects that have pending visibility for a client that is being synchronized.

Author: NoelStephensUnity

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

@@ -324,6 +324,12 @@ internal void AddSpawnedNetworkObjects()
             var distributedAuthoritySendingToService = m_NetworkManager.DistributedAuthorityMode && TargetClientId == NetworkManager.ServerClientId;
             foreach (var sobj in m_NetworkManager.SpawnManager.SpawnedObjectsList)
             {
+                var spawnedObject = sobj;
+                // Don't synchronize objects that have pending visibility as that will be sent as a CreateObjectMessage towards the end of the current frame
+                if (TargetClientId != NetworkManager.ServerClientId && m_NetworkManager.SpawnManager.IsObjectVisibilityPending(TargetClientId,ref spawnedObject))
+                {
+                    continue;
+                }
                 if (sobj.Observers.Contains(TargetClientId) || distributedAuthoritySendingToService)
                 {
                     m_NetworkObjectsSync.Add(sobj);