- Ensure NetworkManager.Singleton is always the server when there are multiple NetworkManagers

- Ensure UnifiedBootstrap doesn't get replaced when setting up a new NetworkManager, as that clears out the list of network worlds.

Author: ShadauxCat

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

@@ -1092,7 +1092,10 @@ internal static void ResetSingleton()
         /// </summary>
         public void SetSingleton()
         {
-            Singleton = this;
+            if (!Singleton || !Singleton.IsServer)
+            {
+                Singleton = this;
+            }
 
             OnSingletonReady?.Invoke();
         }
@@ -1401,7 +1404,14 @@ internal void InitializeNetcodeWorld()
             /// !! Initialize worlds here !!
             /// Worlds are created here: <see cref="UnifiedBootStrap.Initialize"/>
             UnifiedBootstrap.CurrentNetworkManagerForInitialization = this;
-            DefaultWorldInitialization.Initialize("Default World", false);
+            if (UnifiedBootstrap.Instance != null)
+            {
+                UnifiedBootstrap.Instance.Initialize("Default World");
+            }
+            else
+            {
+                DefaultWorldInitialization.Initialize("Default World", false);
+            }
         }
 
         /// <summary>

com.unity.netcode.gameobjects/Runtime/Spawning/NetworkSpawnManager.cs

@@ -939,14 +939,6 @@ internal NetworkObject GetNetworkObjectToSpawn(uint globalObjectIdHash, ulong ow
         /// <returns>the instance of the <see cref="NetworkObject"/></returns>
         internal NetworkObject InstantiateNetworkPrefab([NotNull] GameObject networkPrefab, uint prefabGlobalObjectIdHash, Vector3? position, Quaternion? rotation)
         {
-#if UNIFIED_NETCODE
-            // TODO-FixMe: NetCode.Netcode.Instance is a singleton and might cause issues
-            // assigning this.
-            if (networkPrefab.GetComponent<NetworkObject>().HasGhost)
-            {
-                NetCode.Netcode.Instance.m_ActiveWorld = NetworkManager.NetcodeWorld;
-            }
-#endif
             var gameObject = Object.Instantiate(networkPrefab);
             var networkObject = gameObject.GetComponent<NetworkObject>();
             if (networkObject == null)

com.unity.netcode.gameobjects/Tests/Runtime/TestHelpers/NetcodeIntegrationTest.cs

@@ -2449,14 +2449,6 @@ internal void SpawnInstanceWithOwnership(NetworkObject networkObjectToSpawn, Net
             }
             else
             {
-#if UNIFIED_NETCODE
-                // TODO-FixMe: NetCode.Netcode.Instance is a singleton and might cause issues
-                // assigning this.
-                if (networkObjectToSpawn.HasGhost)
-                {
-                    NetCode.Netcode.Instance.m_ActiveWorld = m_ServerNetworkManager.NetcodeWorld;
-                }
-#endif
                 networkObjectToSpawn.NetworkManagerOwner = m_ServerNetworkManager; // Required to assure the server does the spawning
                 if (spawnAuthority == m_ServerNetworkManager)
                 {
@@ -2513,14 +2505,6 @@ protected void SpawnObjectInstance(NetworkObject networkObjectToSpawn, NetworkMa
         /// <returns>GameObject instance spawned</returns>
         private GameObject SpawnObject(NetworkObject prefabNetworkObject, NetworkManager owner, bool destroyWithScene = false, bool isPlayerObject = false)
         {
-#if UNIFIED_NETCODE
-            // TODO-FixMe: NetCode.Netcode.Instance is a singleton and might cause issues
-            // assigning this.
-            if (prefabNetworkObject.HasGhost)
-            {
-                NetCode.Netcode.Instance.m_ActiveWorld = owner.NetcodeWorld;
-            }
-#endif
             Assert.IsTrue(prefabNetworkObject.GlobalObjectIdHash > 0, $"{nameof(GameObject)} {prefabNetworkObject.name} has a {nameof(NetworkObject.GlobalObjectIdHash)} value of 0! Make sure to make it a valid prefab before trying to spawn!");
             var newInstance = Object.Instantiate(prefabNetworkObject.gameObject);
             var networkObjectToSpawn = newInstance.GetComponent<NetworkObject>();

testproject/Assets/Tests/Runtime/Support/NetworkObjectSpawnerForTests.cs

@@ -78,14 +78,6 @@ private void SpawnRpc(RpcParams rpcParams = default)
 
         private void Spawn(ulong ownerId)
         {
-#if UNIFIED_NETCODE
-            // TODO-FixMe: NetCode.Netcode.Instance is a singleton and might cause issues
-            // assigning this.
-            if (ObjectToSpawn.GetComponent<NetworkObject>().HasGhost)
-            {
-                Netcode.Instance.m_ActiveWorld = NetworkManager.NetcodeWorld;
-            }
-#endif
             var instance = Instantiate(ObjectToSpawn);
             var networkObject = instance.GetComponent<NetworkObject>();
             networkObject.SpawnWithOwnership(ownerId);