fix: client owned NetworkObject with prefabhandler destroy order incorrect on host-server side (Backport)

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -12,6 +12,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 
 ### Fixed
 
+- Fixed issue where a spawned `NetworkObject` that was registered with a prefab handler and owned by a client would invoke destroy more than once on the host-server side if the client disconnected while the `NetworkObject` was still spawned. (#3202)
 - Fixed issue where `NetworkRigidBody2D` was still using the deprecated `isKinematic` property in Unity versions 2022.3 and newer. (#3199)
 - Fixed issue where an exception was thrown when calling `NetworkManager.Shutdown` after calling `UnityTransport.Shutdown`. (#3118)
 

com.unity.netcode.gameobjects/Runtime/Connection/NetworkConnectionManager.cs

@@ -967,6 +967,11 @@ internal void OnClientDisconnectFromServer(ulong clientId)
                     {
                         if (NetworkManager.PrefabHandler.ContainsHandler(ConnectedClients[clientId].PlayerObject.GlobalObjectIdHash))
                         {
+                            // If the player is spawned, then despawn before invoking HandleNetworkPrefabDestroy
+                            if (playerObject.IsSpawned)
+                            {
+                                NetworkManager.SpawnManager.DespawnObject(ConnectedClients[clientId].PlayerObject, false);
+                            }
                             NetworkManager.PrefabHandler.HandleNetworkPrefabDestroy(ConnectedClients[clientId].PlayerObject);
                         }
                         else if (playerObject.IsSpawned)
@@ -984,40 +989,34 @@ internal void OnClientDisconnectFromServer(ulong clientId)
 
                 // Get the NetworkObjects owned by the disconnected client
                 var clientOwnedObjects = NetworkManager.SpawnManager.GetClientOwnedObjects(clientId);
-                if (clientOwnedObjects == null)
+
+                // Handle despawn & destroy or change ownership
+                for (int i = clientOwnedObjects.Count - 1; i >= 0; i--)
                 {
-                    // This could happen if a client is never assigned a player object and is disconnected
-                    // Only log this in verbose/developer mode
-                    if (NetworkManager.LogLevel == LogLevel.Developer)
+                    var ownedObject = clientOwnedObjects[i];
+                    if (!ownedObject)
                     {
-                        NetworkLog.LogWarning($"ClientID {clientId} disconnected with (0) zero owned objects!  Was a player prefab not assigned?");
+                        continue;
                     }
-                }
-                else
-                {
-                    // Handle changing ownership and prefab handlers
-                    for (int i = clientOwnedObjects.Count - 1; i >= 0; i--)
+                    if (!ownedObject.DontDestroyWithOwner)
                     {
-                        var ownedObject = clientOwnedObjects[i];
-                        if (ownedObject != null)
+                        if (NetworkManager.PrefabHandler.ContainsHandler(clientOwnedObjects[i].GlobalObjectIdHash))
                         {
-                            if (!ownedObject.DontDestroyWithOwner)
+                            if (ownedObject.IsSpawned)
                             {
-                                if (NetworkManager.PrefabHandler.ContainsHandler(clientOwnedObjects[i].GlobalObjectIdHash))
-                                {
-                                    NetworkManager.PrefabHandler.HandleNetworkPrefabDestroy(clientOwnedObjects[i]);
-                                }
-                                else
-                                {
-                                    Object.Destroy(ownedObject.gameObject);
-                                }
-                            }
-                            else if (!NetworkManager.ShutdownInProgress)
-                            {
-                                ownedObject.RemoveOwnership();
+                                NetworkManager.SpawnManager.DespawnObject(ownedObject, false);
                             }
+                            NetworkManager.PrefabHandler.HandleNetworkPrefabDestroy(clientOwnedObjects[i]);
+                        }
+                        else
+                        {
+                            Object.Destroy(ownedObject.gameObject);
                         }
                     }
+                    else if (!NetworkManager.ShutdownInProgress)
+                    {
+                        ownedObject.RemoveOwnership();
+                    }
                 }
 
                 // TODO: Could(should?) be replaced with more memory per client, by storing the visibility

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

@@ -435,10 +435,15 @@ internal NetworkObject InstantiateAndSpawnNoParameterChecks(NetworkObject networ
 
             var networkObject = networkPrefab;
             // Host spawns the ovveride and server spawns the original prefab unless forceOverride is set to true where both server or host will spawn the override.
-            if (forceOverride || NetworkManager.IsHost)
+            if (forceOverride || NetworkManager.IsHost || NetworkManager.PrefabHandler.ContainsHandler(networkPrefab.GlobalObjectIdHash))
             {
                 networkObject = GetNetworkObjectToSpawn(networkPrefab.GlobalObjectIdHash, ownerClientId, position, rotation);
             }
+            else // Under this case, server instantiate the prefab passed in.
+            {
+                networkObject = InstantiateNetworkPrefab(networkPrefab.gameObject, networkPrefab.GlobalObjectIdHash, position, rotation);
+            }
+
             if (networkObject == null)
             {
                 Debug.LogError($"Failed to instantiate and spawn {networkPrefab.name}!");
@@ -447,7 +452,15 @@ internal NetworkObject InstantiateAndSpawnNoParameterChecks(NetworkObject networ
             networkObject.IsPlayerObject = isPlayerObject;
             networkObject.transform.position = position;
             networkObject.transform.rotation = rotation;
-            networkObject.SpawnWithOwnership(ownerClientId, destroyWithScene);
+            // If spawning as a player, then invoke SpawnAsPlayerObject
+            if (isPlayerObject)
+            {
+                networkObject.SpawnAsPlayerObject(ownerClientId, destroyWithScene);
+            }
+            else // Otherwise just spawn with ownership
+            {
+                networkObject.SpawnWithOwnership(ownerClientId, destroyWithScene);
+            }
             return networkObject;
         }
 
@@ -512,17 +525,38 @@ internal NetworkObject GetNetworkObjectToSpawn(uint globalObjectIdHash, ulong ow
                 }
                 else
                 {
-                    // Create prefab instance
-                    networkObject = UnityEngine.Object.Instantiate(networkPrefabReference).GetComponent<NetworkObject>();
-                    networkObject.transform.position = position ?? networkObject.transform.position;
-                    networkObject.transform.rotation = rotation ?? networkObject.transform.rotation;
-                    networkObject.NetworkManagerOwner = NetworkManager;
-                    networkObject.PrefabGlobalObjectIdHash = globalObjectIdHash;
+                    // Create prefab instance while applying any pre-assigned position and rotation values
+                    networkObject = InstantiateNetworkPrefab(networkPrefabReference, globalObjectIdHash, position, rotation);
                 }
             }
             return networkObject;
         }
 
+        /// <summary>
+        /// Instantiates a network prefab instance, assigns the base prefab <see cref="NetworkObject.GlobalObjectIdHash"/>, positions, and orients
+        /// the instance.
+        /// !!! Should only be invoked by <see cref="GetNetworkObjectToSpawn"/> unless used by an integration test !!!
+        /// </summary>
+        /// <remarks>
+        /// <param name="prefabGlobalObjectIdHash"> should be the base prefab <see cref="NetworkObject.GlobalObjectIdHash"/> value and not the
+        /// overrided value.
+        /// (Can be used for integration testing)
+        /// </remarks>
+        /// <param name="networkPrefab">prefab to instantiate</param>
+        /// <param name="prefabGlobalObjectIdHash"><see cref="NetworkObject.GlobalObjectIdHash"/> of the base prefab instance</param>
+        /// <param name="position">conditional position in place of the network prefab's default position</param>
+        /// <param name="rotation">conditional rotation in place of the network prefab's default rotation</param>
+        /// <returns>the instance of the <see cref="NetworkObject"/></returns>
+        internal NetworkObject InstantiateNetworkPrefab(GameObject networkPrefab, uint prefabGlobalObjectIdHash, Vector3? position, Quaternion? rotation)
+        {
+            var networkObject = UnityEngine.Object.Instantiate(networkPrefab).GetComponent<NetworkObject>();
+            networkObject.transform.position = position ?? networkObject.transform.position;
+            networkObject.transform.rotation = rotation ?? networkObject.transform.rotation;
+            networkObject.NetworkManagerOwner = NetworkManager;
+            networkObject.PrefabGlobalObjectIdHash = prefabGlobalObjectIdHash;
+            return networkObject;
+        }
+
         /// <summary>
         /// Creates a local NetowrkObject to be spawned.
         /// </summary>

com.unity.netcode.gameobjects/TestHelpers/Runtime/NetcodeIntegrationTestHelpers.cs

@@ -527,6 +527,29 @@ public static void MakeNetworkObjectTestPrefab(NetworkObject networkObject, uint
             }
         }
 
+        /// <summary>
+        /// Creates a <see cref="NetworkObject"/> to be used with integration testing
+        /// </summary>
+        /// <param name="baseName">namr of the object</param>
+        /// <param name="owner">owner of the object</param>
+        /// <param name="moveToDDOL">when true, the instance is automatically migrated into the DDOL</param>
+        /// <returns></returns>
+        internal static GameObject CreateNetworkObject(string baseName, NetworkManager owner, bool moveToDDOL = false)
+        {
+            var gameObject = new GameObject
+            {
+                name = baseName
+            };
+            var networkObject = gameObject.AddComponent<NetworkObject>();
+            networkObject.NetworkManagerOwner = owner;
+            MakeNetworkObjectTestPrefab(networkObject);
+            if (moveToDDOL)
+            {
+                Object.DontDestroyOnLoad(gameObject);
+            }
+            return gameObject;
+        }
+
         public static GameObject CreateNetworkObjectPrefab(string baseName, NetworkManager server, params NetworkManager[] clients)
         {
             void AddNetworkPrefab(NetworkConfig config, NetworkPrefab prefab)
@@ -538,13 +561,7 @@ void AddNetworkPrefab(NetworkConfig config, NetworkPrefab prefab)
             Assert.IsNotNull(server, prefabCreateAssertError);
             Assert.IsFalse(server.IsListening, prefabCreateAssertError);
 
-            var gameObject = new GameObject
-            {
-                name = baseName
-            };
-            var networkObject = gameObject.AddComponent<NetworkObject>();
-            networkObject.NetworkManagerOwner = server;
-            MakeNetworkObjectTestPrefab(networkObject);
+            var gameObject = CreateNetworkObject(baseName, server);
             var networkPrefab = new NetworkPrefab() { Prefab = gameObject };
 
             // We could refactor this test framework to share a NetworkPrefabList instance, but at this point it's