fix: catching potential exceptions from user code during disconnect callback (#2288)

* fix: catching potential exceptions from user code during disconnect callback

Author: jeffreyrainy

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

@@ -1831,7 +1831,14 @@ private void HandleRawTransportPoll(NetworkEvent networkEvent, ulong clientId, A
                     // or, if we are the server, so we got everything from that client.
                     MessagingSystem.ProcessIncomingMessageQueue();
 
-                    OnClientDisconnectCallback?.Invoke(clientId);
+                    try
+                    {
+                        OnClientDisconnectCallback?.Invoke(clientId);
+                    }
+                    catch (Exception exception)
+                    {
+                        Debug.LogException(exception);
+                    }
 
                     if (IsServer)
                     {

com.unity.netcode.gameobjects/Tests/Runtime/DisconnectReasonTests.cs

@@ -0,0 +1,60 @@
+using System;
+using System.Collections;
+using System.Text.RegularExpressions;
+using UnityEngine;
+using UnityEngine.TestTools;
+using Unity.Netcode.TestHelpers.Runtime;
+
+namespace Unity.Netcode.RuntimeTests
+{
+    public class DisconnectReasonObject : NetworkBehaviour
+    {
+
+    }
+
+    public class DisconnectReasonTests : NetcodeIntegrationTest
+    {
+        protected override int NumberOfClients => 2;
+
+        private GameObject m_PrefabToSpawn;
+
+        protected override void OnServerAndClientsCreated()
+        {
+            m_PrefabToSpawn = CreateNetworkObjectPrefab("DisconnectReasonObject");
+            m_PrefabToSpawn.AddComponent<DisconnectReasonObject>();
+        }
+
+        private int m_DisconnectCount;
+
+        public void OnClientDisconnectCallback(ulong clientId)
+        {
+            m_DisconnectCount++;
+            throw new SystemException("whatever");
+        }
+
+        [UnityTest]
+        public IEnumerator DisconnectExceptionTest()
+        {
+            float startTime = Time.realtimeSinceStartup;
+
+            // Add a callback for first client, when they get disconnected
+            m_ClientNetworkManagers[0].OnClientDisconnectCallback += OnClientDisconnectCallback;
+            m_ClientNetworkManagers[1].OnClientDisconnectCallback += OnClientDisconnectCallback;
+
+            // Disconnect first client, from the server
+            LogAssert.Expect(LogType.Exception, new Regex(".*whatever.*"));
+            m_ServerNetworkManager.DisconnectClient(m_ClientNetworkManagers[0].LocalClientId);
+
+            // Disconnect second client, from the server
+            LogAssert.Expect(LogType.Exception, new Regex(".*whatever.*"));
+            m_ServerNetworkManager.DisconnectClient(m_ClientNetworkManagers[1].LocalClientId);
+
+            while (m_DisconnectCount < 2 && Time.realtimeSinceStartup < startTime + 10.0f)
+            {
+                yield return null;
+            }
+
+            Debug.Assert(m_DisconnectCount == 2);
+        }
+    }
+}