fix: Adds a null check for NetworkObjectReference => GameObject conversion [NCCBUG-172]

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -13,6 +13,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 
 - Fixed ClientRpcs always reporting in the profiler view as going to all clients, even when limited to a subset of clients by ClientRpcParams. (#2144)
 - Fixed RPC codegen failing to choose the correct extension methods for FastBufferReader and FastBufferWriter when the parameters were a generic type (i.e., List<int>) and extensions for multiple instantiations of that type have been defined (i.e., List<int> and List<string>) (#2142)
+- Implicit conversion of NetworkObjectReference to GameObject will now return null instead of throwing an exception if the referenced object could not be found (i.e., was already despawned) (#2158)
 - Fixed throwing an exception in OnNetworkUpdate causing other OnNetworkUpdate calls to not be executed. (#1739)
 
 ## [1.0.1] - 2022-08-23

com.unity.netcode.gameobjects/Runtime/Serialization/NetworkObjectReference.cs

@@ -139,7 +139,7 @@ public void NetworkSerialize<T>(BufferSerializer<T> serializer) where T : IReade
         /// </summary>
         /// <param name="networkObjectRef">The <see cref="NetworkObjectReference"/> to convert from.</param>
         /// <returns>This returns the <see cref="GameObject"/> that the <see cref="NetworkObject"/> is attached to and is referenced by the <see cref="NetworkObjectReference"/> passed in as a parameter</returns>
-        public static implicit operator GameObject(NetworkObjectReference networkObjectRef) => Resolve(networkObjectRef).gameObject;
+        public static implicit operator GameObject(NetworkObjectReference networkObjectRef) => Resolve(networkObjectRef)?.gameObject;
 
         /// <summary>
         /// Implicitly convert <see cref="GameObject"/> to <see cref="NetworkObject"/>.

com.unity.netcode.gameobjects/Tests/Runtime/Serialization/NetworkObjectReferenceTests.cs

@@ -25,9 +25,12 @@ private class TestNetworkBehaviour : NetworkBehaviour
 
             public GameObject RpcReceivedGameObject;
 
+            public bool ReceivedRpc;
+
             [ServerRpc]
             public void SendReferenceServerRpc(NetworkObjectReference value)
             {
+                ReceivedRpc = true;
                 RpcReceivedGameObject = value;
                 RpcReceivedNetworkObject = value;
             }
@@ -110,6 +113,49 @@ public void TestSerializeGameObject()
             }
         }
 
+        [Test]
+        public void TestNoExceptionsIfObjectDisappears()
+        {
+            using var networkObjectContext = UnityObjectContext.CreateNetworkObject();
+            networkObjectContext.Object.Spawn();
+
+            var outWriter = new FastBufferWriter(1300, Allocator.Temp);
+            try
+            {
+                // serialize
+                var outSerializer = new BufferSerializer<BufferSerializerWriter>(new BufferSerializerWriter(outWriter));
+                NetworkObjectReference outReference = networkObjectContext.Object.gameObject;
+                outReference.NetworkSerialize(outSerializer);
+
+                networkObjectContext.Object.Despawn();
+                Object.DestroyImmediate(networkObjectContext.Object.gameObject);
+
+                // deserialize
+                NetworkObjectReference inReference = default;
+                var inReader = new FastBufferReader(outWriter, Allocator.Temp);
+                try
+                {
+                    var inSerializer =
+                        new BufferSerializer<BufferSerializerReader>(new BufferSerializerReader(inReader));
+                    inReference.NetworkSerialize(inSerializer);
+                }
+                finally
+                {
+                    inReader.Dispose();
+                }
+                GameObject gameObject = inReference;
+                NetworkObject networkObject = inReference;
+
+                // because the object is gone, it won't exist on the now, so it should end up null and shouldn't throw exceptions.
+                Assert.AreEqual(null, networkObject);
+                Assert.AreEqual(null, gameObject);
+            }
+            finally
+            {
+                outWriter.Dispose();
+            }
+        }
+
         [Test]
         public void TestTryGet()
         {