fix: Fixed enum networkvariables throwing exceptions (#1999)

Author: ShadauxCat

com.unity.netcode.gameobjects/Runtime/NetworkVariable/NetworkVariableSerialization.cs

@@ -207,16 +207,25 @@ private static INetworkVariableSerializer<T> GetSerializer()
             {
                 return new UnmanagedTypeSerializer<T>();
             }
+            if (typeof(Enum).IsAssignableFrom(typeof(T)))
+            {
+                return new UnmanagedTypeSerializer<T>();
+            }
 
             if (typeof(INetworkSerializable).IsAssignableFrom(typeof(T)))
             {
+                // Obtains "Open Instance Delegates" for the type's NetworkSerialize() methods -
+                // one for an instance of the generic method taking BufferSerializerWriter as T,
+                // one for an instance of the generic method taking BufferSerializerReader as T
                 var writeMethod = (NetworkSerializableSerializer<T>.WriteValueDelegate)Delegate.CreateDelegate(typeof(NetworkSerializableSerializer<T>.WriteValueDelegate), null, typeof(T).GetMethod(nameof(INetworkSerializable.NetworkSerialize)).MakeGenericMethod(typeof(BufferSerializerWriter)));
                 var readMethod = (NetworkSerializableSerializer<T>.ReadValueDelegate)Delegate.CreateDelegate(typeof(NetworkSerializableSerializer<T>.ReadValueDelegate), null, typeof(T).GetMethod(nameof(INetworkSerializable.NetworkSerialize)).MakeGenericMethod(typeof(BufferSerializerReader)));
                 return new NetworkSerializableSerializer<T> { WriteValue = writeMethod, ReadValue = readMethod };
             }
 
             if (typeof(IUTF8Bytes).IsAssignableFrom(typeof(T)) && typeof(INativeList<byte>).IsAssignableFrom(typeof(T)))
             {
+                // Get "OpenInstanceDelegates" for the Length property (get and set, which are prefixed
+                // with "get_" and "set_" under the hood and emitted as methods) and GetUnsafePtr()
                 var getLength = (FixedStringSerializer<T>.GetLengthDelegate)Delegate.CreateDelegate(typeof(FixedStringSerializer<T>.GetLengthDelegate), null, typeof(T).GetMethod("get_" + nameof(INativeList<byte>.Length)));
                 var setLength = (FixedStringSerializer<T>.SetLengthDelegate)Delegate.CreateDelegate(typeof(FixedStringSerializer<T>.SetLengthDelegate), null, typeof(T).GetMethod("set_" + nameof(INativeList<byte>.Length)));
                 var getUnsafePtr = (FixedStringSerializer<T>.GetUnsafePtrDelegate)Delegate.CreateDelegate(typeof(FixedStringSerializer<T>.GetUnsafePtrDelegate), null, typeof(T).GetMethod(nameof(IUTF8Bytes.GetUnsafePtr)));

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

@@ -271,7 +271,14 @@ public override int GetHashCode()
 
     public class NetworkVariableTest : NetworkBehaviour
     {
+        public enum SomeEnum
+        {
+            A,
+            B,
+            C
+        }
         public readonly NetworkVariable<int> TheScalar = new NetworkVariable<int>();
+        public readonly NetworkVariable<SomeEnum> TheEnum = new NetworkVariable<SomeEnum>();
         public readonly NetworkList<int> TheList = new NetworkList<int>();
         public readonly NetworkList<FixedString128Bytes> TheLargeList = new NetworkList<FixedString128Bytes>();
 
@@ -598,7 +605,7 @@ public IEnumerator TestNetworkVariableStruct([Values(true, false)] bool useHost)
             bool VerifyStructure()
             {
                 return m_Player1OnClient1.TheStruct.Value.SomeBool == m_Player1OnServer.TheStruct.Value.SomeBool &&
-                    m_Player1OnClient1.TheStruct.Value.SomeInt == m_Player1OnServer.TheStruct.Value.SomeInt;
+                       m_Player1OnClient1.TheStruct.Value.SomeInt == m_Player1OnServer.TheStruct.Value.SomeInt;
             }
 
             m_Player1OnServer.TheStruct.Value = new TestStruct() { SomeInt = k_TestUInt, SomeBool = false };
@@ -608,6 +615,23 @@ bool VerifyStructure()
             yield return WaitForConditionOrTimeOut(VerifyStructure);
         }
 
+        [UnityTest]
+        public IEnumerator TestNetworkVariableEnum([Values(true, false)] bool useHost)
+        {
+            yield return InitializeServerAndClients(useHost);
+
+            bool VerifyStructure()
+            {
+                return m_Player1OnClient1.TheEnum.Value == NetworkVariableTest.SomeEnum.C;
+            }
+
+            m_Player1OnServer.TheEnum.Value = NetworkVariableTest.SomeEnum.C;
+            m_Player1OnServer.TheEnum.SetDirty(true);
+
+            // Wait for the client-side to notify it is finished initializing and spawning.
+            yield return WaitForConditionOrTimeOut(VerifyStructure);
+        }
+
         [UnityTest]
         public IEnumerator TestINetworkSerializableCallsNetworkSerialize([Values(true, false)] bool useHost)
         {