Using an Enum in a NetworkVariable<T> breaks the inspector

[JayPeet]

Description

Using an enum in a NetworkVariable breaks the inspector for that component.

Reproduce Steps

I have included a small reproduction project, but the steps to do it are short.
EnumFailRepro.zip

1. Make an enum
2. Use it in a NetworkVariable on a NetworkBehaviour
3. Add the NetworkBehaviour to a GameObject
4. Note the errors in the logs + the inspector breaking when selecting the GameObject

Actual Outcome

The inspector broke, and some exceptions were logged

Expected Outcome

The inspector renders the inspector correctly with no exceptions

Environment

• OS: Win10
• Unity Version: 2022.2.10f1
• Netcode Version: 08005ff
• Netcode Commit: 08005ff

Additional Context

Looks like the issue was introduced in [https://github.com/Unity-Technologies/com.unity.netcode.gameobjects/commit/65e176e185aeba53988c2093649a9a1f5740dae7] due to adding the constraint of IEquatable to the RenderNetworkContainerValueType function. Enums are not able to implement interfaces, and they dont implement IEquatable. Unsure of how to fix this / dont have time to fix it atm.
Might need to fix it in RenderNetworkVariable itself and have 2 different code paths, one for NetworkVariable and one for NetworkList.

Broke:

After removing IEquatable from RenderNetworkContainerValueType

[NoelStephensUnity]

Hi @JayPeet,
The error is actually happening because NetworkVariables shouldn't be used as inspector properties since the only way to initialize them with a starting value is when they are instantiated. Currently, there are really only two recommended ways to instantiate NetworkVariables prior to spawn:

• When declared (won't be helpful for your use case)
• During the Awake method (will be helpful for your use case)

Based on your script, here is the recommended way to handle this:

using UnityEngine;
using Unity.Netcode;

public class ReproBehaviour : NetworkBehaviour
{
    public enum MyEnums
    {
        A,
        B,
        C
    }

    [HideInInspector]
    public NetworkVariable<MyEnums> MyEnum;

    [SerializeField]
    private MyEnums m_MyEnumSettings;

    private void Awake()
    {
        MyEnum = new NetworkVariable<MyEnums>(m_MyEnumSettings);
    }

    public override void OnNetworkSpawn()
    {
        Debug.Log($"MyEnum is initialized with {MyEnum.Value}.");
        base.OnNetworkSpawn();
    }
}

Let me know if this helps you get past the issue you are having?

[JayPeet]

That is unfortunate, as for other types I have not had this happen. It would also mean that we need to duplicate the state.
In my use case, we are storing a TeamColor enum within the NetworkVariable, and that had a different default value depending on which Prefab it was. This has been working for me for a very long time, upwards of 6 months.

For now I have fixed it not being able to render the NetworkVariable by removing IEquatable from RenderNetworkContainerValueType. I have also split the RenderNetworkContainerValueType into two separate functions, one for NetworkLists and one for anything else. These changes can be seen here: 8cde93b

I am confused by the behavior you described, since my game had been using NetworkVariable for a while. After implementing my changes to the rendering code, they still retain their editor set values when entering playmode / the clients get the values sent to them.

Maybe I am misunderstanding what you said above?

[NoelStephensUnity]

@JayPeet
Well, actually I believe that I am the one who is misunderstanding... 😸
You are talking about this issue:

            if (genericType.IsValueType)
            {
                var method = typeof(NetworkBehaviourEditor).GetMethod("RenderNetworkContainerValueType", BindingFlags.Public | BindingFlags.Instance | BindingFlags.FlattenHierarchy | BindingFlags.NonPublic);
                var genericMethod = method.MakeGenericMethod(genericType);
                genericMethod.Invoke(this, new[] { (object)index });
            }

Have you tried just changing the instantiation from declaration to Awake like it is below?

public class ReproBehaviour : NetworkBehaviour
{
    public enum MyEnum
    {
        A,
        B,
        C
    }

    public NetworkVariable<MyEnum> myEnum;
    public int anotherInt;

    private void Awake()
    {
        myEnum = new NetworkVariable<MyEnum>();
    }
}

(the above throws no exceptions and works...at least it did for me)
The editor modifications I will try to get to (this week is going to be super busy, but I will try to take a gander).

Still...it is an issue as nothing should throw exceptions like that so my apologies for marking it as support and removing the bug status... sort of a support (work around to not get the exception based on my better understanding of what you are wanting) and a bug because it shouldn't throw and exception in the editor like that. 👍