Generic Wrapper Struct not Serializing Correctly

[dense sapphire]

Have I discoverd a Unity bug? Or am I doing something not allowed?

When I wrap an object in a generic wrapper struct, and then use that struct as a field in a MonoBehavior, the object being wrapped doesn't seem to serialize correctly.

For example, the Debug.Log() line in this example will always print "False", even when no Material is assigned.

{
    public Wrapper<Material> test;
}

[Serializable]
public struct Wrapper<T> : ISerializationCallbackReceiver where T : class
{
    [SerializeReference]
    public T target;

    public void OnBeforeSerialize()
    {
        Debug.Log(target == null);
    }

    public void OnAfterDeserialize()
    {
    }
}```

[jovial knot]

this might be the editor using fake null for serialized fields in MonoBehaviours, and because T isn't restricted to using UnityEngine.Object it's probably not using the custom == operator so the log is technically correct

section 1 of this would be relevant: https://unity.com/blog/engine-platform/custom-operator-should-we-keep-it

you might try making a small build and testing that

or maybe casting directly to material to test

[dense sapphire]

Oh, the editor uses fake nulls? I did not know!

Ty for this.

Yep, it looks like that was it. Switching to .Equals() for the check is now returning True.

[civic girder]

Equals() is what the == operator uses. You need to use ReferenceEquals() to bypass the unityengine.object override.

[wooden nacelle]

ReferenceEquals will return false on Wrapper<T> struct there unless you ref pass them

even when ref passing, you'd need unsafe to check the managed pointers like so Unsafe.AreSame<T>(ref TStruct, ref TStruct)

https://learn.microsoft.com/en-us/dotnet/api/system.runtime.compilerservices.unsafe.aresame?view=net-9.0#system-runtime-compilerservices-unsafe-aresame-1(-0@-0@)