Unusual Error in version 1.5.1

[Reag]

Description

Project fails to compile after updating to 1.5.1

Reproduce Steps

Update to version 1.5.1

Actual Outcome

Receive a code generation error (Looks related to that null ref check that was added)

Expected Outcome

Project works

Screenshots

Unity.Netcode.Editor.CodeGen.NetworkBehaviourILPP: (0,0): error - System.NullReferenceException: Object reference not set to an instance of an object.|| at Unity.Netcode.Editor.CodeGen.NetworkBehaviourILPP.GenerateVariableInitialization(TypeDefinition type)|| at Unity.Netcode.Editor.CodeGen.NetworkBehaviourILPP.GenerateVariableInitialization(TypeDefinition type)|| at Unity.Netcode.Editor.CodeGen.NetworkBehaviourILPP.ProcessNetworkBehaviour(TypeDefinition typeDefinition, String[] assemblyDefines)|| at Unity.Netcode.Editor.CodeGen.NetworkBehaviourILPP.<>c__DisplayClass7_0.<Process>b__1(TypeDefinition b)|| at System.Collections.Generic.List1.ForEach(Action1 action)|| at Unity.Netcode.Editor.CodeGen.NetworkBehaviourILPP.Process(ICompiledAssembly compiledAssembly) at Unity.Netcode.Editor.CodeGen.NetworkBehaviourILPP.GenerateVariableInitialization(TypeDefinition type)|| at Unity.Netcode.Editor.CodeGen.NetworkBehaviourILPP.GenerateVariableInitialization(TypeDefinition type)|| at Unity.Netcode.Editor.CodeGen.NetworkBehaviourILPP.ProcessNetworkBehaviour(TypeDefinition typeDefinition, String[] assemblyDefines)|| at Unity.Netcode.Editor.CodeGen.NetworkBehaviourILPP.<>c__DisplayClass7_0.<Process>b__1(TypeDefinition b)|| at System.Collections.Generic.List1.ForEach(Action1 action)|| at Unity.Netcode.Editor.CodeGen.NetworkBehaviourILPP.Process(ICompiledAssembly compiledAssembly)

Environment

• OS: Windows
• Unity Version: 2022.3.0
• Netcode Version: 1.5.1

Additional Context

Really sorry about the super short bug report. My team is on a very tight deadline right now, so I only had 30 min to tests the new netcode version update. Hopefully what I posted above is helpful!

[PitouGames]

Same error for me. I don't know yet which script is causing this in my project.

Environment

• OS: Windows 11
• Unity Version: 2021.3.22f1
• Netcode Version: 1.5.1

[DatePest]

Hello friends, I also encountered this problem after upgrading today, I found the reason after trying it myself, I hope it can help you.
This code is changed from Singleton MonoBehaviour to a variant of NetworkBehaviour.
This method can be used in 1.4.0, but an error will occur in 1.5.1.
I found out that the problem was declaring the generic T variable,

private static T instance; //<T>
public static T Instance
     {
         get { return instance; }
     }

[PitouGames]

I can now confirm what @DatePest said.
This script caused the issue in my project. Add it to your assets and you will have the compilation bug (even without implementing concrete child classes).
This is a regression from 1.4.0.

using Unity.Netcode;
using UnityEngine;

/// <summary>
/// A NGO <see cref="NetworkBehaviour"/> singleton.
/// </summary>
/// <typeparam name="T">Type of the singleton</typeparam>
public abstract class NetworkBehaviourSingleton<T> : NetworkBehaviour where T : NetworkBehaviour
{
    public static T Instance { get; private set; }

    protected virtual void Awake()
    {
        if (Instance == null) {
            Instance = GetComponent<T>();
        } else {
            Debug.LogWarning($"[NetworkBehaviourSingleton] Created an other {typeof(T).Name} but one instance already exist!");
        }
    }
}

[deogo]

for those who are struggling, here is solution. The trick is to not use Generic type variables

public class SingletonNetwork<T> : NetworkBehaviour where T : NetworkBehaviour
{
    private static NetworkBehaviour _instance;
    public static T Instance { get => _instance as T; }

    public virtual void Awake()
    {
        if (_instance == null)
        {
            _instance = this;
        }
        else
        {
            Destroy(gameObject);
        }
    }
}

public class Derived : SingletonNetwork<Derived>
{
    private void Start()
    {
        var v = Derived.Instance;
    }
}

[Nakou]

I confirm the same regression.
since Unity 2022.3.4f doesn't let you chose the 1.4 version in the package manager, you can downgrade your version of NGO by changing
"com.unity.netcode.gameobjects": "1.5.1",
to
"com.unity.netcode.gameobjects": "1.4.0",
in your ProjectName/Packages/manifest.json