Setup Nullable reference type in Unity

🎯 What is Nullable reference type?

Nullable reference type explicitly specifies whether a variable must contain a value or may not.

Key Features

• Design-time analysis
• Explicit API contracts
• Search for potential locations with NullReference

📑 Software requirements

• .NET Standard 2.1+
• Unity 2021+

📃 How to turn on static analysis

To analyze the individual assemblies

Create a csc.rsp file next to the asmdef:

Add the nullable argument to the contents of csc.rsp:

-nullable:enable

To analyze individual .cs files

Add the #nullable annotation context to the .cs content:

#nullable enable

💻 Migration Guide

What to do with Unity UI bindings and DI Inject attributes?

Explicitly tell the analyzer that you guarantee their assignment and suppress the warnings using the ! null-forgiving operator.

Unity UI example:

[SerializeField] private Image _image = null!;

VContainer DI example:

namespace Sandbox.Domain
{
    private MoveController _moveController = null!;

    [Inject]
    public void Init(MoveController moveController)
    {
        _moveController = moveController;
    }
}

To exclude a separate part of the code from analysis, you can use the following annotation:

#nullable disable

using System;

namespace Sandbox.Server.Responses
{
    [Serializable]
    public class UserResponse
    {
        public int Id;
        public string Name;
    }
}

🎁 Helpful Links

Nullable reference types in Unity

Microsoft guide