SpawnManager.InstantiateAndSpawn doesn't Instantiate on Server

[AsmPrgmC3]

Description

SpawnManager.InstantiateAndSpawn doesn't instantiate the prefab when run on a server.

Reproduce Steps

1. Add a cube to the scene with a Network Object component
2. Create a prefab from that cube and add it to the Network Prefab list; remove the original from the scene
3. Add an empty to the scene and add the following component:

using Unity.Netcode;
using UnityEngine;

[RequireComponent(typeof(NetworkObject))]
public class Spawner : NetworkBehaviour
{
    public NetworkObject prefab;

    public override void OnNetworkSpawn()
    {
        if (!IsServer)
        {
            return;
        }

        NetworkManager.SpawnManager.InstantiateAndSpawn(prefab);
        NetworkManager.SpawnManager.InstantiateAndSpawn(prefab);
    }
}

4. Assign the cube prefab to the Spawner component
5. Start the project as a server (not host)

Actual Outcome

The cube prefab never gets instantiated, causing:

• No cubes get added to the scene/hierarchy
• (Inside the Editor only) The first InstantiateAndSpawn causes the error Transform resides in a Prefab asset and cannot be set to prevent data corruption
• The second InstatiateAndSpawn causes the error SpawnStateException: Object is already spawned

Expected Outcome

Two cubes spawn.

Environment

• OS: Windows 10 (22H2)
• Unity Version: 2022.3.7f1
• Netcode Version: Release 1.8.1

[NoelStephensUnity]

@AsmPrgmC3
Indeed this does look like a bug and we need to make sure our integration tests includes testing server only.
Unless you are using overrides for your prefabs, you can set forceOverride to true and it should when running as a server:

using Unity.Netcode;
using UnityEngine;

[RequireComponent(typeof(NetworkObject))]
public class Spawner : NetworkBehaviour
{
    public NetworkObject prefab;

    public override void OnNetworkSpawn()
    {
        if (!IsServer)
        {
            return;
        }

        NetworkManager.SpawnManager.InstantiateAndSpawn(prefab, forceOverride: true);
        NetworkManager.SpawnManager.InstantiateAndSpawn(prefab, forceOverride: true);
    }
}

This would be a temporary work around until the next update. The fix for this is pretty simple so I am going to go out on a limb and say the fix will be in the next update (whatever version we end up with that proceeds v1.9,1).

Thank you for the detailed information! 👍

[luke-youngmin-cho]

@AsmPrgmC3 실제로 이것은 버그처럼 보이고 통합 테스트에 테스트 서버만 포함되도록 해야 합니다. 프리팹에 오버라이드를 사용하지 않는 한, forceOverride를 true로 설정할 수 있으며 서버로 실행할 때 설정해야 합니다.

using Unity.Netcode;
using UnityEngine;

[RequireComponent(typeof(NetworkObject))]
public class Spawner : NetworkBehaviour
{
    public NetworkObject prefab;

    public override void OnNetworkSpawn()
    {
        if (!IsServer)
        {
            return;
        }

        NetworkManager.SpawnManager.InstantiateAndSpawn(prefab, forceOverride: true);
        NetworkManager.SpawnManager.InstantiateAndSpawn(prefab, forceOverride: true);
    }
}

이것은 다음 업데이트까지 임시로 해결할 수 있는 문제입니다. 이 문제에 대한 해결책은 매우 간단하므로, 저는 다음 업데이트( v1.9,1로 진행될 버전 )에 해결책이 포함될 것이라고 단언합니다.

자세한 정보 감사합니다! 👍

I tested it, but it doesn't seem to have been fixed yet.
Still have same bug. i have to set true for forceOverride parameter when running server.

[Moe-Baker]

This is still broken in 1.10.0, the latest version available for Unity 2022 LTS.
The 1.10.0 version was released by the end of July, this issue was open since the first of May, how is this still an issue guys?

[NoelStephensUnity]

This is resolved in v1.12.2 (#3202) and v2.2.0 (#3200).