Multiplayer Play Mode 1.0 fails to reload domain under specific circumstances

[Yoraiz0r]

Description

I've tried using Multiplayer Play Mode, with Domain Reload disabled, and noticed that when I make code changes, the domain is not reloaded for the additional players at certain times.

After some experimentation, I've determined the problem comes through its interaction with the Jetbrains Rider Editor.

The problem was perceived such that when changing any code with Rider (such as Debug.Log("A") to B), the primary editor reloads domain properly, but other editors will not reload domain.

Attempting the same process with Visual Studio code properly reloads domains for other editors.

To understand what is going wrong with the interaction, I've locally pulled both the Jetbrains Rider Editor package and the Multiplayer Play Mode package.

Jetbrains Rider seems to be innocent in this case, only asking for an assets refresh.

Multiplayer Play Mode fails under its lambda event for vpContext.MainEditorSystems.AssetImportEvents.RequestImport, in Unity.Multiplayer.Playmode.VirtualProjects.Editor.MainEditorInternalRuntime.HandleEvents.
Specifically, it fails under this this section

                if (numAssetsChanged == 0)
                {
                    MppmLog.Debug("No assets to actually sync with clones.");
                    return;
                }

If the code is changed through visual studio, the numAssetsChanged is 1, but if Jetbrains Rider handles the code change, the event is only raised with numAssetsChanged being 0.

This numAssetsCheck seems erronous to me, since didDomainReload is set to true.

For now, I'm opting to locally solve this by changing this query to if (numAssetsChanged == 0 && !didDomainReload), which resolves the problems.

Reproduce Steps

1. Create a new Unity project, with the Jetbrains Rider Editor and Multiplayer Play Mode packages installed.
2. Create a MonoBehaviour with Start() { Debug.Log("A"); } and add it to a gameobject in an open scene.
3. In the Project Settings/Editor/Enter Play Mode Settings enable Enter Play Mode Options and disable Domain Reload.
4. Open Multiplayer Play Mode and enable a second player.
5. Enter Play Mode, and witness both players logging "A".
6. Exit Play Mode
7. Using Jetbrains Rider, edit "A" to "B", and witness that only the primary player reloads domain.
8. Enter Play Mode, and witness the primary player logging "B" while the second player logs "A".

Actual Outcome

Primary player reloads domain, but second player does not.

Expected Outcome

Both players reload domain, when code changes.

Environment

• OS: Windows 10
• Unity Version: 6000.0.0b13
• Netcode Version: None, this is a Multiplayer Play Mode issue regardless of netcode.
• Multiplayer Play Mode Version: 1.0.0.
• Jetbrains Rider Editor version: 3.0.28.

[van800]

This issue was also reported in the Rider bugtracker https://youtrack.jetbrains.com/issue/RIDER-111671/Riders-asset-refresh-on-code-change-does-not-trigger-Unitys-Multiplayer-Play-Modes-recompilation
I haven't found a way for work-arounding it on the Rider package side. Please see details in the YouTrack issue.

[kyubuns]

me too.
I think it's a very fatal bug, but has the development team not reproduced it?

I'm using Unity6000.0.14f1 + com.unity.multiplayer.playmode 1.3.0-pre.1 + Rider 2024.1.4.

[BanhmiDev]

I've had this issue ever since trying out Multiplayer Play Mode, never thought its because of disabling domain reload on play. Seems like this isn't a high priority due to not a lot of people disabling the setting or is there another open issue that can be bumped?

[NoelStephensUnity]

You should update to the most current version of MPPM (v1.3.3) to resolve any domain/AssetDatabase synchronization issues between MPPM virtual client instances and the primary editor instance. 👍

2025-04-11.16-15-35.mp4