Unity MPM - Prefab Id XYZ not found - after modifying a prefab in main player.

[FirstGearGames]

Issue to be investigated/confirmed.

Requires reload domain to be off

1. Load the game scene in /Scenes/GameScene,
2. Go to Window/Multiplayer/Multiplayer Play Mode,
3. Enable the Player 2 editor (see image below).
4. Start editor1 as host. Start editor2(MPM) as client.
5. Stop play mode,
6. Update the speed to the player prefab in /Prefabs/Player,
7. Save prefab.
8. Repeat step 4 and see error.

MPMIssue.zip

[FirstGearGames]

Planned investigation shortly after the release of 4.6.9

[FirstGearGames]

Resolved in 4.6.10

Worth noting that you were making a copy of DefaultPrefabObjects, which you should not be doing as those are managed by FishNet. That was not the cause of the problem but I can see it causing other issues. I'll add a block in for 4.6.10 against that.

[FirstGearGames]

Fix:
Open file Configurating.cs and replace entire contents with this.

using System.IO;
using System.Xml.Serialization;
using UnityEngine;
using UnityEditor.Compilation;
using UnityEditor.Build.Reporting;
using UnityEditor;
using UnityEditor.Build;

namespace FishNet.Configuring
{
    public class Configuration
    {
        public enum CloneType
        {
            None = 0,
            UnityMultiplayer = 1,
            ParrelSync = 2,
        }

#if UNITY_EDITOR
        /// <summary>
        /// </summary>
        private static ConfigurationData _configurations;
        /// <summary>
        /// ConfigurationData to use.
        /// </summary>
        public static ConfigurationData Configurations
        {
            get
            {
                if (_configurations == null)
                    _configurations = LoadConfigurationData();
                if (_configurations == null)
                    throw new("Fish-Networking Configurations could not be loaded. Certain features such as code-stripping may not function.");
                return _configurations;
            }
            private set { _configurations = value; }
        }
        /// <summary>
        /// File name for configuration disk data.
        /// </summary>
        public const string CONFIG_FILE_NAME = "FishNet.Config.XML";
#endif

        /// <summary>
        /// Returns true if this editor is a multiplayer clone.
        /// </summary>
        /// <returns></returns>
        public static bool IsMultiplayerClone(out CloneType cloneType)
        {
            //Not editor, not a clone.
#if !UNITY_EDITOR
            cloneType = CloneType.None;
            return false;
#endif

            /* Beyond here is only run if editor. */


            if (Application.dataPath.ToLower().Contains("library/vp/"))
            {
                cloneType = CloneType.UnityMultiplayer;
                return true;
            }

#if PARRELSYNC
            if (ParrelSync.ClonesManager.IsClone())
            {
                cloneType = CloneType.ParrelSync;
                return true;
            }
#endif
            
            cloneType = CloneType.None;

            return false;
        }

        /// <summary>
        /// Returns the path for the configuration file.
        /// </summary>
        /// <returns></returns>
        internal static string GetAssetsPath(string additional = "")
        {
#if !UNITY_EDITOR
            return string.Empty;
#else
            string a = Path.Combine(Directory.GetCurrentDirectory(), "Assets");
            if (additional != "")
                a = Path.Combine(a, additional);
            return a;
#endif
        }

        /// <summary>
        /// Returns FishNetworking ConfigurationData.
        /// </summary>
        /// <returns></returns>
        internal static ConfigurationData LoadConfigurationData()
        {
#if !UNITY_EDITOR
            return null;
#else
            // return new ConfigurationData();
            if (_configurations == null || !_configurations.Loaded)
            {
                string configPath = GetAssetsPath(CONFIG_FILE_NAME);
                // string configPath = string.Empty;
                // File is on disk.
                if (File.Exists(configPath))
                {
                    FileStream fs = null;
                    try
                    {
                        XmlSerializer serializer = new(typeof(ConfigurationData));
                        fs = new(configPath, FileMode.Open, FileAccess.Read, FileShare.Read);
                        _configurations = (ConfigurationData)serializer.Deserialize(fs);
                    }
                    finally
                    {
                        fs?.Close();
                    }
                    _configurations.Loaded = true;
                }
                else
                {
                    // If null then make a new instance.
                    if (_configurations == null)
                        _configurations = new();
                    // Don't unset loaded, if its true then it should have proper info.
                    // _configurationData.Loaded = false;
                }
            }

            return _configurations;
#endif
        }
    }
}

Open DelayedEditorTasks.cs and this section.

        static DelayedEditorTasks()
        {
            if (Configuration.IsMultiplayerClone())

Replace with this.

        static DelayedEditorTasks()
        {
            if (Configuration.IsMultiplayerClone(out _))
                return;

Open NetworkManager.cs and find this line.

bool isDefaultPrefabs = SpawnablePrefabs != null && SpawnablePrefabs is DefaultPrefabObjects;

Add the following immediately after.

Configuration.IsMultiplayerClone(out Configuration.CloneType cloneType);

Right below you will find #if UNITY_EDITOR.
Replace the entire block starting with the #if, ending with the #endif with this.

#if UNITY_EDITOR
            /* If first instance then force
             * default prefabs to repopulate.
             * This is only done in editor because
             * cloning tools sometimes don't synchronize
             * scriptable object changes, which is what
             * the default prefabs is. */

            /* There is an issue with Unity Multiplayer where if a prefab
             * is modified in the main editor with a multiplayer window open,
             * the modified prefab becomes null in the collection. Because of this,
             * we must re-generate on the cloned window. */
            if (isDefaultPrefabs && (cloneType == Configuration.CloneType.UnityMultiplayer || (_refreshDefaultPrefabs && _instances.Count == 0)))
            {
                Generator.IgnorePostProcess = true;
                Debug.Log("DefaultPrefabCollection is being refreshed.");
                Generator.GenerateFull(initializeAdded: false);
                Generator.IgnorePostProcess = false;
            }
#endif

[childtoyz]

hi the issue still persists. (4.6.12)

If you reorder an object in the prefabObject list, it temporarily fixes the issue, but as soon as you make any further changes to the prefab, the problem comes back.

[FirstGearGames]

This is 1000% a Unity issue not synchronizing certain file changes across mutliplayer mode, but we might be able to patch it.

Can you please DM me with this issue so we can troubleshoot in real time.

[FirstGearGames]

Reopened -- issue persist when not using generated prefabs.

[FirstGearGames]

This is probably going to have to get set to low priority. I reviewed the code changes to FN and they are working properly, but something changed between a Unity version at some point where it no longer works.

I do not want to spend too much time fighting Unity on this with other bugs open.