Unity serialization exception from NetworkConnection constructor after upgrading to Mirror 96.11.3

[lcompton]

Description

After upgrading Mirror from 96.11.2 to 96.11.3, I began getting repeated Unity serialization exceptions involving NetworkConnection.

Downgrading to Mirror 96.11.2 eliminates the exceptions without any other code changes.

Environment

• Unity: 6000.6.3f1
• Mirror: 96.11.3
• Last known working Mirror version: 96.11.2

Exception

UnityException: get_time is not allowed to be called during serialization, call it from Awake or Start instead. Called from MonoBehaviour 'NetworkIdentity' on game object 'Player'.
See "Script Serialization" page in the Unity Manual for further details.
Mirror.NetworkConnection..ctor () (at Assets/Mirror/Core/NetworkConnection.cs:65)
Mirror.NetworkConnectionToClient..ctor () (at Assets/Mirror/Core/NetworkConnectionToClient.cs:63)
UnityEngine.StackTraceUtility:ExtractStringFromExceptionInternal(Object, String&, String&)

Network prefab registration

One potentially relevant detail is that I do not maintain the network prefab list manually in the NetworkManager inspector.

My network prefabs are loaded as Addressables and registered programmatically using:

NetworkClient.RegisterPrefab(networkIdentity.gameObject);

This worked without the serialization exceptions under Mirror 96.11.2.

Reproduction / regression

I believe the following steps will reproduce the issue, although I haven't verified...

1. Create a project using Unity 6000.6.3f1.
2. Install Mirror 96.11.3.
3. Create a prefab with a NetworkIdentity.
4. Create a script that registers the prefab with NetworkClient.RegisterPrefab().
5. get_time is not allowed to be called during serialization exception occurs.

[lcompton]

One thing I neglected to mention is that the network prefab registration occurs in the process of warming a cache of ScriptableObjects loaded via the Addressables system. Here are the relevant C# files...
ConfigDefinition.cs
ConfigRegistry.cs

[MrGadget1024]

Which change in this commit do you think is the breaking change? Either add them individually from 11.2 or remove them from 11.3.

[lcompton]

Adding "[Serializable]" to NetworkConnection and NetworkConnectionToClient in 96.11.2 caused the exceptions to appear. I stopped there.

[MrGadget1024]

Adding "[Serializable]" to NetworkConnection and NetworkConnectionToClient in 96.11.2 caused the exceptions to appear. I stopped there.

Try 11.3 and change those to [System.NonSerialized] instead and see if that works.

[lcompton]

"[NonSerialized]" can only be applied to fields. I tried putting "[NonSerialized]" on "lastMessageTime". That did not solve the problem.

[MrGadget1024]

"[NonSerialized]" can only be applied to fields. I tried putting "[NonSerialized]" on "lastMessageTime". That did not solve the problem.

Might just have to remove the attributes and live with the annoying warnings from Unity.

[lcompton]

Perhaps there's an alternative to running Time.time in that constructor. Do those classes need to be Serializable?