NewtonsoftJson DLL Hell (especially for modding Unity games)

[mortarroad]

General Problem

A lot of apps and libraries use NewtonsoftJson. So does buttplug-csharp

But there are a few problems:

• buttplug-csharp brings its own version of NewtonsoftJson (currently 13.0.4)
• a lot of .NET apps already bring their own version of NewtonsoftJson
  • in particular, in Unity games, an unofficial build seems to be common? (https://docs.unity3d.com/Packages/com.unity.nuget.newtonsoft-json@3.2; latest seems to be 13.0.2)
• NewtonsoftJson does not seem to be forward compatible in some cases (see below)
• as far as I know, only one version of the library can be loaded

This is a problem for modding. The version conflict can lead to errors at runtime, even if the DLL is loaded fine at first.

My Specific Problem

The latest buttplug-csharp version (5.0.1-beta2, 08b2928) does not work with the game I'm trying to mod.

I'm getting the following error when calling ConnectAsync():

MissingMethodException: Method not found: string Newtonsoft.Json.Linq.JToken.ToString(Newtonsoft.Json.Formatting)
Stack trace:
Buttplug.Client.ButtplugConnectorJSONParser.Serialize (Buttplug.Core.Messages.ButtplugMessage msg) (at Buttplug/Client/ButtplugConnectorJSONParser.cs:29)
Buttplug.Client.ButtplugRemoteJSONConnector.PrepareMessage (Buttplug.Core.Messages.ButtplugMessage msg, System.Threading.CancellationToken token) (at Buttplug/Client/ButtplugRemoteJSONConnector.cs:41)
Buttplug.Client.ButtplugWebsocketConnector.SendAsync (Buttplug.Core.Messages.ButtplugMessage msg, System.Threading.CancellationToken cancellationToken) (at Buttplug/Client/ButtplugWebsocketConnector.cs:103)
Buttplug.Client.ButtplugClientMessageHandler.SendMessageAsync (Buttplug.Core.Messages.ButtplugMessage msg, System.Threading.CancellationToken token) (at Buttplug/Client/ButtplugClientMessageHandler.cs:35)
Buttplug.Client.ButtplugClient.ConnectAsync (Buttplug.Client.IButtplugClientConnector connector, System.Threading.CancellationToken token) (at Buttplug/Client/ButtplugClient.cs:133)

The issue is, that an overload of JToken.ToString() has been added between NewtonsoftJson release 13.0.4 and 13.0.2:

• in 13.0.2, there is:
  • ToString()
  • ToString(Formatting formatting, params JsonConverter[] converters)
• in 13.0.4, there is:
  • ToString()
  • ToString(Formatting formatting) <-- this overload is new
  • ToString(Formatting formatting, params JsonConverter[] converters)

While I believe that this is a bug in NewtonsoftJson (because it breaks compatibility in a patch release), I think we have to deal with it now. The versions are already released and used in games.

Solution?

Is there a recommended way to deal with this?

I can see the following possible solutions:

• ensure buttplug-csharp is compatible with a wide range of versions of NewtonsoftJson (how?)
• vendor NewtonsoftJson / rename the dependency to avoid conflicts
• use a different / custom JSON library

In my case, I was able to "fix" it by compiling buttplug-csharp myself and setting the NewtonsoftJson version to exactly the same version that the game uses when compiling. But that means I have to use a custom build.

[qdot]

Yeah this has been a problem since just about forever and it sucks, esp because a lot of our Unity users aren't really familiar with resolving this. The plan at the moment is to take the idea LoveMachine (the Illusion mod) has and use https://github.com/LitJSON/litjson instead, which can be compiled into the library so we can just avoid this altogether.