Mono Upgrade UniRx Library with .Net 4.6 API Error

Unity Version 5.5.0xMono-Runtime-Upgrade-b9
API: .Net 4.6
UniRx Scripting Define Symbols
ENABLE_MONO_BLEEDING_EDGE_EDITOR;ENABLE_MONO_BLEEDING_EDGE_STANDALONE
Status: Works!

Unity Version 2017.1.0b10 & 2017.1.0b8
API: .Net 4.6
UniRx Scripting Define Symbols
ENABLE_MONO_BLEEDING_EDGE_EDITOR;ENABLE_MONO_BLEEDING_EDGE_STANDALONE
Status: Error!

Test Script EveryUpdateTest.cs

Code (CSharp):

1. using UniRx;
2. using UnityEngine;
3.  
4. public class EveryUpdateTest : MonoBehaviour {
5.     void Start () {
6.         Observable.EveryUpdate()
7.             .Subscribe(_ => Debug.Log("test") )
8.             .AddTo(this);
9.     }  
10. }

Other notes:
- I posted an issue report for the author of UniRx:
https://github.com/neuecc/UniRx/issues/230

- UniRx is a library that implements Rx interface (like the System.IObservable) which is now part of .Net 4.6. So using the compiler define symbols above is necessary.

- UniRx website: https://github.com/neuecc/UniRx

I am not sure if this is a UniRx or Unity problem, I can submit a Unity bug report with example project if needed.

 

I suspect UniRx sets up a synchronization context for the main thread. Unity now has its own one and calls it every frame:

Code (CSharp):

1. if (SynchronizationContext.Current != null)
2. {
3.     ((UnitySynchronizationContext)SynchronizationContext.Current).Exec();
4. }

If the current synchronization context if not UnitySynchronizationContext, we get invalid cast exception. Unity could change this code to

Code (CSharp):

1. var context = SingleThreadSynchronizationContext.Current as UnitySynchronizationContext;
2. context?.ExecuteTasks();

to manage such cases. However, I'm not sure that overriding the Unity's context with a custom one may be considered as a good idea. I guess, it's not.

 

Bug # 924070