[Edge Case] Actor Context might not be available inside ReceiveAsync

[Arkatufus]

This is an edge case reproduction where Context.Self (and by proxy, Context.Sender) can not be accessed inside ReceiveAsync() if async context were somehow lost.

This unit test is meant to emulate what happens if a callback function/action that accesses the actor IActorContext were being called inside a pre-compiled third party library and it uses even a single call to await SomeFunction().ConfigureAwait(false); before the callback were invoked.

This is the output of the unit test:

Xunit.Sdk.XunitException
10 Exception(s) was thrown while actors were processing messages.
    actor: worker_5, exception: There is no active ActorContext, this is most likely due to use of async operations from within this actor.
    actor: worker_3, exception: There is no active ActorContext, this is most likely due to use of async operations from within this actor.
    actor: worker_2, exception: There is no active ActorContext, this is most likely due to use of async operations from within this actor.
    actor: worker_8, exception: There is no active ActorContext, this is most likely due to use of async operations from within this actor.
    actor: worker_6, exception: There is no active ActorContext, this is most likely due to use of async operations from within this actor.
    actor: worker_7, exception: There is no active ActorContext, this is most likely due to use of async operations from within this actor.
    actor: worker_4, exception: There is no active ActorContext, this is most likely due to use of async operations from within this actor.
    actor: worker_0, exception: There is no active ActorContext, this is most likely due to use of async operations from within this actor.
    actor: worker_1, exception: There is no active ActorContext, this is most likely due to use of async operations from within this actor.
    actor: worker_9, exception: There is no active ActorContext, this is most likely due to use of async operations from within this actor.
   at Akka.Tests.Dispatch.ActorAsyncAwaitSpec.ReceiveActorSelfInsideAsyncCallback() in D:\git\akkadotnet\akka.net\src\core\Akka.Tests\Dispatch\AsyncAwaitSpec.cs:line 405
   at Xunit.Sdk.TestInvoker`1.<>c__DisplayClass48_0.<<InvokeTestMethodAsync>b__1>d.MoveNext() in /_/src/xunit.execution/Sdk/Frameworks/Runners/TestInvoker.cs:line 276
--- End of stack trace from previous location ---
   at Xunit.Sdk.ExecutionTimer.AggregateAsync(Func`1 asyncAction) in /_/src/xunit.execution/Sdk/Frameworks/ExecutionTimer.cs:line 48
   at Xunit.Sdk.ExceptionAggregator.RunAsync(Func`1 code) in /_/src/xunit.core/Sdk/ExceptionAggregator.cs:line 90


Received 10 messages within 10.0447699 seconds. Expected message counts: 20

[Arkatufus]

Self review

[Arkatufus]

Note that this unit test will run just fine if we remove .ConfigureAwait(false), but of course users would likely be stuck with code that uses .ConfigureAwait(false) if they were using a third party package.

[Arkatufus]

Note that this problem can be prevented if we close Self inside the message handler.