Test: System.Threading.Tasks.Tests.AsyncValueTaskMethodBuilderTests/AwaitOnCompleted_InvokesStateMachineMethods failed with "Xunit.Sdk.EqualException"

Opened on behalf of @JiayiLi1

The test System.Threading.Tasks.Tests.AsyncValueTaskMethodBuilderTests/AwaitOnCompleted_InvokesStateMachineMethods(awaitUnsafe: False) has failed.

Assert.Equal() Failure\r
Expected: System.Threading.Tasks.Tests.AsyncValueTaskMethodBuilderTests+DelegateStateMachine\r
Actual: (null)

    Stack Trace:

       at System.Threading.Tasks.Tests.AsyncValueTaskMethodBuilderTests.<AwaitOnCompleted_InvokesStateMachineMethods>d__7.MoveNext() in E:\A\_work\887\s\corefx\src\System.Threading.Tasks.Extensions\tests\AsyncValueTaskMethodBuilderTests.cs:line 112
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() in f:\dd\ndp\fxcore\CoreRT\src\System.Private.CoreLib\src\System\Runtime\ExceptionServices\ExceptionDispatchInfo.cs:line 61
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess() in f:\dd\ndp\fxcore\CoreRT\src\System.Private.CoreLib\src\System\Runtime\CompilerServices\TaskAwaiter.cs:line 178
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification() in f:\dd\ndp\fxcore\CoreRT\src\System.Private.CoreLib\src\System\Runtime\CompilerServices\TaskAwaiter.cs:line 147
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() in f:\dd\ndp\fxcore\CoreRT\src\System.Private.CoreLib\src\System\Runtime\ExceptionServices\ExceptionDispatchInfo.cs:line 61
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess() in f:\dd\ndp\fxcore\CoreRT\src\System.Private.CoreLib\src\System\Runtime\CompilerServices\TaskAwaiter.cs:line 178
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification() in f:\dd\ndp\fxcore\CoreRT\src\System.Private.CoreLib\src\System\Runtime\CompilerServices\TaskAwaiter.cs:line 147
   at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd() in f:\dd\ndp\fxcore\CoreRT\src\System.Private.CoreLib\src\System\Runtime\CompilerServices\TaskAwaiter.cs:line 119
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() in f:\dd\ndp\fxcore\CoreRT\src\System.Private.CoreLib\src\System\Runtime\ExceptionServices\ExceptionDispatchInfo.cs:line 61
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess() in f:\dd\ndp\fxcore\CoreRT\src\System.Private.CoreLib\src\System\Runtime\CompilerServices\TaskAwaiter.cs:line 178
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification() in f:\dd\ndp\fxcore\CoreRT\src\System.Private.CoreLib\src\System\Runtime\CompilerServices\TaskAwaiter.cs:line 147

Build : Master - 20170724.01 (UWP ILC Tests)
Failing configurations:

• Windows.10.Amd64.ClientRS3-x64
  • Release
  • Debug
• Windows.10.Amd64.ClientRS3-x86
  • Debug
  • Release

Detail: https://mc.dot.net/#/product/netcore/master/source/official~2Fcorefx~2Fmaster~2F/type/test~2Ffunctional~2Filc~2F/build/20170724.01/workItem/System.Threading.Tasks.Extensions.Tests/analysis/xunit/System.Threading.Tasks.Tests.AsyncValueTaskMethodBuilderTests~2FAwaitOnCompleted_InvokesStateMachineMethods(awaitUnsafe:%20False)

[danmoseley]

@kouvel can you take a look?

[joshfree]

/cc @AntonLapounov since this is ILC and not CoreCLR

[danmoseley]

@AntonLapounov did you investigate? Is this only a test issue?

still failing: https://mc.dot.net/#/product/netcore/uwp60/source/official~2Fcorefx~2Frelease~2Fuwp6.0~2F/type/test~2Ffunctional~2Filc~2F/build/20170807.01/workItem/System.Threading.Tasks.Extensions.Tests

[AntonLapounov]

@danmosemsft I cannot reproduce the issue neither on RS2 nor on RS3 (UWPDogFood-d15prerel-26803_3009-Enterprise image). It seems that AwaitOnCompleted does not call IAsyncStateMachine.SetStateMachine for some reason, but I am not sure how to investigate it further without a local repro.

[danmoseley]

Perhaps try the repro tool, if you haven't already. @tijoytom can point at instructions.

[safern]

@AntonLapounov any progress on this failure? We are getting closer to have a green test run in release branch and this is one of the pending test failures.

[adityamandaleeka]

I'm able to repro this locally. I'll assign it to myself and start investigating.

[safern]

Thanks @adityamandaleeka really appreciate your help :)

[adityamandaleeka]

I think I know what's going on here. Will post more details later.

[adityamandaleeka]

OK, so the issue here seems to be in the AsyncMethodBuilder code for uapaot. In GetCompletionActionHelper, there's a line where we call SetStateMachine after the part where we box the state machine. However, the SetStateMachine call is under #if DEBUG for some reason, so it fails on all our runs because they use the Release version of S.P.CoreLib.

I'm trying to understand the history behind why this code is this way, and whether we should change it. For what it's worth, enabling that line for Release fixes the test.

I'll update and/or fix this issue when I have more info.