Productize ManualResetValueTaskSource

[stephentoub]

As called out in dotnet/corefx#29468, we should design/expose ManualResetValueTaskSource{Logic} (https://github.com/dotnet/corefx/blob/master/src/Common/tests/System/Threading/Tasks/Sources/ManualResetValueTaskSource.cs), and potentially an auto-reset equivalent. The manual-reset variety is likely to be used by async iterators generated by the C# compiler, and the auto-reset variety would be needed if we wanted to replace implementations already in use in corefx (e.g. in Socket).

[stephentoub]

Replaced by https://github.com/dotnet/corefx/issues/32664

[AndreasHeisel]

Hello @stephentoub,

I have investigated ManualResetValueTaskSource if it can help avoiding allocations in my code. It is an awesome piece of code but I do miss one thing:

TaskCompletionSource has a constructor that accepts a TaskCreationOptions value. The one I miss is RunContinuationsAsynchronously - for the same reasons it was added to TaskCreationOptions.

https://blogs.msdn.microsoft.com/pfxteam/2015/02/02/new-task-apis-in-net-4-6/

[stephentoub]

TaskCompletionSource has a constructor that accepts a TaskCreationOptions value. The one I miss is RunContinuationsAsynchronously

The ManualResetValueTaskSourceCore from https://github.com/dotnet/corefx/issues/32664 has a RunContinuationsAsynchronously property.

[AndreasHeisel]

Ok, my fault. I used an older version. Thank you

[stephentoub]

😄

[AndreasHeisel]

Is there a way to see if GetResult() was called? I mean how do I know when it is safe to call Reset() and when I must allocate a new ManualResetValueTaskSource{?

[stephentoub]

You can track that yourself in whatever code wraps this struct. Your wrapper is what actually implements the interface, and thus it's actually your GetResult method that's called (and you then call he struct's GetResult), so you can keep track of that.

[AndreasHeisel]

So I have to use ManualResetValueTaskSourceLogic to track it. The class version ManualResetValueTaskSource doesn't track. Correct?

[stephentoub]

The class version ManualResetValueTaskSource doesn't track

We're not currently planning to ship the class version. If we do, we could decide whether to track it or not.

[AndreasHeisel]

Understood, thank you