VSTHRD103 fired on Task.WaitAll

[AlexanderHawliczek]

Bug description

VSTHRD103 complains on:
Task.WaitAll(taskLArray, CancellationToken.None);
suggesting
Task.await(taskList.ToArray(), CancellationToken.None);

Repro steps

Task.WaitAll(someTaskArray, CancellationToken.None);

Expected behavior

do nothing

Actual behavior

Corrects to
Task.await(someTaskArray, CancellationToken.None);

• Version used: 17.0.64
• Application (if applicable): VS Studio 2022 prof

[AArnott]

I can't repro this.

No warnings appear.

What you say the analyzer is suggesting doesn't make any sense. I don't think the code fix would know how to add .ToArray() to the first argument or change taskLArray to taskList.

Having one of our analyzers recommend Task.WhenAll over Task.WaitAll, particularly while inside an async method, would be by design.

[AlexanderHawliczek]

My apologies. I mixed it up.
I was able to recreate it right away with VS 2019 .Net 5
Version 17.0.64

Original

    public async Task DummyAsync()
    {
      var taskArray = new Task[1] { new Task(() => Console.WriteLine("")) };
      Task.WaitAll(taskArray, CancellationToken.None);
    }

Result

    public async Task DummyAsync()
    {
      var taskArray = new Task[1] { new Task(() => Console.WriteLine("")) };
      await Task;
    }

Btw if the method is a simple void, it almost gets it right:
Original non async method

    public void DummyAsync()
    {
      var taskArray = new Task[1] { new Task(() => Console.WriteLine("")) };
      Task.WaitAll(taskArray, CancellationToken.None);
    }

Changed

    public async Task DummyAsync()
    {
      var taskArray = new Task[1] { new Task(() => Console.WriteLine("")) };
      await Task.WhenAll(taskArray, CancellationToken.None);
    }

Just the CancellationToken.None breaks the code. Works fine if token is not in original

[AArnott]

Thanks for the better code snippets. I still cannot repro though. What version of the microsoft.visualstudio.threading.analyzers package are you using? Consider sending a zip of your minimal repro project if that's easier.

[AlexanderHawliczek]

Here you go.
New simple console project only the VS threading package added
Microsoft-VS-Threading-Issue.zip

On an additional example I found this

Stack trace is in the project at the example causing it.

[AArnott]

Perfect. These all repro for me. I'll keep this around and turn each of these into unit tests in the repo to fix them up.

[hcoona]

ping