Assert.ThatAsync doesn't seem to work with ValueTask

[OsirisTerje]

Twitter user eduardo @ed_dev_ commented about this, and showed the following repro code:

See twitter post https://twitter.com/ed_dev_/status/1730951076730323419

Comments @manfred-brands @stevenaw @jnm2 ?

Repro here: https://github.com/nunit/nunit.issues/tree/main/Issue4588

[eduherminio]

Adding workaround as well:

await Assert.ThatAsync(() => Method(), Is.EqualTo(""));   // Doesn't work, would work if method returned Task<string>
await Assert.ThatAsync(async () => await Method(), Is.EqualTo(""));  // Works

[OsirisTerje]

Another workaround is

await Assert.ThatAsync(()=>Method().AsTask(),Is.EqualTo(""));

[jnm2]

I'm not sure where, but I'd thought we had an existing thread on ValueTask. ValueTask is just one of dozens of awaitable types other than Task. () => Task.Yield() is an example, and so is UWP's IAsyncOperation.

For all of these, async () => await seems quite tolerable. I still think it's good advice to add async/await even when it's not strictly necessary: https://blog.stephencleary.com/2016/12/eliding-async-await.html

With that said, of course ValueTask is much more common as an awaitable method return type than anything else besides Task itself, so maybe we could consider adding extra API overloads just for convenience.

[manfred-brands]

After re-reading Stephen Toubs article I also think ValueTask will become more in use and a specific overload could be useful. Due to the limitations described in the article it could be that we have to call AsTask() and then call the original API.

[OsirisTerje]

@jnm2 We do have other issues on ValueTask. You authored one back in 2018. I'll link these together.

But this one was very specific, so I thought it was a valid one to keep.

[OsirisTerje]

@jnm2 Here are all the async issues, open and closed. I have had them collected in a project. https://github.com/nunit/nunit/issues?q=is%3Aissue+project%3Anunit%2Fnunit%2F1+