wasi-common: cannot use file handles for `WasiCtxBuilder::std[in|out|err]`

[peterhuene]

It appears that #1561 regressed WasiCtxBuilder::stdin, WasiCtxBuilder::stdout, and WasiCtxBuilder::stderr because it is using OsOther which will error with invalid argument when given a file handle.

cc @kubkon.

This caused a CI failure in the .NET implementation that I hadn't had time to look into the last few days.

Unfortunately, there's a test coverage hole in Wasmtime CI where only a pipe handle was used for these functions, which is why the regression wasn't caught (OsOther works fine for pipes).

[kubkon]

Oh shoot, it seems that my refactoring regressed a lot more than expected, sorry about that! I’ll have a look ASAP and also will try figure out an additional test. Thanks for the report @peterhuene!

[kubkon]

Just out of curiosity, would #1600 fix this issue for you?

[peterhuene]

From a quick glance, I don't think it would, as the .NET API goes through the WASI C API, which remains using OsOther.

I was thinking of a more specific fix to where we currently handle PendingEntry::OsHandle to support either a file handle or an other handle, ala peterhuene@21b0d6e. It does incur an extra stat to see what type of handle it is, though.

[peterhuene]

Breaking change to the Rust API aside, I think if we changed those to OsFile, your approach would work. The C API is only accepting paths to files.

[kubkon]

Since #1600 landed, I’m closing this one. Feel free to reopen it though if you feel it’s not been fully fixed @peterhuene!