Inheriting raw file descriptors when building a context

[jedisct1]

Right now, when building a new WasiCtx, we can inherit stdin/stdout/stderr or preopened directories.

But would it be acceptable to also provide a way to map a Wasi file descriptor to a RawFd?

[sunfishcode]

One way to do this would be to add a way to preopen individual files -- https://github.com/WebAssembly/WASI/issues/91 -- so that we can tell applications about the file descriptors we're sending them. Otherwise, applications wouldn't know what to do with the extra file descriptors they're given unless they have some special arrangement with the host environment.

[pchickey]

Closing this as not planned - As Dan said 6.5 years ago, this could require significant changes to the WASI filesystem standard or at least a pretty different implementation than wasmtime-wasi provides at the moment. If someone wants to freshly engage with those projects and has a compelling concrete use case it enables for wasmtime's users, please open a new issue.