`From<PipeReader> for File` and `From<PipeWriter> for File`

[Scripter17]

Proposal

Problem statement

The soon to be stable PipeReader and PipeWriter can be turned into Files by going through OwnedFd, but File doesn't implement From for either. I think it's simple, small, and common enough to warrant the two implementations.

Motivating examples or use cases

I was looking for a way to stream text output from a std::thread::scope in a Rocket endpoint as a response. From what little I can figure out from stumbling around, the anonymous pipe API seems like an okay way of handling this. Even if it's not ideal (I'll see if I can get the actual Stream stuff working), I argue the implementations should still be implemented for anyone using APIs that require specifically File.

Solution sketch

impl From<PipeReader> for File {
    impl from(value: PipeReader) -> Self {
        OwnedFd::from(value).into()
    }
}

impl From<PipeWtriter> for File {
    impl from(value: PipeReader) -> Self {
        OwnedFd::from(value).into()
    }
}

Alternatives

Links and related work

What happens now?

This issue contains an API change proposal (or ACP) and is part of the libs-api team feature lifecycle. Once this issue is filed, the libs-api team will review open proposals as capability becomes available. Current response times do not have a clear estimate, but may be up to several months.

Possible responses

The libs team may respond in various different ways. First, the team will consider the problem (this doesn't require any concrete solution or alternatives to have been proposed):

• We think this problem seems worth solving, and the standard library might be the right place to solve it.
• We think that this probably doesn't belong in the standard library.

Second, if there's a concrete solution:

• We think this specific solution looks roughly right, approved, you or someone else should implement this. (Further review will still happen on the subsequent implementation PR.)
• We're not sure this is the right solution, and the alternatives or other materials don't give us enough information to be sure about that. Here are some questions we have that aren't answered, or rough ideas about alternatives we'd want to see discussed.