Change wait_with_output to borrow instead of taking ownership

[Binlogo]

Context & Motivation

To implement the timeout feature for the xshell crate, as discussed in this pull request, the child process will use wait_with_output until the timeout occurs, at which point it will be terminated.

        let out_res = if let Some(timeout) = self.data.timeout {
            let (tx, rx) = mpsc::channel();
            let handle = thread::spawn(move || {
                let output = child.wait_with_output();
                let _ = tx.send(output);
            });
            handle.join().unwrap();
            match rx.recv_timeout(timeout) {
                Ok(output) => output,
                Err(err) => {
                    // FIXME: Kill the child, borrow of moved value: `child`
                    // child.kill();
                    return Err(Error::new_timeout(self, err));
                }
            }
        } else {
            child.wait_with_output()
        };

Since .wait_with_output need the child's ownership, when spawned, I can't use it to call .kill anymore. I tried Arc way, but it still failed:

error[E0507]: cannot move out of dereference of MutexGuard<'_, Child>

It appears that both wait and try_wait only require borrowing &mut self. We could consider refactoring wait_with_output to require borrowing instead of taking ownership.

Breaking change?

This is my first time submitting a PR to the Rust standard library. It appears this change could be breaking. I'm unsure if we can refactor this method in this manner. If any additional actions are required, I will follow through.

r? @matklad

[rustbot]

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[matklad]

std::Process is a stable API, so we can't change it at all.

What we could potentially do is to add a new API which allows this use-case (concurrently reading process output and killing it), but that needs to go through the standard process with API change proposal:

https://std-dev-guide.rust-lang.org/development/feature-lifecycle.html

I personally don't know what would be the right shape for a new API here, or whether the new API is warranted (the user-code can "just" re-implement its own wait_with_output, though that requires re-impelmenting the read2 utility) .

[Binlogo]

std::Process is a stable API, so we can't change it at all.

What we could potentially do is to add a new API which allows this use-case (concurrently reading process output and killing it), but that needs to go through the standard process with API change proposal:

https://std-dev-guide.rust-lang.org/development/feature-lifecycle.html

I personally don't know what would be the right shape for a new API here, or whether the new API is warranted (the user-code can "just" re-implement its own wait_with_output, though that requires re-impelmenting the read2 utility) .

Oh, making a change like this seems challenging. Thank you for your advice and guidance. Proposing a new API appears to be a lengthy process, yet I view it as an opportunity to learn and grow within the Rust community. I'll take some time to delve into it.