stdout, stderr not interleaving correctly

[heaths]

Writes to the piped stdout and stderr are not interleaving correctly. Maybe need to join the streams but then how do we differentiate what should be written to stdout vs. stderr?

cargo run --example=printenv

Prints to stdout or stderr for every other line. Happens to be alphabetical in bash on ubuntu-22.04.

cargo run -- run -- cargo run --example=printenv

Prints lines in a random order. I was hoping that each of stdout and stderr would buffer - and perhaps they are - but the futures are completed non-chronologically. Will need to rethink how to handle this. Likely not async, which means back to the old LineWriter idea.

[heaths]

Looks like we can redirect to a Writer: https://doc.rust-lang.org/nightly/std/process/struct.Stdio.html#method.from-5. Using this, we can use an MPSC or, perhaps, directly write into a queue from which another thread will dequeue sequentially.

[heaths]

Seems it's impossible to pass your own Writer to Child::stdout() because of limited implementations of Into<Stdio>. But there are some ideas in tokio-rs/tokio#1386.

[heaths]

To do this best - like Go's os/exec package - we may need to create a PTY. See #29. For now, the best we can probably do here is to queue writes as fast as possible to a buffered channel and process each line in sequence much like locking a terminal buffer would do. It gets us closes within async limits.