BetterReader.read_with_cancel() returns both the read promise, and a
function that can be used to cancel the read. A cancelled read is
placed back into the BetterReader's chunk buffer, to be consumed by the
next user that requests a read.
This is used by Coupler so that when the coupler is closed, its pending
read() call does not consume the next batch of input.
This fixes the problem we were having with child applications consuming
one chunk of stdin after they are closed, meaning the first key you
press after an app exits would disappear.
Co-authored-by: KernelDeimos <eric.alex.dube@gmail.com>
After launching an app, if successful, we connect stdio streams to it,
and wait for it to exit before we return to the prompt.
stdio is implemented as regular AppConnection messages:
- stdin: `{ $: 'stdin', data: Uint8Array }` from phoenix -> child
- stdout: `{ $: 'stdout', data: Uint8Array }` from child -> phoenix
Terminal and Phoenix now communicate with each other using the same
style, instead of 'input' and 'output' messages. This will help with
eventually running subshells.
SIGINT currently is not sent. We also suffer from the same "one more
read from stdin happens after app exits" bug that's in
PathCommandProvider where I copied the stdin code from.
