Cancelling built-ins

[evanrittenhouse]

Feature description

Hi there! I'm currently using brush at $DAYJOB. One of the use cases that we need to support is remote timeout registration. I currently have this mostly working for external commands as we can just killpg the entire process group.

Use case / motivation

I'd like to cancel the running commands without killing the server process. That means that I can't use typical PID/PGID-level kill signals

Proposed solution

Currently, the best approach I have is to check for pending signals in applicable Execute::execute calls (or equivalently, check that a deadline has elapsed). That can be Rust-ified with a wrapper method or something as well. Spawning everything in subprocesses won't work as we have to preserve environment changes in the parent shell.

Additional context

In general, I'm wondering if there's been any thought put into how to best propagate cancellation through Brush (e.g. shell built-ins, spawned subprocess, commands running in Tokio tasks, etc.). I definitely could be missing something as I'm pretty new to shells in general. I'm happy to raise a PR to upstream this once I'm done as well, if that'd be helpful!

[reubeno]

Hi @evanrittenhouse -- thanks for reaching out! There are good questions in here.

I have a few clarifying questions to better understand your use case. Could you explain a bit more what you mean by server process? Also, in your use case are you launching brush as an executable or embedding its libraries in your executable? Do you have control over the scripts being execute / commands being run to inject wrappers that implement timeouts, or are you looking to do this at a lower level?

(Perhaps a concrete example or two might help? (They can be fictional or contrived).)

One way or the other, I think there's good opportunity to do something useful here--and we'd always love to see contributions 😄.

[oech3]

env true --version disables built-in true.

[oech3]

Just adding aliases to profile?

[reubeno]

@oech3 I don't think this conversation is around disabling builtins -- it's around cancelling the execution of a running builtins mid-flight.

[oech3]

Is this issue about Ctrl+C? I think shadowing is still valid workaround for the case because it is replaced by external process.