How do you debug build-side code?

["David Arroyo" <david@aqwari.net>]

Hello,

I currently use Guix on a foreign distro to define development and build environments. I'm trying to extend guix with types that build an s6[1] supervision tree in the store from a declarative definition. I can then use that to build a guix profile (or a pack) with everything needed for s6-svscan to run and supervise these services.

This is my current attempt:

https://git.sr.ht/~droyo/guix-channel/tree/1ca4a1043c1f38bcc118046fa5ba771cf47393a9/item/aqwari/services/s6.scm
https://git.sr.ht/~droyo/guix-channel/tree/1ca4a1043c1f38bcc118046fa5ba771cf47393a9/item/example/router.scm

However, `guix build -f router.scm` currently fails. The specific error is something about incorrect arguments to "apply". I'm sure I can find it eventually, but this is just one of many errors I've made, and I've had a bear of a time fixing them. I feel like I am in uncharted territory, because the docs I can find all talk about packages, and I'm not trying to build a package. Often the stack traced I get do not include my code at all, so it's hard to tell where my mistake is.

I'd love to hear how others debug errors in the build-side code. Is there any way for me to trace the function calls or even have an interactive debugging session?

David

[1]: https://skarnet.org/software/s6/index.html