Edouard Klein writes:

> Dear Guixers,
>
> I recently broke jupyter while updating python-prompt-toolkit (a mistake
> I'm still trying to fix...) despite doing my best to follow the
> instructions of the manual:
> https://guix.gnu.org/manual/en/html_node/Packaging-Guidelines.html
> https://guix.gnu.org/manual/en/html_node/Submitting-Patches.html#Submitting-Patches
>
> Because of the subtle consequences of editing a package are hard to keep
> track of, I wrote the attached script (you need sharness to run it, but
> with slight modification it can become a standalone script).
>
> This script goes beyond the instructions of the manual on two fronts:
> - First, it not only tries to build the packages, but also to install
> them,
> - Secondly, it does not limit itself to the dependents (as listed by
> guix refresh --list-dependents) of the packages one is meddling with,
> but to the whole reverse bags (as listed by guix graph
> --type=reverse-bag).
>
> Both these extensions are necessary to discover that my update broke the
> jupyter package:
> - jupyter builds, so if you don't try to install it you won't discover
> it's broken
> - the leafs of the dependency graph that depend on jupyter fail to build
> for reasons unrelated to python-prompt-toolkit, so by just building the
> leafs (which are what is being returned by guix refresh
> --list-dependents) you can't discover jupyter's broken status.
>
> I think an update of the manual is in order (I've added it to my own
> TODO queue, but I have no idea when I'll be able to get to it) but I
> first wanted to share my script in case it may be useful to someone
> else, and gather some feedback as to whether other developers have
> encountered these kind of errors, and the way seasoned developers make
> sure they don't push breaking changes.
>
> Cheers,
>
> Edouard.