Re: Functional package interface

[spacecadet <spacecadet@purge.sh>]

> In the code there, the function propagate-packages will indeed try and
> propagate every package through the graph node.

I looked at your code, it's comprehensive. I wasn't sure such a thing
was possible with input rewriting, although I think there's still a lot
of benefit to the functional approach, like this:
> - some packages are present under different names (emacs has
> emacs-minimal, emacs, emacs-pgtk, emacs-wide-int...) and that is not
> handled by this function.

It should handle it pretty elegantly, since those packages inherit from
emacs, if you replace emacs they'll inherit from your replacement while
keeping their unique traits.

> - propagating some packages that are used in build-systems will trigger
> massive rebuilds (e.g. go, emacs, python, ocaml, texlive), you'll
> probably have to be smart about what you want to avoid to propagate, but
> it's great because guix can already hide a package to
> package-inputs-rewriting using (hidden-package {package-name}). There are some
> examples in the series.

No idea how, but I guess I should implement a #:mask-hidden? argument
to handle this. I have more basic issues for now, but that's a good
point.

> - this has a cost. I haven't timed it yet, but the slowdown is
>    noticeable, though still quite usable.

I'm doing a couple stupid things, it's improved with the last few
commits, but there's still a long way to go. If there's a cost to
syntax rule abuse, you were probably feeling that.

> - you of course have to get the packages into the function from a
>    profile. Here's it's done in RDE's code, but that should be quite
>    doable in Guix too.

Yeah, the implementation model is kinda strange. Having to put extra
code in every single module in the entire repo isn't a great
prerequisite for anything. It could be the point that prevents this
from manifesting. The mile long butt-ugly list of inputs that it needs
doesn't help.

Thanks for the tips. Work is still ongoing, but recursive propagation
now works when giving one package-set another as an input, so the
intended use-case is now possible.

- sc