bug#18247: Cyclic dependencies in (gnu package *) modules

[Ludovic Courtès]

address@hidden skribis:

> I'm currently unable to compile guix from git, with error messages that
> suggest cyclic dependencies between the modules.

Indeed.  That is fixed by reverting c5d8376.  Can you confirm?

> I just computed the strongly connected components of the (gnu package
> *) modules.  The non-trivial ones are listed below.
>
> There are three cycles of size 2:
>
> ((gnu packages emacs)  (gnu packages version-control))
> ((gnu packages flex)   (gnu packages bison))
> ((gnu packages python) (gnu packages zip))
>
> And one large strongly-connected component containing 51 modules:

Ouch.

Well, that is not really a problem per se.  The real problem is when
top-level bindings refer to each other, of course.

But anyway, I agree we need tooling or something to help deal with this
kind of issues.  Perhaps something like the script you posted, but that
would look at the set of bindings referenced from the top-level of a
module?  Or can we do better?

If Guile supported phases, such circular references would not be a
problem since it would not have to evaluate all of the imported modules
at expansion phase, just the ‘define-module’ clause.

Thanks,
Ludo’.