(guix modules) and ‘source-module-closure’

[ludo@gnu.org (Ludovic Courtès)]

Hi!

Commit 7ca87354db53fd1e1a7a3dfeddb9a598ea064bbe adds (guix module),
which provides a way to compute the closure of a Scheme module by
looking at its source code.

This has to do with typical ‘with-imported-modules’ usage, as explained
in the manual:

--8<---------------cut here---------------start------------->8---
   Usually you want the _closure_ of the module to be imported—i.e., the
module itself and all the modules it depends on—rather than just the
module; failing to do that, attempts to use the module will fail because
of missing dependent modules.  The ‘source-module-closure’ procedure
computes the closure of a module by looking at its source file headers,
which comes in handy in this case:

     (use-modules (guix modules))   ;for 'source-module-closure'

     (with-imported-modules (source-module-closure
                              '((guix build utils)
                                (gnu build vm)))
       (gexp->derivation "something-with-vms"
                         #~(begin
                             (use-modules (guix build utils)
                                          (gnu build vm))
                             ...)))
--8<---------------cut here---------------end--------------->8---

The benefit can be seen in the next commit:

  http://git.savannah.gnu.org/cgit/guix.git/commit/?id=239c6e276214813f59f761c9dc5cc0e9d266b49b

Comments welcome!

Ludo’.