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From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: (guix modules) and =?utf-8?Q?=E2=80=98source-module-closure?=
	=?utf-8?Q?=E2=80=99?=
Date: Mon, 05 Sep 2016 00:24:41 +0200
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To: guix-devel <guix-devel@gnu.org>

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 =E2=80=98with-imported-modules=E2=80=99 usage, =
as explained
in the manual:

--8<---------------cut here---------------start------------->8---
   Usually you want the _closure_ of the module to be imported=E2=80=94i.e.=
, the
module itself and all the modules it depends on=E2=80=94rather than just the
module; failing to do that, attempts to use the module will fail because
of missing dependent modules.  The =E2=80=98source-module-closure=E2=80=99 =
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=3D239c6e276214813f59=
f761c9dc5cc0e9d266b49b

Comments welcome!

Ludo=E2=80=99.