From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ricardo Wurmus <ricardo.wurmus@mdc-berlin.de>
Subject: Re: (guix modules) and =?utf-8?Q?=E2=80=98source-module-closure?=
	=?utf-8?Q?=E2=80=99?=
Date: Mon, 5 Sep 2016 10:13:27 +0200
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To: Ludovic =?utf-8?Q?Court=C3=A8s?= <ludo@gnu.org>
Cc: guix-devel <guix-devel@gnu.org>


Ludovic Court=C3=A8s <ludo@gnu.org> writes:

> 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 usa=
ge, as explained
> in the manual:
>
> --8<---------------cut here---------------start------------->8---
>    Usually you want the _closure_ of the module to be imported=E2=80=94=
i.e., the
> module itself and all the modules it depends on=E2=80=94rather than jus=
t the
> module; failing to do that, attempts to use the module will fail becaus=
e
> 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=3D239c6e27621481=
3f59f761c9dc5cc0e9d266b49b

Ah, very nice!

Why is it necessary to read the file and parse the define-module
expression?  Does Guile not keep any of this information?  Should it?
Will something like this become part of Guile eventually?

~~ Ricardo