From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?utf-8?Q?Ludovic_Court=C3=A8s?= <ludo@gnu.org>
Subject: Re: Store channel specification in profile
Date: Mon, 24 Feb 2020 17:16:25 +0100
Message-ID: <87ftf0j6zq.fsf@gnu.org>
References: <87blsyelgm.fsf@ambrevar.xyz> <m1h82q8ub3.fsf@khs-macbook.home>
 <87tv69bezo.fsf@gnu.org> <87zhg1xvmo.fsf@ambrevar.xyz>
 <CAJ3okZ2-Lniaw8ARXre7atDyHmWEeHwm25CkpbSdSk9un4r4OQ@mail.gmail.com>
 <874kx8gxh1.fsf@ambrevar.xyz>
 <CAJ3okZ0GGJAJ_YRSdm4we-YYwUTzi85RvJkMHnPkSzVjVxPWSw@mail.gmail.com>
 <87blreasgd.fsf@ambrevar.xyz> <87pnfpsgfx.fsf@gnu.org>
 <CAJ3okZ29N2B+ikwupN4cevzvZHpz0CK31tXoZcp50aPCtHKFAQ@mail.gmail.com>
 <87a76rqu5j.fsf@ambrevar.xyz>
 <CAJ3okZ1KWzjThKh2QF7RGBJuX+63QpY822NF6fuX9FkgddLRnw@mail.gmail.com>
 <877e1vqowd.fsf@ambrevar.xyz> <87zhe4px2a.fsf@ambrevar.xyz>
 <87wo91p9yt.fsf@gnu.org> <87eev8gewx.fsf@ambrevar.xyz>
 <87pneq140d.fsf@gnu.org> <8736bldmzr.fsf@ambrevar.xyz>
 <87zhdp2p16.fsf@gnu.org> <87imkdky1w.fsf@ambrevar.xyz>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Return-path: <guix-devel-bounces+gcggd-guix-devel=m.gmane-mx.org@gnu.org>
Received: from eggs.gnu.org ([2001:470:142:3::10]:39060)
 by lists.gnu.org with esmtp (Exim 4.90_1)
 (envelope-from <ludo@gnu.org>) id 1j6GPH-0002I7-E4
 for guix-devel@gnu.org; Mon, 24 Feb 2020 11:16:32 -0500
In-Reply-To: <87imkdky1w.fsf@ambrevar.xyz> (Pierre Neidhardt's message of
 "Tue, 11 Feb 2020 15:18:03 +0100")
List-Id: "Development of GNU Guix and the GNU System distribution."
 <guix-devel.gnu.org>
List-Unsubscribe: <https://lists.gnu.org/mailman/options/guix-devel>,
 <mailto:guix-devel-request@gnu.org?subject=unsubscribe>
List-Archive: <https://lists.gnu.org/archive/html/guix-devel>
List-Post: <mailto:guix-devel@gnu.org>
List-Help: <mailto:guix-devel-request@gnu.org?subject=help>
List-Subscribe: <https://lists.gnu.org/mailman/listinfo/guix-devel>,
 <mailto:guix-devel-request@gnu.org?subject=subscribe>
Errors-To: guix-devel-bounces+gcggd-guix-devel=m.gmane-mx.org@gnu.org
Sender: "Guix-devel"
 <guix-devel-bounces+gcggd-guix-devel=m.gmane-mx.org@gnu.org>
To: Pierre Neidhardt <mail@ambrevar.xyz>
Cc: Guix Devel <guix-devel@gnu.org>

Hi Pierre,

Pierre Neidhardt <mail@ambrevar.xyz> skribis:

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

[...]

>> What we lack is the ability to obtain a =E2=80=9Cmanifest.scm=E2=80=9D k=
ind of file
>> (code) that users can pick as a starting point in their migration
>> towards declarative deployment.
>
> You mean a script like the following?
>
> ;; Run with:
> ;;     guile -s FILE ~/.guix-profile
>
> (use-modules (guix profiles)
>              (gnu packages)             ; fold-packages
>              (guix packages)            ; package structure
>              (ice-9 match)
>              (ice-9 pretty-print))
>
>
> (define (packages-by-name name)
>   (fold-packages (lambda (package list)
>                    (if (string=3D? (package-name package) name)
>                        (cons package list)
>                        list))
>                  '()))
>
> (define (guix-manifest where)
>   (sort (map (lambda (entry)
>                (let* ((name (manifest-entry-name entry))
>                       (out (manifest-entry-output entry))
>                       (version (manifest-entry-version entry))
>                       (default-version (match (packages-by-name name)
>                                          ((first-name . rest)
>                                           (package-version
>                                            first-name))
>                                          (else #f))))
>                  (string-append name
>                                 (if (and default-version
>                                          (not (string=3D version default-=
version)))
>                                     (format #f "@~a" version)
>                                     "")
>                                 (if (string=3D out "out")
>                                     ""
>                                     (format #f ":~a" out)))))
>              (manifest-entries (profile-manifest where)))
>         string<?))

Yes!  That alone would already be a useful tool to migrate from the
=E2=80=9Cimperative=E2=80=9D style to the declarative style.  I=E2=80=99m s=
ure it=E2=80=99d be good
enough 90% of the time.

(Note: we should remove the =E2=80=98sort=E2=80=99 call here as the order o=
f packages in
the manifest is significant when there are file collisions.)

How does that sound?  Would you like to integrate something like this,
maybe =E2=80=98guix package --export=E2=80=99 or something?

> ;; Thanks to Ivan Vilata-i-Balaguer for this:
> (define (guix-commit)
>   (let ((guix-manifest (profile-manifest (string-append (getenv "HOME") "=
/.config/guix/current"))))
>     (match (assq 'source (manifest-entry-properties (car (manifest-entrie=
s guix-manifest))))
>       (('source ('repository ('version 0) _ _
>                              ('commit commit) _ ...))
>        commit)
>       (_ #f))))
>
> (match (command-line)
>   ((_ where)
>    (format #t ";; commit: ~a\n" (guix-commit))
>    (pretty-print
>     `(specifications->manifest
>       ',(guix-manifest where))))

Emitting channel info as comments like this, and/or a warning when
there=E2=80=99s a conflict (packages coming from different commits of the s=
ame
channel) could be done as a second step.

Thanks,
Ludo=E2=80=99.