Re: Adding plumbing subcommand 'derivation'?

[Simon Tournier]

Hi,

On ven., 19 avril 2024 at 16:02, Ludovic Courtès <ludo@gnu.org> wrote:

> We should see how that fits into the set of tools we already have, in
> particular the (guix derivations) interface and the REPL meta-commands.
>
> My gut feeling, with a Schemer bias, is that we’d rather enrich the
> Scheme API and/or REPL than add more commands (this is not Nix :-)).
>
> But I don’t know, maybe we can have both?

Yes, I think that’s orthogonal and a good idea.

Maybe a new plumbing generic subcommand, as “guix inspect” or “guix
store”, where showing the fields of a derivation would be a
sub-subcommand.  For instance, diffing two derivations from the
command-line seems helpful when  debugging – I often do that with Emacs
exploiting buffer facilities. :-)

In addition, it could be helpful to improve the readability for the
pretty-printer.  Other said, somehow redesign this:

--8<---------------cut here---------------start------------->8---
(set-record-type-printer! <derivation>
                          (lambda (drv port)
                            (format port "#<derivation ~a => ~a ~a>"
                                    (derivation-file-name drv)
                                    (string-join
                                     (map (match-lambda
                                           ((_ . output)
                                            (derivation-output-path output)))
                                          (derivation-outputs drv)))
                                    (number->string (object-address drv) 16))))
--8<---------------cut here---------------end--------------->8---

It looks like a plan. ;-)

Cheers,
simon