Re: Proposal: prefetch tarballs in a batch

[Ludovic Courtès]

Nikita Karetnikov <address@hidden> skribis:

> 1. ‘guix prefetch’ tries to configure and build some packages instead of
>    just downloading them.  I tried the following on a machine with the
>    empty store:
>
>    a. Ran ‘guix prefetch hello’.  Some packages were downloaded and
>       built (I gathered those are needed to download the other packages,
>       so I didn’t write down the names.  If I recall correctly, Guile
>       was in that list.)

Yes, by default ‘guile-final’ is used to build derivations (including
download derivations), so that needs to be built before anything else
can be done.  (And that involves building gcc, libc, etc. first.)

>    b. Invoked ‘guix build hello’ without network access.  The command
>       succeeded.  No questions here.
>
>    c. Called ‘guix prefetch emacs’.  These packages were configured and
>       built: pkg-config, libunistring, ncurses, libatomic_ops, patch,
>       tar, xz, gzip, zlib, which, gc, perl, m4, readline, libffi,
>       texinfo, libtool, gmp, libtasn1, nettle, guile, gnutls.
>
>       Are these essential, or is there an error in ‘guix prefetch’?
>       According to the build logs, the install prefix of gmp is
>       ‘/gnu/store/hpaz49xz76p4qmpjc9r33hni1w781y66-gmp-5.1.3’, which
>       doesn’t appear in the lists provided by ‘guix prefetch hello’ and
>       ‘guix prefetch emacs’.  I’m not sure why it’s the case.

Perhaps these were just the prerequisites for ‘guile-final’ no?

> 2. I think it would be nice to output the location of a tarball after
>    running ‘guix prefetch’, but I’m not sure how to get the relevant
>    derivation.  For ‘hello’, it’s neither
>
>      (package-source-derivation store (package-source hello))
>
>    nor
>
>      (package-derivation store hello)
>
>    because the derivation listed in the initial output of ‘guix prefetch
>    hello’ differs.  Of course, it’s possible to filter the list
>    produced by
>
>      (build-derivations
>       store
>       (map (lambda (drv)
>              ;; (format #t "   ~a~%" (derivation-file-name drv))
>              (format #t "   ~a~%" drv)
>              drv)
>            (derivations-to-prefetch
>             store
>             (package-derivation store package)))))
>
>    But it’s error-prone, so I’d rather avoid that.

I don’t understand.  You can do:

--8<---------------cut here---------------start------------->8---
scheme@(guile-user)> (derivation->output-path
                       (package-source-derivation s (package-source hello)))
$4 = "/gnu/store/070fnjll8hb3q2l4373bbahh2i1n2qhg-hello-2.9.tar.gz"
--8<---------------cut here---------------end--------------->8---

Isn’t it what you want?

> 3. I’m planning to add ‘--dry-run’, which will simply print the list of
>    needed derivations.

I think this should use ‘show-what-to-build’, as in ‘guix build’ and
other commands, so that it would also show what other derivations need
to be built, such as those for ‘guile-final’.

> What options would you like to see implemented?

Probably all of ‘%standard-build-options’ from (guix scripts build) can
be made available?

Thanks for the nice work!

Ludo’.