Hi Pierre,

"Pierre-Henry F." <contact@phfrohring.com> writes:

> So, we have, in ~bash~:
>
>   $ lzip --decompress release_3.tar.lz
>   $ tar xf release_3.tar
>   $ cd blog/ # coming from the preceding line.
>   $ tree
>   .
>   ├── bin
>   │   └── program
>   └── src
>       └── hello_world.py
>
>   $ cat src/hello_world.py
>   print("Hello world!")
>
>   $ cat bin/program
>   #! /usr/bin/env bash
>
>   script_path="${BASH_SOURCE[0]}"
>   script_dir="$(dirname $script_path)"
>   python3 "$script_dir/../src/hello_world.py"
>
> That's it.
>
> The idea is to build a Guix package that does exactly that.
> Expected outcome:
>
>   $ guix package -s blog
>   # fetch release_3.tar.lz
>   # uncompress ...
>   # ...
>
>   $ program
>   Hello World!
>
>
> My question: how to build that Guix package?  I try to get something working using
> the docs.  This is how the package looks to far:
>
>   (use-modules
>     (guix packages)
>     (guix download)
>     (guix build-system trivial)
>     (guix licenses)
>     (guix gexp)
>     (gnu packages base)
>     (gnu packages python))
>
>
>   ;; The "derivation" i.e. low level sequence of instructions that the build deamon is
>   ;; supposed to execute on the behalf of the user.
>   (define build-drv
>     (gexp->derivation
>       "the-thing"
>       #~(begin
>           (mkdir #$output)
>           (chdir #$output)
>           (symlink (string-append #$coreutils "/bin/ls")
>             "list-files"))))
>
>
>   (package
>     (name "blog")
>     (version "3")
>     (source
>       (origin
>         (method url-fetch)
>         (uri (string-append "/home/phf/programs/blog/releases/release_" version ".tar.lz"))
>         (sha256
>           (base32
>             "1y819b53ksyas6asldysr0r8p73n5i8ipbpmbgjrfx8qz8cy2zsx"))))
>     (build-system trivial-build-system)
>     (arguments `(#:builder ,build-drv))
>
>     (inputs `(("python" ,python)))
>     (synopsis "Guix 'hello world' to learn about Guix")
>     (description "Guess what GNU Hello prints!")
>     (home-page "http://www.gnu.org/software/hello/")
>     (license gpl3+))
>
> Assuming everything else is correct, would you please help refine ~build-drv~ until
> it matches the ~bash~ above ?
>
> This is what the execution trace looks like:
>
>   phf@f02c:~/tools/guix/packages$ guix build --keep-failed --verbosity=2 --file=./blog.scm
>   substitute: updating substitutes from 'https://ci.guix.gnu.org'... 100.0%
>   building /gnu/store/8b0gyazhgmc9rkrxir7vxpav0x28xk3d-blog-3.drv...
>   ERROR: In procedure primitive-load:
>   In procedure scm_lreadr: /gnu/store/zlbf2x6n4084v0cpw2rh9dydqmi5b2rn-blog-3-guile-builder:1:10: Unknown # object: #\<

This error is because you can’t pass a derivation object as the
“#:builder” argument.  It has to be some quoted Scheme code that can run
in the build environment.

I took a little time and wrote a package definition that matches your
example.  There are some things you could do to change your source code
to make it more in-line with what Guix expects, but I didn’t do that.  I
hope that an example dealing with what you have will be more helpful.

I’ve attached the package definition I came up with (note that I changed
the URL of the tarball).