Re: Minimal working examples of packages for experimentation?

[Jelle Licht <jlicht@fsfe.org>]

Hello Rodrigo!

Rodrigo Morales <moralesrodrigo1100@gmail.com> writes:

> [snip]

>   The following is the package that I wrote.
>
>   ,----
>   | (define-module (my-simple)
>   |   #:use-module (guix licenses)
>   |   #:use-module (guix packages)
>   |   #:use-module (guix gexp)
>   |   #:use-module (guix build-system trivial)
>   |   #:use-module (guix download))
>   |
>   | (define-public my-simple-1
>   |   (package
>   |    (name "my-simple-1")
>   |    (version "2.10")
>   |    (source (origin
>   |             (method url-fetch)
>   |             (uri "
> https://www.gnu.org/graphics/heckert_gnu.transp.small.png")
>   |             (sha256 (base32
> "1686w7x3qk85i5693nrj7lbdh64232fdsqd5rgxgijv1y39rldbr"))))
>   |    (build-system trivial-build-system)
>   |    (synopsis "My synopsis")
>   |    (description "My description")
>   |    (home-page "https://example.org/")
>   |    (license gpl3+)))
>   `----

> [snip]

> 3 What I'm looking for
> ======================
>
>   1. Why the package that I wrote failing? How could I fix it?

Looking at `info "(guix) Build Systems"'[0], in the blurb about the
trivial-build-system:

--8<---------------cut here---------------start------------->8---
     This build system requires a ‘#:builder’ argument.  This argument
     must be a Scheme expression that builds the package output(s)—as
     with ‘build-expression->derivation’ (*note
     ‘build-expression->derivation’: Derivations.).
--8<---------------cut here---------------end--------------->8---

The reason your package fails to build, is that it doesn't provide such
a #:builder argument. This argument is also responsible for creating the
actual output, which can be a file or directory.

The simplest snippet I can think of for making your package "work":

--8<---------------cut here---------------start------------->8---
(define-public my-simple-1
  (package
    ; .. existing stuff
    (arguments (list #:builder #~(mkdir #$output)))))
--8<---------------cut here---------------end--------------->8---

Note that this simply creates the output directory, and does nothing
else.

What may seem a bit misleading here is that "build expressions" have
mostly been ported to this hip thing called G-Expressions (see `info
"(guix) G-Expressions"' [1]).

>   2. Do you know simpler package definitions (aka minimal working
>      examples) that I could use for experimenting?

Simple does not always imply easy. If we're talking about an easy to use
build system, I think the `copy-build-system' could work, as does the
gnu-build-system as it allows you to play with the moving parts without
having to supply all of these moving parts yourself :).

A package that uses the trivial-build-system that does slightly more is
`inxi-minimal', which you can find by issuing a `guix edit inxi-minimal'.

HTH!
 - Jelle

[0]: https://guix.gnu.org/manual/devel/en/html_node/Build-Systems.html#index-trivial_002dbuild_002dsystem
[1]: https://guix.gnu.org/manual/devel/en/html_node/G_002dExpressions.html