Subject: Re: [PATCH 1/2] build-system: mix: Allow loading Erlang dependencies in Mix driven builds.

From: Liliana Marie Prikler <[email-masked]>
Date: Wed, 25 Sep 2024 20:42:47 +0200

Am Mittwoch, dem 25.09.2024 um 10:24 +0200 schrieb Giacomo Leidi:
> Fixes <https://issues.guix.gnu.org/73453>
Note: It's not official yet, but Fixes: <URL> is nice for a trailer. 
If it fits into 80 columns, you can also do Fixes: [shortdoc] <URL>.

> * guix/build/mix-build-system.scm (elixir-relative-libdir): New
> variable;
> (elixir-libdir): call elixir-relative-libdir;
Use full sentences, end each with a period (dot).
> (set-erl-env): this new phase sets ERL_LIBS to allow Erlang's virtual
> machine to load Erlang dependencies in Mix builds, in addition to
> Elixir
> ones;
> (%standard-phases): add set-erl-env phases.
> 
> Change-Id: Ic1ef5db20680bfd265fbac72bafb760d21135f68
> ---
>  guix/build/mix-build-system.scm | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/guix/build/mix-build-system.scm b/guix/build/mix-build-
> system.scm
> index 0b021da791..41f6061444 100644
> --- a/guix/build/mix-build-system.scm
> +++ b/guix/build/mix-build-system.scm
> @@ -1,6 +1,7 @@
>  ;;; GNU Guix --- Functional package management for GNU
>  ;;; Copyright © 2023 Pierre-Henry Fröhring <[email-masked]>
>  ;;; Copyright © 2024 Igor Goryachev <[email-masked]>
> +;;; Copyright © 2024 Giacomo Leidi <[email-masked]>
>  ;;;
>  ;;; This file is part of GNU Guix.
>  ;;;
> @@ -39,10 +40,15 @@ (define-module (guix build mix-build-system)
>  ;; minor version number of the Elixir used in the build.
>  (define %elixir-version (make-parameter "X.Y"))
>  
> +(define (elixir-relative-libdir version)
> +  "Return the relative path inside a package namespace in the store
> where all
> +libraries for a specified Elixir VERSION are installed."
> +  (string-append "lib/elixir/" version))
> +
>  (define* (elixir-libdir path #:optional (version (%elixir-version)))
>    "Return the path where all libraries under PATH for a specified
> Elixir
>  VERSION are installed."
> -  (string-append path "/lib/elixir/" version))
> +  (string-append path "/" (elixir-relative-libdir version)))
Rather than having two procedures here, I think calling elixir-libdir
on "lib/erlang/lib" does what you want.

>  (define* (strip-prefix name #:optional (prefix "elixir-"))
>    "Return NAME without the prefix PREFIX."
> @@ -94,6 +100,17 @@ (define* (set-mix-env #:key inputs mix-path mix-
> exs #:allow-other-keys)
>    (setenv "MIX_PATH" (or mix-path ""))
>    (setenv "MIX_REBAR3" (string-append (assoc-ref inputs "rebar3")
> "/bin/rebar3")))
>  
> +(define* (set-erl-env #:key inputs #:allow-other-keys)
> +  "Add dependencies in Elixir's load path."
> +  (setenv "ERL_LIBS"
> +          (string-join (search-path-as-list
> +                        `("lib/erlang/lib"
> +                          ,(elixir-relative-libdir (elixir-version
> inputs)))
> +                        (map (match-lambda
> +                               ((label . package) package))
> +                             inputs))
> +                       ":")))
> +
>  (define* (set-elixir-version #:key inputs #:allow-other-keys)
>    "Store the version number of the Elixir input in a parameter."
>    (%elixir-version (elixir-version inputs))
> @@ -152,6 +169,7 @@ (define %standard-phases
>      (delete 'configure)
>      (add-after 'install-locale 'set-mix-env set-mix-env)
>      (add-after 'set-mix-env 'set-elixir-version set-elixir-version)
> +    (add-after 'set-elixir-version 'set-erl-env set-erl-env)
I think we can reorder this so that set-elixir-version is called first
and set-erl-env can be inlined into set-mix-env.

Cheers