[bug#66801] [PATCH v3 01/14] build-system: Add mix-build-system.

[Pierre-Henry Fröhring]

* WAITING Comment
** lilyp
> * guix/build-system/mix.scm,
> * guix/build/mix-build-system.scm: New modules.
Avoid spanning a change across multiple files.  Use
file: Change.
file2: Likewise.

>  gnu/packages/elixir.scm         |  62 ++++++++++-
>  guix/build-system/mix.scm       | 187
> ++++++++++++++++++++++++++++++++
>  guix/build/mix-build-system.scm | 171 +++++++++++++++++++++++++++++
You committed two changes at once here.  Split them.


** phf
How are changes counted? I've counted one because all of these changes
are needed
to introduce the ~mix-build-system~. Should it be:
#+begin_example
,* gnu/packages/elixir.scm (elixir): Search path GUIX_ELIXIR_LIBS added.
,* gnu/packages/elixir.scm (elixir): Wrap programs with
ERL_LIBS=${GUIX_ELIXIR_LIBS}.
,* guix/build-system/mix.scm: New modules.
,* guix/build/mix-build-system.scm: New modules.
#+end_example
or something else?


* WAITING Comment
** lilyp
> +(define* (set-mix-env #:key inputs mix-path mix-exs #:allow-other-
> keys)
> +  "Set environment variables.
> +See:
> https://hexdocs.pm/mix/1.15.7/Mix.html#module-environment-variables";
> +  (setenv "MIX_HOME" (getcwd))
> +  (setenv "MIX_ARCHIVES" "archives")
> +  (setenv "MIX_BUILD_ROOT" "_build")
> +  (setenv "MIX_DEPS_PATH" "deps")
> +  (setenv "MIX_PATH" (or mix-path ""))
> +  (setenv "MIX_REBAR3" (string-append (assoc-ref inputs "rebar3")
> "/bin/rebar3"))
> +  (setenv "MIX_EXS" mix-exs)
> +  (%elixir-version (elixir-version inputs)))
%elixir-version is not an environment variable.  You should set this up
separately or at the very least add a big fat comment explaining what
you're doing here :)


** phf
What about both?
#+begin_src scheme
(define* (set-elixir-version #:key inputs #:allow-other-keys)
  "Set Elixir version.
Compiled libraries are specific to each Elixir version. If a library is intended
to be used with multiple Elixir versions, it needs to be compiled separately for
each version. The parameter %elixir-version, set for the current build, is used
to differentiate between the compiled versions of libraries corresponding to
different Elixir versions."
  (%elixir-version (elixir-version inputs))
  (format #t "Elixir version: ~a~%" (%elixir-version)))
#+end_src


* WAITING Comment
** lilyp
> +     (list (search-path-specification
> +            (variable "GUIX_ERL_LIBS")
> +            (files (list "lib/erlang/lib"
> +                         (string-append "lib/elixir/" (version-
> major+minor version)))))))
I suppose ERL is for erlang?  What do we use for elixir then?


** phf
Changed for ~GUIX_ELIXIR_LIBS~. Is that OK?


* WAITING Comment
** lilyp
> +(define* (install-dependencies . _)
> +  "Install dependencies."
> +  (setenv "ERL_LIBS" (getenv "GUIX_ERL_LIBS")))
Why not do this as part of setting up mix-env?


** phf
If we have this phase in the ~elixir~ package:
#+begin_src scheme
(add-after 'install 'wrap-programs
            (lambda* (#:key inputs outputs #:allow-other-keys)
              (let* ((out (assoc-ref outputs "out"))
                     (programs '("elixir" "elixirc" "iex" "mix")))
                (for-each (lambda (program)
                            (wrap-program (string-append out "/bin/" program)
                              '("ERL_LIBS" prefix ("${GUIX_ELIXIR_LIBS}"))))
                          programs))))
#+end_src

and this native search path:
#+begin_src scheme
(search-path-specification
            (variable "GUIX_ELIXIR_LIBS")
            (files (list "lib/erlang/lib"
                         (string-append "lib/elixir/"
(version-major+minor version)))))
#+end_src

then, ~(setenv "ERL_LIBS" (getenv "GUIX_ERL_LIBS"))~ is not needed anymore.