Commit 6c8c88c6 authored by Asherah Connor's avatar Asherah Connor
Browse files

buildMix: default to removing target config 

See previous discussion at https://github.com/NixOS/nixpkgs/pull/429770.
cc @adamcstephens.

This is equivalent to giving `appConfigPath` an empty directory, but
expresses intent better (and doesn't require throwing an empty directory
into the store).

The Elixir ecosystem assumes [1] that dependencies are compiled without
their config; the `config/` directory is therefore used in library-only
projects to supply config values only intended for use when _developing_
them.  This leads to errors only seen in Nix when compile-time config
lacks runtime equivalents in end-user applications (per the whole
conversation at [1]).

Right now, the only way to get `buildMix` to build without config is to
manually remove the target's config directory in a hook/override, or (as
above) give `appConfigPath` an empty directory.  This PR adds a clearer
mechanism, and makes it the default.

[1] https://github.com/dashbitco/lazy_html/pull/11#issuecomment-3138715485

Tested with a `mix2nix`-using package that this functions as expected,
and with some `deps_nix`-using ones that `appConfigPath` still does too.
parent ed33ba16

pkgs/development/beam-modules/build-mix.nix

+13 −3
Original line number Diff line number Diff line
@@ -25,12 +25,15 @@ 
  meta ? { },

  enableDebugInfo ? false,

  mixEnv ? "prod",

  removeConfig ? true,

  # A config directory that is considered for all the dependencies of an app, typically in $src/config/

  # This was initially added, as some of Mobilizon's dependencies need to access the config at build time.

  appConfigPath ? null,

  ...

}@attrs:



assert appConfigPath != null -> removeConfig;



let

  shell =

    drv:
@@ -79,10 +82,17 @@ let 
            runHook preConfigure



            ${./mix-configure-hook.sh}

            ${lib.optionalString (removeConfig && isNull appConfigPath)

              # By default, we don't want to include whatever config a dependency brings; per

              # https://hexdocs.pm/elixir/main/Config.html, config is application specific.

              ''

                rm -rf config

                mkdir config

              ''

            }

            ${lib.optionalString (!isNull appConfigPath)

              # Due to https://hexdocs.pm/elixir/main/Config.html the config directory

              # of a library seems to be not considered, as config is always

              # application specific. So we can safely delete it.

              # Some more tightly-coupled dependencies do depend on the config of the application

              # they're being built for.

              ''

                rm -rf config

                cp -r ${appConfigPath} config