Unverified Commit 57de6a85 authored by Maximilian Bosch's avatar Maximilian Bosch
Browse files

nixos/rust-motd: refactor assertion and TOML generation 



* `sort (<)` also works for strings (TIL!), so no need for comparing
  length and whether all keys from `cfg.settings` exist in `cfg.order`
  (slightly less overhead).

* Don't build another piece of JSON (`orderedSections`), simply use
  `cfg.settings`/`cfg.order` with `__structuredAttrs` to ensure a
  properly ordered TOML.

  This also has the upside of not having to do quote hackery.

* Also, a freeform submodule isn't strictly needed because we don't have
  any special options defined, so replacing that with
  `attrsOf format.type`.

Co-authored-by: default avatarSilvan Mosberger <github@infinisil.com>
parent d77b59b4

nixos/modules/programs/rust-motd.nix

+13 −25
Original line number Diff line number Diff line
@@ -6,31 +6,20 @@ let 
  cfg = config.programs.rust-motd;

  format = pkgs.formats.toml { };



  orderedSections = listToAttrs

    (imap0

      (i: attr: nameValuePair "env${toString i}" {

        ${attr} = cfg.settings.${attr};

      })

      cfg.order);



  # Order the sections in the TOML according to the order of sections

  # in `cfg.order`.

  # This is done by

  # * creating an attribute set with keys `env0`/`env1`/.../`envN`

  #   where `env0` contains the first section and `envN` the last

  #   (in the form of `{ sectionName = { /* ... */ }}`)

  # * the declarations of `env0` to `envN` in ascending order are

  #   concatenated with `jq`. Now we have a JSON representation of

  #   the config in the correct order.

  # * this is piped to `json2toml` to get the correct format for rust-motd.

  motdConf = pkgs.runCommand "motd.conf"

    (orderedSections // {

    {

      __structuredAttrs = true;

      inherit (cfg) order settings;

      nativeBuildInputs = [ pkgs.remarshal pkgs.jq ];

    })

    }

    ''

      cat "$NIX_ATTRS_JSON_FILE" \

        | jq '${concatMapStringsSep " + " (key: ''."${key}"'') (attrNames orderedSections)}' \

        | jq '.settings as $settings

              | .order

              | map({ key: ., value: $settings."\(.)" })

              | from_entries' -r \

        | json2toml /dev/stdin "$out"

    '';

in {
@@ -60,8 +49,10 @@ in { 
      default = attrNames cfg.settings;

      defaultText = literalExpression "attrNames cfg.settings";

      description = mdDoc ''

        The order of the sections in [](#opt-programs.rust-motd.settings) implies

        the order of sections in the motd. Since attribute sets in Nix are always

        The order of the sections in [](#opt-programs.rust-motd.settings).

        By default they are ordered alphabetically.



        Context: since attribute sets in Nix are always

        ordered alphabetically internally this means that



        ```nix
@@ -89,9 +80,7 @@ in { 
      '';

    };

    settings = mkOption {

      type = types.attrsOf (types.submodule {

        freeformType = format.type;

      });

      type = types.attrsOf format.type;

      description = mdDoc ''

        Settings on what to generate. Please read the

        [upstream documentation](https://github.com/rust-motd/rust-motd/blob/main/README.md#configuration)
@@ -106,8 +95,7 @@ in { 
          `programs.rust-motd` is incompatible with `users.motd`!

        '';

      }

      { assertion = length cfg.order == length (attrNames cfg.settings)

          && all (section: cfg.settings?${section}) cfg.order;

      { assertion = sort (a: b: a < b) cfg.order == attrNames cfg.settings;

        message = ''

          Please ensure that every section from `programs.rust-motd.settings` is present in

          `programs.rust-motd.order`.