Unverified Commit d77b59b4 authored by Maximilian Bosch's avatar Maximilian Bosch
Browse files

nixos/rust-motd: use a second attribute (`order`) for the of sections in TOML 

Rather than using `priority` with `sortProperties`, a new option called
`order` defines the ordering of the sections. I.e.

    order = [ "global" "uptime" "banner" ]

means that `uptime` comes before `banner`. Please note that `global` is
for global settings and not a section. I figured that it'd be too much
magic to hide this in the implementation and ask the user to specify the
order of _each_ section in `settings` instead.

OTOH this makes the intent way clearer than priorities. Also, this
remains opt-in, the option defaults to `attrNames cfg.settings`, i.e.
all sections ordered alphabetically.
parent 214cf0b9

nixos/modules/programs/rust-motd.nix

+44 −29
Original line number Diff line number Diff line
@@ -8,12 +8,13 @@ let 


  orderedSections = listToAttrs

    (imap0

      (i: items@{ sectionHeader, ... }: nameValuePair "env${toString i}" {

        ${sectionHeader} = removeAttrs items [ "priority" "sectionHeader" ];

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

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

      })

      (sortProperties (mapAttrsToList (k: v: v // { sectionHeader = k; }) cfg.settings)));

      cfg.order);



  # Order the sections in the TOML according to the `priority` field.

  # 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
@@ -54,35 +55,42 @@ in { 
        For possible formats, please refer to {manpage}`systemd.time(7)`.

      '';

    };

    settings = mkOption {

      type = types.attrsOf (types.submodule {

        freeformType = format.type;

        options.priority = mkOption {

          type = types.int;

          default = modules.defaultOrderPriority;

    order = mkOption {

      type = types.listOf types.str;

      default = attrNames cfg.settings;

      defaultText = literalExpression "attrNames cfg.settings";

      description = mdDoc ''

            In `rust-motd`, the order of the sections in TOML correlates to the order

            of the items displayed in the resulting `motd`. Attributes in Nix are

            ordered alphabetically, e.g. `banner` would always be before `uptime`.

        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

        ordered alphabetically internally this means that



        ```nix

        {

          uptime = { /* ... */ };

          banner = { /* ... */ };

        }

        ```



            To change that, this option can be used. The lower this number is, the higher

            is the priority and the more a section is at the top of the message.

        will still have `banner` displayed before `uptime`.



            For instance

        To work around that, this option can be used to define the order of all keys,

        i.e.



        ```nix

        {

              banner.command = "hostname | figlet -f slant";

              uptime = {

                prefix = "Up";

                priority = 0;

              };

          order = [

            "uptime"

            "banner"

          ];

        }

        ```



            would make the `uptime` appear before the banner.

        makes sure that `uptime` is placed before `banner` in the motd.

      '';

    };

    settings = mkOption {

      type = types.attrsOf (types.submodule {

        freeformType = format.type;

      });

      description = mdDoc ''

        Settings on what to generate. Please read the
@@ -98,6 +106,13 @@ in { 
          `programs.rust-motd` is incompatible with `users.motd`!

        '';

      }

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

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

        message = ''

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

          `programs.rust-motd.order`.

        '';

      }

    ];

    systemd.services.rust-motd = {

      path = with pkgs; [ bash ];