1 files changed, 61 insertions, 4 deletions
diff --git a/nixpkgs/nixos/modules/programs/rust-motd.nix b/nixpkgs/nixos/modules/programs/rust-motd.nix
index d5f1820ba752..4c9b1018596b 100644
--- a/nixpkgs/nixos/modules/programs/rust-motd.nix
+++ b/nixpkgs/nixos/modules/programs/rust-motd.nix
@@ -5,6 +5,23 @@ with lib;
 let
   cfg = config.programs.rust-motd;
   format = pkgs.formats.toml { };
+
+  # Order the sections in the TOML according to the order of sections
+  # in `cfg.order`.
+  motdConf = pkgs.runCommand "motd.conf"
+    {
+      __structuredAttrs = true;
+      inherit (cfg) order settings;
+      nativeBuildInputs = [ pkgs.remarshal pkgs.jq ];
+    }
+    ''
+      cat "$NIX_ATTRS_JSON_FILE" \
+        | jq '.settings as $settings
+              | .order
+              | map({ key: ., value: $settings."\(.)" })
+              | from_entries' -r \
+        | json2toml /dev/stdin "$out"
+    '';
 in {
   options.programs.rust-motd = {
     enable = mkEnableOption (lib.mdDoc "rust-motd");
@@ -27,10 +44,43 @@ in {
         For possible formats, please refer to {manpage}`systemd.time(7)`.
       '';
     };
+    order = mkOption {
+      type = types.listOf types.str;
+      default = attrNames cfg.settings;
+      defaultText = literalExpression "attrNames cfg.settings";
+      description = mdDoc ''
+        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
+        {
+          uptime = { /* ... */ };
+          banner = { /* ... */ };
+        }
+        ```
+
+        will still have `banner` displayed before `uptime`.
+
+        To work around that, this option can be used to define the order of all keys,
+        i.e.
+
+        ```nix
+        {
+          order = [
+            "uptime"
+            "banner"
+          ];
+        }
+        ```
+
+        makes sure that `uptime` is placed before `banner` in the motd.
+      '';
+    };
     settings = mkOption {
-      type = 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)
@@ -45,14 +95,21 @@ in {
           `programs.rust-motd` is incompatible with `users.motd`!
         '';
       }
+      { 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`.
+        '';
+      }
     ];
     systemd.services.rust-motd = {
       path = with pkgs; [ bash ];
       documentation = [ "https://github.com/rust-motd/rust-motd/blob/v${pkgs.rust-motd.version}/README.md" ];
       description = "motd generator";
+      wantedBy = [ "multi-user.target" ];
       serviceConfig = {
         ExecStart = "${pkgs.writeShellScript "update-motd" ''
-          ${pkgs.rust-motd}/bin/rust-motd ${format.generate "motd.conf" cfg.settings} > motd
+          ${pkgs.rust-motd}/bin/rust-motd ${motdConf} > motd
         ''}";
         CapabilityBoundingSet = [ "" ];
         LockPersonality = true;