flake-parts/setups: refactor Disko integration

modules/flake-parts/setups/disko.nix

@@ -4,7 +4,7 @@
 # that. Take note we don't consider integrating this with declarative NixOS
 # setups since their Disko scripts are already gettable in
 # `config.system.build.diskoScript` along with its variants (e.g., `noDeps`).
-{ config, lib, ... }:
+{ config, lib, inputs, ... }:
 
 let
   cfg = config.setups.disko;
@@ -39,6 +39,40 @@ in
     };
   };
 
+  options.setups.nixos.configs =
+    let
+      diskoIntegrationModule = { config, lib, name, ... }: {
+        options = {
+          diskoConfigs = lib.mkOption {
+            type = with lib.types; listOf str;
+            default = [ ];
+            example = [ "external-hdd" ];
+            description = ''
+              A list of declarative Disko configurations to be included alongside
+              the NixOS configuration.
+            '';
+          };
+        };
+
+        config = lib.mkIf (config.diskoConfigs != [ ]) (
+          let
+            diskoConfigs =
+              builtins.map (name: import ../../../configs/disko/${name}) config.diskoConfigs;
+          in
+          {
+            modules = lib.singleton {
+              imports =
+                [ inputs.disko.nixosModules.disko ]
+                ++ (lib.lists.flatten diskoConfigs);
+            };
+          }
+        );
+      };
+    in
+    lib.mkOption {
+      type = with lib.types; attrsOf (submodule diskoIntegrationModule);
+    };
+
   config = {
     flake.diskoConfigurations =
       lib.mapAttrs (name: _: import ../../../configs/disko/${name}) cfg.configs;

modules/flake-parts/setups/nixos.nix

@@ -157,16 +157,6 @@ let
         };
       };
 
-      diskoConfigs = lib.mkOption {
-        type = with lib.types; listOf str;
-        default = [ ];
-        example = [ "external-hdd" ];
-        description = ''
-          A list of declarative Disko configurations to be included alongside
-          the NixOS configuration.
-        '';
-      };
-
       shouldBePartOfNixOSConfigurations = lib.mkOption {
         type = lib.types.bool;
         default = lib.isAttrs config.deploy || config.formats == null;
@@ -184,19 +174,6 @@ let
       # Bring in the required modules.
       ../../../configs/nixos/${config.configName}
 
-      # Then we include the Disko configuration (if there's any).
-      (lib.mkIf (config.diskoConfigs != [ ]) (
-        let
-          diskoConfigs =
-            builtins.map (name: import ../../../configs/disko/${name}) config.diskoConfigs;
-        in
-        {
-          imports =
-            [ inputs.disko.nixosModules.disko ]
-            ++ (lib.lists.flatten diskoConfigs);
-        })
-      )
-
       # Setting up the typical configuration.
       (
         { config, lib, ... }: {