data model: add run-time configuration

deployment/data-model-test.nix

@@ -11,17 +11,18 @@ let
     }).config;
 in
 {
+  _class = "nix-unit";
+
   test-eval = {
     expr =
       let
         example = eval {
-          runtime-environments.bar.nixos = {
-            module =
-              { ... }:
-              {
-                system.stateVersion = "25.05";
-              };
-          };
+          runtime-configurations.nixos =
+            { ... }:
+            {
+              system.stateVersion = "25.05";
+            };
+          runtime-environments.bar.nixos = { };
           applications.foo = {
             module =
               { pkgs, ... }:
@@ -34,11 +35,13 @@ in
         };
       in
       {
-        has-runtime = lib.isAttrs example.runtime-environments.bar.nixos.module;
+        has-runtime-configuration = lib.isAttrs example.runtime-configurations.nixos;
+        has-runtime-environment = lib.isAttrs example.runtime-environments.bar.nixos.module;
         has-application = lib.isAttrs example.applications.foo.module;
       };
     expected = {
-      has-runtime = true;
+      has-runtime-configuration = true;
+      has-runtime-environment = true;
       has-application = true;
     };
   };

deployment/data-model.nix

@@ -1,43 +1,68 @@
 {
   lib,
+  config,
   ...
 }:
 let
-  inherit (lib) types mkOption;
-in
-with types;
-{
-  options = {
-    runtime-environments = mkOption {
-      description = "Collection of runtime environments into which applications can be deployed";
-      type = attrsOf (attrTag {
-        nixos = mkOption {
-          description = "A single NixOS machine";
-          type = submodule {
-            options = {
-              module = mkOption {
-                description = "The NixOS module describing the base configuration for that machine";
-                type = deferredModule;
-              };
-            };
-          };
-        };
-      });
+  inherit (lib) attrNames mkOption genAttrs;
+  inherit (lib.types)
+    attrsOf
+    attrTag
+    deferredModule
+    submoduleWith
+    ;
+  runtime-configuration = mkOption {
+    description = "The NixOS module of a run-time environment";
+    type = deferredModule;
+    default = {
+      _class = "nixos";
     };
-    applications = mkOption {
-      description = "Collection of Fediversity applications";
-      type = attrsOf (submoduleWith {
+  };
+  runtime-environment = attrTag {
+    nixos = mkOption {
+      type = submoduleWith {
         modules = [
           {
             options = {
               module = mkOption {
-                description = "The NixOS module for that application, for configuring that application";
+                description = "The NixOS module of the run-time environment";
                 type = deferredModule;
+                default = config.runtime-configurations.nixos;
+                readOnly = true;
               };
             };
           }
         ];
-      });
+      };
+    };
+  };
+  application = submoduleWith {
+    description = "A Fediversity application";
+    modules = [
+      {
+        options = {
+          module = mkOption {
+            description = "The NixOS module for that application, for configuring that application";
+            type = deferredModule;
+          };
+        };
+      }
+    ];
+  };
+in
+{
+  options = {
+    runtime-configurations = mkOption {
+      description = "Collection of runtime environments into which applications can be deployed";
+      type = attrTag (genAttrs (attrNames runtime-environment.nestedTypes) (_: runtime-configuration));
+    };
+    runtime-environments = mkOption {
+      description = "Collection of runtime environments into which applications can be deployed";
+      type = attrsOf runtime-environment;
+    };
+    applications = mkOption {
+      description = "Collection of Fediversity applications";
+      type = attrsOf application;
     };
   };
 }