feat: upstream node generation

flake-modules/globals.nix

@@ -0,0 +1,74 @@
+{
+  inputs,
+  lib,
+  config,
+  ...
+}:
+let
+  inherit (lib) mkOption types;
+in
+{
+  options.globals = {
+    optModules = mkOption {
+      type = types.listOf types.deferredModule;
+      default = [ ];
+      description = ''
+        Modules defining global options.
+        These should not include any config only option declaration.
+        Will be included in the exported nixos Modules from this flake to be included
+        into the host evaluation.
+      '';
+    };
+    defModules = mkOption {
+      type = types.listOf types.deferredModule;
+      default = [ ];
+      description = ''
+        Modules configuring global options.
+        These should not include any option declaration use {option}`optModules` for that.
+        Will not included in the exported nixos Modules.
+      '';
+    };
+    attrkeys = mkOption {
+      type = types.listOf types.str;
+      default = [ ];
+      description = ''
+        The toplevel attrNames for your globals.
+        Make sure the keys of this attrset are trivially evaluatable to avoid infinite recursion,
+        therefore we inherit relevant attributes from the config.
+      '';
+    };
+  };
+  config.flake = flakeSubmod: {
+    globals =
+      let
+        globalsSystem = lib.evalModules {
+          prefix = [ "globals" ];
+          specialArgs = {
+            inherit (inputs.self.pkgs.x86_64-linux) lib;
+            inherit inputs;
+            inherit (flakeSubmod.config) nodes;
+          };
+          modules =
+            config.globals.optModules
+            ++ config.globals.defModules
+            ++ [
+              ../modules/globals.nix
+              (
+                { lib, ... }:
+                {
+                  globals = lib.mkMerge (
+                    lib.concatLists (
+                      lib.flip lib.mapAttrsToList flakeSubmod.config.nodes (
+                        name: cfg:
+                        builtins.addErrorContext "while aggregating globals from nixosConfigurations.${name} into flake-level globals:" cfg.config._globalsDefs
+                      )
+                    )
+                  );
+                }
+              )
+            ];
+        };
+      in
+      lib.genAttrs config.globals.attrkeys (x: globalsSystem.config.globals.${x});
+  };
+}