Add state-version option

checks/flake-module.nix

@@ -10,6 +10,7 @@ in
   imports = filter pathExists [
     ./backups/flake-module.nix
     ../nixosModules/clanCore/machine-id/tests/flake-module.nix
+    ../nixosModules/clanCore/state-version/tests/flake-module.nix
     ./devshell/flake-module.nix
     ./flash/flake-module.nix
     ./impure/flake-module.nix

nixosModules/clanCore/default.nix

@@ -19,6 +19,7 @@
       ./nixos-facter.nix
       ./vm.nix
       ./machine-id
+      ./state-version
       ./wayland-proxy-virtwl.nix
       ./zerotier
       ./zfs.nix

nixosModules/clanCore/state-version/default.nix

@@ -0,0 +1,31 @@
+{
+  lib,
+  config,
+  ...
+}:
+let
+  var = config.clan.core.vars.generators.state-version.files.version or { };
+in
+{
+  options.clan.core.settings.state-version = {
+    enable = lib.mkEnableOption "automatic state-version generation.
+
+    The option will take the specified version, if one is already supplied through
+    the config or generate one if not.
+    ";
+  };
+
+  config = lib.mkIf (config.clan.core.settings.state-version.enable) {
+    system.stateVersion = lib.mkDefault (lib.removeSuffix "\n" var.value);
+    clan.core.vars.generators.state-version = {
+      files.version = {
+        secret = false;
+        value = lib.mkDefault config.system.nixos.release;
+      };
+      runtimeInputs = [ ];
+      script = ''
+        echo -n ${config.system.stateVersion} > "$out"/version
+      '';
+    };
+  };
+}

nixosModules/clanCore/state-version/tests/flake-module.nix

@@ -0,0 +1,38 @@
+{ ... }:
+{
+  perSystem =
+    { ... }:
+    {
+      clan.nixosTests.state-version = {
+
+        name = "state-version";
+
+        clan = {
+          directory = ./.;
+
+          # Workaround until we can use nodes.server = { };
+          modules."@clan/importer" = ../../../../clanServices/importer;
+
+          inventory = {
+            machines.server = { };
+            instances.importer = {
+              module.name = "@clan/importer";
+              roles.default.tags.all = { };
+              roles.default.extraModules = [
+                {
+                  clan.core.settings.state-version.enable = true;
+                }
+              ];
+            };
+          };
+        };
+
+        # TODO: Broken. Use instead of importer after fixing.
+        # nodes.server = { };
+
+        # This is not an actual vm test, this is a workaround to
+        # generate the needed vars for the eval test.
+        testScript = "";
+      };
+    };
+}

nixosModules/clanCore/state-version/tests/sops/users/admin/key.json

@@ -0,0 +1,4 @@
+{
+  "publickey": "age1qm0p4vf9jvcnn43s6l4prk8zn6cx0ep9gzvevxecv729xz540v8qa742eg",
+  "type": "age"
+}

nixosModules/clanCore/state-version/tests/vars/per-machine/server/state-version/version/value

@@ -0,0 +1 @@
+25.11