1 files changed, 82 insertions, 0 deletions
diff --git a/nixos/modules/misc/nixos.nix b/nixos/modules/misc/nixos.nix
new file mode 100644
index 000000000000..356129211d06
--- /dev/null
+++ b/nixos/modules/misc/nixos.nix
@@ -0,0 +1,82 @@
+{ config, options, lib, ... }:
+
+# This modules is used to inject a different NixOS version as well as its
+# argument such that one can pin a specific version with the versionning
+# system of the configuration.
+let
+  nixosReentry = import config.nixos.path {
+    inherit (config.nixos) configuration extraModules;
+    inherit (config.nixpkgs) system;
+    reEnter = true;
+  };
+in
+
+with lib;
+
+{
+  options = {
+    nixos.path = mkOption {
+      default = null;
+      example = literalExample "./nixpkgs-15.09/nixos";
+      type = types.nullOr types.path;
+      description = ''
+        This option give the ability to evaluate the current set of modules
+        with a different version of NixOS. This option can be used version
+        the version of NixOS with the configuration without relying on the
+        <literal>NIX_PATH</literal> environment variable.
+      '';
+    };
+
+    nixos.system = mkOption {
+      example = "i686-linux";
+      type = types.uniq types.str;
+      description = ''
+        Name of the system used to compile NixOS.
+      '';
+    };
+
+    nixos.extraModules = mkOption {
+      default = [];
+      example = literalExample "mkIf config.services.openssh.enable [ ./sshd-config.nix ]";
+      type = types.listOf types.unspecified;
+      description = ''
+        Define additional modules which would be loaded to evaluate the
+        configuration.
+      '';
+    };
+
+    nixos.configuration = mkOption {
+      type = types.unspecified;
+      internal = true;
+      description = ''
+        Option used by <filename>nixos/default.nix</filename> to re-inject
+        the same configuration module as the one used for the current
+        execution.
+      '';
+    };
+
+    nixos.reflect = mkOption {
+      default = { inherit config options; };
+      type = types.unspecified;
+      internal = true;
+      description = ''
+        Provides <literal>config</literal> and <literal>options</literal>
+        computed by the module system and given as argument to all
+        modules. These are used for introspection of options and
+        configuration by tools such as <literal>nixos-option</literal>.
+      '';
+    };
+  };
+
+  config = mkMerge [
+    (mkIf (config.nixos.path != null) (mkForce {
+      system.build.toplevel = nixosReentry.system;
+      system.build.vm = nixosReentry.vm;
+      nixos.reflect = { inherit (nixosReentry) config options; };
+    }))
+
+    { meta.maintainers = singleton lib.maintainers.pierron;
+      meta.doc = ./nixos.xml;
+    }
+  ];
+}