* Move the config evaluation into a separate expression so that it can

be reused, e.g. for building the CD/DVD.

svn path=/nixos/branches/modular-nixos/; revision=15744

default.nix

@@ -9,29 +9,14 @@ let
   nixpkgs = fromEnv "NIXPKGS" /etc/nixos/nixpkgs;
 
   pkgs = import nixpkgs {system = builtins.currentSystem;};
-  
-  configComponents = [
-    configuration
-    (import ./system/options.nix)
-  ];
 
-  # Make a configuration object from which we can retrieve option
+  inherit
-  # values.
+    (import ./lib/eval-config.nix {inherit configuration pkgs;})
-  config =
+    config optionDeclarations;
-    pkgs.lib.fixOptionSets
-      pkgs.lib.mergeOptionSets
-      pkgs configComponents;
 
-  optionDeclarations =
-    pkgs.lib.fixOptionSetsFun
-      pkgs.lib.filterOptionSets
-      pkgs configComponents
-      config;
-  
 in
 
 {
-
   # Optionally check wether all config values have corresponding
   # option declarations.
   system = pkgs.checker config.system.build.system

lib/eval-config.nix

@@ -0,0 +1,23 @@
+# From an end-user configuration file (`configuration'), build a NixOS
+# configuration object (`config') from which we can retrieve option
+# values.
+
+{configuration, pkgs}:
+
+rec {
+  configComponents = [
+    configuration
+    (import ../system/options.nix)
+  ];
+
+  config =
+    pkgs.lib.fixOptionSets
+      pkgs.lib.mergeOptionSets
+      pkgs configComponents;
+
+  optionDeclarations =
+    pkgs.lib.fixOptionSetsFun
+      pkgs.lib.filterOptionSets
+      pkgs configComponents
+      config;
+}