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Big cleanup of the NixOS module system

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The major changes are:

* The evaluation is now driven by the declared options.  In
  particular, this fixes the long-standing problem with lack of
  laziness of disabled option definitions.  Thus, a configuration like

    config = mkIf false {
      environment.systemPackages = throw "bla";
    };

  will now evaluate without throwing an error.  This also improves
  performance since we're not evaluating unused option definitions.

* The implementation of properties is greatly simplified.

* There is a new type constructor "submodule" that replaces
  "optionSet".  Unlike "optionSet", "submodule" gets its option
  declarations as an argument, making it more like "listOf" and other
  type constructors.  A typical use is:

    foo = mkOption {
      type = type.attrsOf (type.submodule (
        { config, ... }:
        { bar = mkOption { ... };
          xyzzy = mkOption { ... };
        }));
    };

  Existing uses of "optionSet" are automatically mapped to
  "submodule".

* Modules are now checked for unsupported attributes: you get an error
  if a module contains an attribute other than "config", "options" or
  "imports".

* The new implementation is faster and uses much less memory.
This commit is contained in:
Eelco Dolstra 2013-10-28 00:56:22 +01:00
parent f4dadc5df8
commit 0e333688ce
9 changed files with 294 additions and 974 deletions
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13
nixos/lib/eval-config.nix
View file

@ -19,11 +19,9 @@ rec {
# Merge the option definitions in all modules, forming the full
# system configuration. It's not checked for undeclared options.
systemModule =
pkgs.lib.fixMergeModules configComponents extraArgs;
pkgs.lib.evalModules configComponents extraArgs;
optionDefinitions = systemModule.config;
optionDeclarations = systemModule.options;
inherit (systemModule) options;
config = systemModule.config;
# These are the extra arguments passed to every module. In
# particular, Nixpkgs is passed through the "pkgs" argument.
@ -56,16 +54,11 @@ rec {
# define nixpkgs.config, so it's pointless to evaluate them.
baseModules = [ ../modules/misc/nixpkgs.nix ];
pkgs = import ./nixpkgs.nix { system = system_; config = {}; };
}).optionDefinitions.nixpkgs;
}).config.nixpkgs;
in
{
inherit system;
inherit (nixpkgsOptions) config;
});
# Optionally check wether all config values have corresponding
# option declarations.
config =
assert optionDefinitions.environment.checkConfigurationOptions -> pkgs.lib.checkModule "" systemModule;
systemModule.config;
}