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# From an end-user configuration file (`configuration'), build a NixOS
# configuration object (`config') from which we can retrieve option
# values.
{ system ? builtins.currentSystem
, pkgs ? null
, baseModules ? import ../modules/module-list.nix
, extraArgs ? {}
, modules
, nixpkgs ? <nixpkgs>
}:
let extraArgs_ = extraArgs; pkgs_ = pkgs; system_ = system; in
rec {
# These are the NixOS modules that constitute the system configuration.
configComponents = modules ++ baseModules;
# 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;
optionDefinitions = systemModule.config;
optionDeclarations = systemModule.options;
inherit (systemModule) options;
# These are the extra arguments passed to every module. In
# particular, Nixpkgs is passed through the "pkgs" argument.
extraArgs = extraArgs_ // {
inherit pkgs modules baseModules;
modulesPath = ../modules;
pkgs_i686 = import nixpkgs { system = "i686-linux"; };
utils = import ./utils.nix pkgs;
};
# Import Nixpkgs, allowing the NixOS option nixpkgs.config to
# specify the Nixpkgs configuration (e.g., to set package options
# such as firefox.enableGeckoMediaPlayer, or to apply global
# overrides such as changing GCC throughout the system), and the
# option nixpkgs.system to override the platform type. This is
# tricky, because we have to prevent an infinite recursion: "pkgs"
# is passed as an argument to NixOS modules, but the value of "pkgs"
# depends on config.nixpkgs.config, which we get from the modules.
# So we call ourselves here with "pkgs" explicitly set to an
# instance that doesn't depend on nixpkgs.config.
pkgs =
if pkgs_ != null
then pkgs_
else import nixpkgs (
let
system = if nixpkgsOptions.system != "" then nixpkgsOptions.system else system_;
nixpkgsOptions = (import ./eval-config.nix {
inherit system extraArgs modules;
# For efficiency, leave out most NixOS modules; they don't
# define nixpkgs.config, so it's pointless to evaluate them.
baseModules = [ ../modules/misc/nixpkgs.nix ];
pkgs = import nixpkgs { system = system_; config = {}; };
}).optionDefinitions.nixpkgs;
in
{
inherit system;
inherit (nixpkgsOptions) config;
});
# Optionally check wether all config values have corresponding
# option declarations.
config =
let doCheck = optionDefinitions.environment.checkConfigurationOptions; in
assert doCheck -> pkgs.lib.checkModule "" systemModule;
systemModule.config;
}
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