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nixpkgs/nixos/lib/eval-config.nix
Shea Levy 0a0a29fd0b Add comments about the module system interface
Ideally the module system could be configured pretty much completely by
the contents of the modules themselves, so add comments about avoiding
complicating it further and possibly removing now-redundant
configurability from the existing interface.
2015-03-12 23:42:57 +01:00

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# From an end-user configuration file (`configuration'), build a NixOS
# configuration object (`config') from which we can retrieve option
# values.
# !!! Please think twice before adding to this argument list!
# Ideally eval-config.nix would be an extremely thin wrapper
# around lib.evalModules, so that modular systems that have nixos configs
# as subcomponents (e.g. the container feature, or nixops if network
# expressions are ever made modular at the top level) can just use
# types.submodule instead of using eval-config.nix
{ # !!! system can be set modularly, would be nice to remove
system ? builtins.currentSystem
, # !!! is this argument needed any more? The pkgs argument can
# be set modularly anyway.
pkgs ? null
, # !!! what do we gain by making this configurable?
baseModules ? import ../modules/module-list.nix
, # !!! See comment about args in lib/modules.nix
extraArgs ? {}
, modules
, # !!! See comment about check in lib/modules.nix
check ? true
, prefix ? []
, lib ? import ../../lib
}:
let extraArgs_ = extraArgs; pkgs_ = pkgs; system_ = system;
extraModules = let e = builtins.getEnv "NIXOS_EXTRA_MODULE_PATH";
in if e == "" then [] else [(import (builtins.toPath e))];
in
let
pkgsModule = rec {
_file = ./eval-config.nix;
key = _file;
config = {
nixpkgs.system = lib.mkDefault system_;
};
};
in rec {
# Merge the option definitions in all modules, forming the full
# system configuration.
inherit (lib.evalModules {
inherit prefix check;
modules = modules ++ extraModules ++ baseModules ++ [ pkgsModule ];
args = extraArgs;
}) config options;
# These are the extra arguments passed to every module. In
# particular, Nixpkgs is passed through the "pkgs" argument.
# FIXME: we enable config.allowUnfree to make packages like
# nvidia-x11 available. This isn't a problem because if the user has
# nixpkgs.config.allowUnfree = false, then evaluation will fail on
# the 64-bit package anyway. However, it would be cleaner to respect
# nixpkgs.config here.
extraArgs = extraArgs_ // {
inherit pkgs modules baseModules;
modulesPath = ../modules;
pkgs_i686 = import ./nixpkgs.nix { system = "i686-linux"; config.allowUnfree = true; };
utils = import ./utils.nix pkgs;
};
pkgs =
if pkgs_ != null
then pkgs_
else import ./nixpkgs.nix (
let
system = if nixpkgsOptions.system != "" then nixpkgsOptions.system else system_;
nixpkgsOptions = config.nixpkgs;
in
{
inherit system;
inherit (nixpkgsOptions) config;
});
}