nixpkgs/nixos/lib/eval-config.nix
Silvan Mosberger b77d8ead28
Merge pull request #51850 from roberth/nixos-pure
nixos/lib/eval-config.nix: Add extraModules parameter for opt-in purity
2020-08-24 04:29:37 +02:00

74 lines
2.6 KiB
Nix

# From an end-user configuration file (`configuration.nix'), 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 ? {}
, # !!! See comment about args in lib/modules.nix
specialArgs ? {}
, modules
, # !!! See comment about check in lib/modules.nix
check ? true
, prefix ? []
, lib ? import ../../lib
, extraModules ? let e = builtins.getEnv "NIXOS_EXTRA_MODULE_PATH";
in if e == "" then [] else [(import e)]
}:
let extraArgs_ = extraArgs; pkgs_ = pkgs;
in
let
pkgsModule = rec {
_file = ./eval-config.nix;
key = _file;
config = {
# Explicit `nixpkgs.system` or `nixpkgs.localSystem` should override
# this. Since the latter defaults to the former, the former should
# default to the argument. That way this new default could propagate all
# they way through, but has the last priority behind everything else.
nixpkgs.system = lib.mkDefault system;
# Stash the value of the `system` argument. When using `nesting.children`
# we want to have the same default value behavior (immediately above)
# without any interference from the user's configuration.
nixpkgs.initialSystem = system;
_module.args.pkgs = lib.mkIf (pkgs_ != null) (lib.mkForce pkgs_);
};
};
in rec {
# Merge the option definitions in all modules, forming the full
# system configuration.
inherit (lib.evalModules {
inherit prefix check;
modules = baseModules ++ extraModules ++ [ pkgsModule ] ++ modules;
args = extraArgs;
specialArgs =
{ modulesPath = builtins.toString ../modules; } // specialArgs;
}) config options _module;
# These are the extra arguments passed to every module. In
# particular, Nixpkgs is passed through the "pkgs" argument.
extraArgs = extraArgs_ // {
inherit baseModules extraModules modules;
};
inherit (_module.args) pkgs;
}