nixpkgs/nixos/lib/eval-config.nix
Robert Hensing 693e2c3287 nixos/eval-config: Remove statically known mkIf
mkIf is unnecessary when the condition is statically known - that is
knowable before entering the module evaluation.

By changing this to a precomputed module, we support changing the
defined options to readOnly options.
2023-05-10 15:55:09 +02:00

117 lines
3.9 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
evalConfigArgs@
{ # !!! system can be set modularly, would be nice to remove,
# however, removing or changing this default is too much
# of a breaking change. To set it modularly, pass `null`.
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?
# we can add modules that are included in specialisations, regardless
# of inheritParentConfig.
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
, modulesLocation ? (builtins.unsafeGetAttrPos "modules" evalConfigArgs).file or null
, # !!! 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 pkgs_ = pkgs;
in
let
inherit (lib) optional;
evalModulesMinimal = (import ./default.nix {
inherit lib;
# Implicit use of feature is noted in implementation.
featureFlags.minimalModules = { };
}).evalModules;
pkgsModule = rec {
_file = ./eval-config.nix;
key = _file;
config = lib.mkMerge (
(optional (system != null) {
# 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;
})
++
(optional (pkgs_ != null) {
_module.args.pkgs = lib.mkForce pkgs_;
})
);
};
withWarnings = x:
lib.warnIf (evalConfigArgs?extraArgs) "The extraArgs argument to eval-config.nix is deprecated. Please set config._module.args instead."
lib.warnIf (evalConfigArgs?check) "The check argument to eval-config.nix is deprecated. Please set config._module.check instead."
x;
legacyModules =
lib.optional (evalConfigArgs?extraArgs) {
config = {
_module.args = extraArgs;
};
}
++ lib.optional (evalConfigArgs?check) {
config = {
_module.check = lib.mkDefault check;
};
};
allUserModules =
let
# Add the invoking file (or specified modulesLocation) as error message location
# for modules that don't have their own locations; presumably inline modules.
locatedModules =
if modulesLocation == null then
modules
else
map (lib.setDefaultModuleLocation modulesLocation) modules;
in
locatedModules ++ legacyModules;
noUserModules = evalModulesMinimal ({
inherit prefix specialArgs;
modules = baseModules ++ extraModules ++ [ pkgsModule modulesModule ];
});
# Extra arguments that are useful for constructing a similar configuration.
modulesModule = {
config = {
_module.args = {
inherit noUserModules baseModules extraModules modules;
};
};
};
nixosWithUserModules = noUserModules.extendModules { modules = allUserModules; };
in
withWarnings nixosWithUserModules // {
inherit extraArgs;
inherit (nixosWithUserModules._module.args) pkgs;
}