73f18fd42f
This is useful for adding extra functionality or defaults to _every_ nixos evaluation. My use case is overriding behaviour for all nixos tests, for example setting packageOverrides to newer versions and changing some default dependencies/settings. By making this accessible through an environment variable, this can now be fully accomplished externally. No more need to fork nixos/nixpkgs (which becomes a maintenance burden), just use the channel instead and plug in via this envvar.
73 lines
2.8 KiB
Nix
73 lines
2.8 KiB
Nix
# From an end-user configuration file (`configuration'), build a NixOS
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# configuration object (`config') from which we can retrieve option
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# values.
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{ system ? builtins.currentSystem
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, pkgs ? null
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, baseModules ? import ../modules/module-list.nix
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, extraArgs ? {}
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, modules
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, check ? true
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, prefix ? []
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}:
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let extraArgs_ = extraArgs; pkgs_ = pkgs; system_ = system;
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extraModules = let e = builtins.getEnv "NIXOS_EXTRA_MODULE_PATH";
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in if e == "" then [] else [(import (builtins.toPath e))];
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in rec {
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# Merge the option definitions in all modules, forming the full
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# system configuration.
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inherit (pkgs.lib.evalModules {
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inherit prefix;
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modules = modules ++ extraModules ++ baseModules;
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args = extraArgs;
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check = check && options.environment.checkConfigurationOptions.value;
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}) config options;
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# These are the extra arguments passed to every module. In
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# particular, Nixpkgs is passed through the "pkgs" argument.
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# FIXME: we enable config.allowUnfree to make packages like
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# nvidia-x11 available. This isn't a problem because if the user has
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# ‘nixpkgs.config.allowUnfree = false’, then evaluation will fail on
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# the 64-bit package anyway. However, it would be cleaner to respect
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# nixpkgs.config here.
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extraArgs = extraArgs_ // {
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inherit pkgs modules baseModules;
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modulesPath = ../modules;
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pkgs_i686 = import ./nixpkgs.nix { system = "i686-linux"; config.allowUnfree = true; };
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utils = import ./utils.nix pkgs;
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};
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# Import Nixpkgs, allowing the NixOS option nixpkgs.config to
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# specify the Nixpkgs configuration (e.g., to set package options
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# such as firefox.enableGeckoMediaPlayer, or to apply global
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# overrides such as changing GCC throughout the system), and the
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# option nixpkgs.system to override the platform type. This is
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# tricky, because we have to prevent an infinite recursion: "pkgs"
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# is passed as an argument to NixOS modules, but the value of "pkgs"
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# depends on config.nixpkgs.config, which we get from the modules.
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# So we call ourselves here with "pkgs" explicitly set to an
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# instance that doesn't depend on nixpkgs.config.
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pkgs =
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if pkgs_ != null
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then pkgs_
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else import ./nixpkgs.nix (
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let
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system = if nixpkgsOptions.system != "" then nixpkgsOptions.system else system_;
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nixpkgsOptions = (import ./eval-config.nix {
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inherit system extraArgs modules prefix;
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# For efficiency, leave out most NixOS modules; they don't
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# define nixpkgs.config, so it's pointless to evaluate them.
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baseModules = [ ../modules/misc/nixpkgs.nix ../modules/config/no-x-libs.nix ];
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pkgs = import ./nixpkgs.nix { system = system_; config = {}; };
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check = false;
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}).config.nixpkgs;
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in
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{
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inherit system;
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inherit (nixpkgsOptions) config;
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});
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}
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