nixos/facter: add core library and system detection (#454237)

  ...

}:

{

  imports = [

    ./system.nix

  ];

  meta.maintainers = with lib.maintainers; [ mic92 ];

  options.hardware.facter = with lib; {

# Internal library functions for hardware.facter modules

# Eventually we can think about moving this under lib/

# These are facter-specific helpers for querying nixos-facter reports

lib:

let

  inherit (lib) assertMsg;

  # Query if a facter report contains a CPU with the given vendor name

  hasCpu =

    name:

    {

      hardware ? { },

      ...

    }:

    let

      cpus = hardware.cpu or [ ];

    in

    assert assertMsg (hardware != { }) "no hardware entries found in the report";

    assert assertMsg (cpus != [ ]) "no cpu entries found in the report";

    builtins.any (

      {

        vendor_name ? null,

        ...

      }:

      assert assertMsg (vendor_name != null) "detail.vendor_name not found in cpu entry";

      vendor_name == name

    ) cpus;

  # Extract all driver_modules from a list of hardware entries

  collectDrivers = list: lib.catAttrs "driver_modules" list;

  # Convert number to zero-padded 4-digit hex string (for USB device IDs)

  toZeroPaddedHex =

    n:

    let

      hex = lib.toHexString n;

      len = builtins.stringLength hex;

    in

    if len == 1 then

      "000${hex}"

    else if len == 2 then

      "00${hex}"

    else if len == 3 then

      "0${hex}"

    else

      hex;

in

{

  inherit

    hasCpu

    collectDrivers

    toZeroPaddedHex

    ;

  hasAmdCpu = hasCpu "AuthenticAMD";

  hasIntelCpu = hasCpu "GenuineIntel";

}

{

  config,

  options,

  lib,

  ...

}:

{

  # Skip setting hostPlatform in test VMs where it's read-only

  # Tests have virtualisation.test options and import read-only.nix

  config.nixpkgs = lib.optionalAttrs (!(options ? virtualisation.test)) {

    hostPlatform = lib.mkIf (

      config.hardware.facter.report.system or null != null && !options.nixpkgs.pkgs.isDefined

    ) (lib.mkDefault config.hardware.facter.report.system);

  };

}