In my configuration.nix I have the following option:
machineVariants = lib.options.mkOption {
type = lib.types.listOf lib.types.str;
example = ''[ "d" "l" ]'';
default = [ "d" "l" ];
description = lib.mdDoc
"The machines for which system configurations can be generated by this configuration.";
};
In my hardware-configuration.nix-like, I have the following option:
machineLabel = lib.options.mkOption {
type = lib.types.nullOr (lib.types.enum config.machineVariants);
example = "d";
default = null;
description = lib.mdDoc "Host machine selection.";
};
In my root.nix (the nix file which routes to configuration.nix after doing some initial setup), I have the following specialisations defined:
config = let
genSpecialization = machineLabel: {
inheritParentConfig = true;
configuration = { config = { inherit machineLabel; }; };
};
in {
specialisation =
lib.attrsets.genAttrs config.machineVariants genSpecialization;
...
and ultimately all of this comes together to be used in my hardware-configuration.nix-like file:
config = let
machineSpecificSettings = {
d = {
availableKernelModules =
[ "xhci_pci" "ahci" "usb_storage" "usbhid" "sd_mod" ];
kernelModules = [ "kvm-intel" ];
homeFs = "3T";
lidSwitch = { };
cpuFreqGovernor = "performance";
firmwareFamily = "intel";
};
l = {
availableKernelModules =
[ "nvme" "xhci_pci" "ahci" "usb_storage" "sd_mod" "sdhci_pci" ];
kernelModules = [ "kvm-amd" ];
homeFs = "FS";
lidSwitch = { lidSwitch = "hibernate"; };
cpuFreqGovernor = "ondemand";
firmwareFamily = "amd";
};
};
thisMachineSettings = if (builtins.isNull config.machineLabel) then
builtins.throw "config.machineLabel is NULL!"
else
machineSpecificSettings."${config.machineLabel}";
in
...
However, running my setup triggers the the throw in the last code snippet, which is activated when builtins.isNull config.machineLabel is true. I am evaluating+activating the system using effectively the following command:
sudo nixos-rebuild switch --show-trace --specialisations d
Any ideas on why the specialisation flag does not trigger the machineLabel to be set correctly?