[Nix-dev] joining attribute sets recursively

[Florian Friesdorf]

Hi,

I'd like to extend power-management.nix with an aggressive setting:

      aggressive = mkOption {
        default = false;
        description =
          ''
            Whether to enable aggressive power management features. An
            area for experimentation. Please send feedback about this
            to the list.
          '';
      };

and:

config = mkIf cfg.enable {
  ...
  powerManagement.cpuFreqGovernor = "ondemand";
} // cfg.aggressive ? {
  ...
  powerManagement.scsiLinkPolicy = "min_power";
} : {};

Now for one the syntax is incorrect and for another
powerManagement.cpuFreqGovernor would not be set, as powerManagement
will be overriden with the value from the second attribute set.

Is there a way to recursively merge attribute sets, so that
cpuFreqGovernor and scsiLinkPolicy would be set in powerManagement?

How can I achieve the conditional merge?

I tried:

config = mkIf cfg.enable ({
  ...
} // (if cfg.aggressive then {
  ...
} else { }));

--> infinite recursion

regards
florian
-- 
Florian Friesdorf <flo at chaoflow.net>
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