[Nix-dev] nixos modules: Setting attrsOf sub-options

[Rickard Nilsson]

Hi,

I'm stuck on the following problem with the NixOS module system:

Say I have an option definition like this:

   let
     subOpts = { ... }: {
       options = {
         opt1 = mkOption { ... };
         opt2 = mkOption { ... };
       };
     };

   in {
     options = {
       top = mkOption {
         type = with types; attrsOf (submodule subOpts);
         default = {};
       };
     };
   }

Then I use it like this:

   top = {
     one.opt1 = ...;
     two.opt1 = ...;
   };

And now I want to set top.*.opt2 in a separate module, based on the 
existing attributes. Essentially something like this:

   top = mkMerge (
     map (a: { ${a}.opt2 = f a; }) (attrNames config.top)
   )

But of course, the above results in an infinite recursion since I'm 
using config.top in its own definition.

What I want is simply to be able to plug in a module that defines some 
sub-options without having explicit knowledge about the attribute set.

Does anyone know a way of achieveing this?


   / Rickard