Configurable Nix Flakes

Currently nix flakes do not inherently support specifying configurable options for the outputs of a flake. This is an attempt to work around this by using the NixOS module system to declare and later specifying options.

This is very much work in progress

This flake provides one output lib which currently contains two nix functions:

lib.configurableFlake: inputs -> {options, config} -> outputBuilder -> outputs

This function takes the flake inputs, then an attrset of options declarations (options) and definitions (config) and then a function that gets the evaluated config as well as the inputs and returns the output of the flake.

lib.withSystems: inputs -> [<system>] -> outputBuilder -> outputs

This is a shorthand only taking the inputs, a list of supported systems and an outputBuilder as above. config is automatically filled with systems being a list of the supplied systems.

outputs.withConfig: config -> outputs

Flakes that are constructed with the above functions will have a function withConfig that can be called to derive a flake with different configurations options. This makes using an existing flake with a different configuration as easy as:

{
  description =
    "Example of using a flake with a different configuration";
  inputs.someConfigurableFlake.url = "someurl";
  outputs = {self, someConfigurableFlake}:
    someConfigurableFlake.withConfig {
      supportFoo = true;
    };
}