How to expose host-dependent top-level outputs in den?

[HPCesia]

Hi everyone,

I am currently migrating my Nix configuration from a custom flake-parts implementation (Dendritic pattern) to den.

I encounter a scenario where I need to expose top-level flake outputs that depend on specific attributes of the defined hosts. Specifically, I use deploy-rs for remote deployment and need to generate a deploy output for every host where deployable = true.

The logic looks roughly like this (with flake-parts):

{inputs, self, ...}: {
  flake.deploy.nodes.${host.name} = {
    hostname = host.name;
    profiles.system.path = inputs.deploy-rs.lib.${host.system}.activate.nixos self.nixosConfigurations.${host.name};
  };
}

What is the idiomatic way to achieve this in den?

[vic]

Hey @HPCesia, all those attributes you need in your code snippet host.{system,name} exist on the host schema (you can also add new free-form attributes to them in case you need it, or use den.base.host to add module typed options to all hosts schema).

I see your flake output looks like it can already be a function of host,

nodeDeploy = name: host: {
    hostname = host.hostName;
    profiles.system.path = inputs.deploy-rs.lib.${host.system}.activate.nixos self.nixosConfigurations.${name};
};

flake.deploy.nodes = mapAttrs nodeDeploy den.hosts.x86_64-linux;

that's the easiest way I might believe.