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{yen}

Flake outputs

yen does not know what a flake is. The root kind declares an out sink with merge, and yen.flake gives the flake’s outputs. Each sink with an out key gives its part.

modules/fleet.nix
# The `out` sink of the root is the flake: `yen.flake` gives it.
{ yen, ... }:
{
  yen.kinds.fleet = {
    spawns.host = _: yen.host;
    sinks.out.reduce = yen.lib.reduce.merge;
  };
  yen.kinds.host.sinks.services.out =
    { host, services, ... }:
    {
      services.${host.name} = services;
    };
  yen.fleet.main = { };
  yen.host.web = { };
  yen.host.db = { };
  yen.flake = { out, ... }: out;
}

Read the outputs

Section titled “Read the outputs”

The out arg is the flake itself, read lazily. An element can build on other outputs without inputs.self:

modules/aspects.nix
{ yen, lib, ... }:
{
  yen.aspects.nginx = {
    at = yen.host.web;
    services = "nginx";
  };
  yen.aspects.postgres = {
    at = yen.host.db;
    services = "postgres";
  };
  # the `out` arg: an element reads the flake outputs, lazily. No `inputs.self`.
  yen.aspects.inventory = {
    at = yen.kinds.fleet;
    out =
      { out, ... }:
      {
        inventory = lib.concatLists (lib.attrValues out.services);
      };
  };
}
result
{
  inventory = [
    "postgres"
    "nginx"
  ];
  services = {
    db = [
      "postgres"
    ];
    web = [
      "nginx"
    ];
  };
}

With or without flakes

Section titled “With or without flakes”

(import yen).lib.mkFlake module gives the flake outputs. (import yen).lib.eval module gives every query, and flake is one of them. mkFlake m is (eval m).flake.

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