Adding an editor

A consumer is one directory under modules/devix/consumers/. The directory is discovered automatically, and everything derived from it — the consumer list, the per-item exposure toggles, the defaultEditor candidates, the EDITOR/VISUAL map, the adapter lists both targets assemble from — follows without you editing anything else.

consumers/<name>/
  default.nix    what this consumer is (the registry entry)
  transform.nix  pure: resolved languages -> that tool's config format
  home.nix       Home Manager adapter
  devenv.nix     devenv adapter (optional)

1. The registry entry

# consumers/kakoune/default.nix
{
  description = "Kakoune text editor";

  # "all"  — configures languages generically, needs no per-language metadata
  # "meta" — only covers languages carrying consumerMeta.kakoune
  capability = "meta";

  # Types the `consumerMeta.kakoune` block in each language file. Required for
  # "meta" consumers; null for "all".
  metaOptions = lib: {
    filetypes = lib.mkOption {
      type = lib.types.listOf lib.types.str;
      default = [ ];
      description = "Kakoune filetype names for this language.";
    };
  };

  # When should this consumer switch itself on?
  activeWhen = config: config.programs.kakoune.enable or false;

  # Command for EDITOR/VISUAL, or null if this is not an interactive editor.
  editorCommand = "kak";

  home = ./home.nix;
  devenv = null;
}

Declaring capability = "meta" without metaOptions is rejected at evaluation time, so the two cannot drift apart.

2. The transform

Keep this pure — it takes resolved languages and returns the tool’s config. Being a plain function of lib makes it easy to reason about and to reuse across targets.

# consumers/kakoune/transform.nix
{ lib }:
let
  toKakoune = name: language: { ... };
in
{
  toKakouneConfig = languages: lib.mapAttrs toKakoune languages;
}

Languages arrive already filtered and resolved: only those enabled, exposed to you, and supported by your capability model, with their server and formatter lists already narrowed and the registry entries attached as lsps and formatterConfigs. Do not re-implement that filtering — it lives in consumers/registry.nix precisely so every consumer agrees.

3. The adapter

# consumers/kakoune/home.nix
{ config, lib, ... }:

let
  consumers = import ../registry.nix { inherit lib; };
  kakouneLib = import ./transform.nix { inherit lib; };

  cfg = config.devix;
  languages = consumers.languagesFor "kakoune" cfg.languages;
  resolved = consumers.resolveForConsumer "kakoune" cfg languages;
in
{
  config = lib.mkIf (cfg.enable && cfg.consumers.kakoune.enable && languages != { }) {
    programs.kakoune.settings = kakouneLib.toKakouneConfig resolved;
  };
}

The adapter does not need to enable itself — targets/home/auto-enable.nix derives that from your activeWhen for every consumer at once.

4. Teach the languages about it

For a "meta" consumer, add a consumerMeta.kakoune block to each language it should cover. Languages without one are skipped, which is a perfectly good resting state — support can grow language by language, and the support matrix shows the coverage at a glance.

Checking your work

nix eval --impure --expr '
  let lib = (import <nixpkgs> {}).lib;
  in (import ./modules/devix/consumers/registry.nix { inherit lib; }).names'

nix eval .#homeConfigurations.<user>.config.programs.kakoune.settings --json | jq

Your consumer should appear in names, gain a column in the support matrix, and show up as a toggle on every language, addon, server and formatter.