docs: update extending dream2nix document to reflect module system changes

docs/src/extending-dream2nix.md

@@ -1,73 +1,31 @@
 # Extending dream2nix with external translators, builders etc.
 
-`dream2nix` can be extended while you are `init`ializing it. This can be done in a few ways.
-For extending, you need to utilize the `config.extra` option of the dream2nix config.
+`dream2nix` uses the NixOS module system for it's internal components.
+This means you can extend it using the module system.
+This can be done while the framework is being `init`ialized.
+To do this, you need to utilize the `config.modules` option of the dream2nix config.
 
-## Module System Transition
-The dream2nix architecture is currently in the process of being refactored into nixos modules. The actual APIs can deviate from what is described in this document.
-For up-to-date examples see `/examples/_d2n-extended` and `/examples/_d2n-extended-new-subsystem`
-Once the transition is completed we will update this document and remove this notice.
+## Declaring `modules`
 
-## Declare `extra`s from a nix file
+`config.modules` is a configuration option that expects paths to module files.
 
 ```nix
 dream2nix.lib.init {
-  # this also works around errors with function modules
-  # being declared here, which will be explained later.
-  config.extra = ./nix/d2n/extras.nix;
+  config.modules = [./nix/d2n/extras.nix];
 }
 ```
-this file should look like this:
+this file can look like this:
 ```nix
-{ dlib, lib, config, ... }:
+{ config, ... }:
+let
+  inherit (config) pkgs lib dlib;
+in
 {
-  subsystems.rust.translators.example-translator = ./rust-translator.nix;
+  translators.example-translator = {/* translator attrs */};
   # you can declare modules using functions here
-  fetchers.ipfs = {...}: {/* fetcher attrs */};
+  fetchers.ipfs = {/* fetcher attrs */};
 }
 ```
 
-See the [`d2n-extended-new-subsystem` example](https://github.com/nix-community/dream2nix/tree/main/examples/_d2n-extended-new-subsystem) for a basic example.
-
-## Declare `extra`s as an attribute set
-
-```nix
-dream2nix.lib.init {
-  config.extra = {
-    subsystems = {
-      # add new modules
-      ruby.discoverers.default = ./nix/d2n/ruby/discoverer.nix;
-      ruby.translators.bundix = ./nix/d2n/ruby/bundix.nix;
-      # existing modules can be overridden
-      rust.builders.crane = ./nix/d2n/rust/crane.nix;
-    };
-    # add new fetchers
-    fetchers.ipfs = ./nix/d2n/fetchers/ipfs.nix;
-    fetchers.gitea = ./nix/d2n/fetchers/gitea.nix;
-    # existing fetchers can be overridden
-    fetchers.http = ./nix/d2n/fetchers/http-proxied.nix;
-  };
-}
-```
-
-note: you can't declare modules using functions here.
-This is because the `config` may need to be serialized to JSON and passed around in impure situations (mostly impure translators).
-
-See the [`d2n-extended` example](https://github.com/nix-community/dream2nix/tree/main/examples/_d2n-extended/flake.nix) for a basic example.
-
-## Compose multiple different `extra`s
-
-This allows one to compose multiple `extra`s together with ease.
-The `dream2nixExtras` flake output in this case can be any of the approaches explained in this document for declaring `config.extra`.
-
-```nix
-dream2nix.lib.init {
-  # note: .dream2nixExtras is a hypothetical standardized flake output
-  # in practice this can be any flake output.
-  config.extra = [
-    haskellSubsystemFlake.dream2nixExtras
-    crystalSubsystemFlake.dream2nixExtras
-    gleamSubsystemFlake.dream2nixExtras
-  ];
-}
-```
+See the [`d2n-extended` example](https://github.com/nix-community/dream2nix/tree/main/examples/_d2n-extended) for an example on how to extend existing subsystems.
+See the [`d2n-extended-new-subsystem` example](https://github.com/nix-community/dream2nix/tree/main/examples/_d2n-extended-new-subsystem) for an example on how to implement a new subsystem.

src/modules/config/interface.nix

@@ -39,7 +39,7 @@ in {
       '';
     };
     modules = l.mkOption {
-      type = t.listOf (t.oneOf [t.attrs t.path (t.functionTo t.attrs)]);
+      type = t.listOf t.path;
       default = [];
       description = ''
         Extra modules to import in while evaluating the dream2nix framework.