Allow functions for NixOS or home-manager configurations

This allows a configuration to be set as a function that will be passed
autoloadArgs. This is useful when each configuration is in its own file
when autoloading.

api_guide.md

@@ -617,6 +617,10 @@ outputs for NixOS systems and home-manager users.
 
 They should be set to an attribute set of respective configurations.
 
+Alternatively, the configurations can be functions, in which case those
+functions will be passed `autoloadArgs` and must return a standard
+configuration (this is useful when using autoloads with the `nixDir` feature).
+
 For example:
 
 ```nix
@@ -646,6 +650,20 @@ For example:
 }
 ```
 
+Optionally, defining as a function:
+
+```nix
+{
+  inputs.flakelight.url = "github:accelbread/flakelight";
+  outputs = { flakelight, ... }:
+    flakelight ./. {
+      nixosConfigurations.system = { lib, ... }: lib.nixosSystem {
+        # nixosSystem arguments
+      };
+    };
+}
+```
+
 ### nixosModules, homeModules, and flakelightModules
 
 The `nixosModules`, `homeModules`, and `flakelightModules` options allow you to

builtinModules/homeConfigurations.nix

@@ -2,12 +2,13 @@
 # Copyright (C) 2023 Archit Gupta <archit@accelbread.com>
 # SPDX-License-Identifier: MIT
 
-{ config, lib, ... }:
+{ config, lib, flakelight, autoloadArgs, ... }:
 let
-  inherit (builtins) isAttrs;
+  inherit (builtins) isAttrs mapAttrs;
   inherit (lib) foldl mapAttrsToList mergeOneOption mkOption mkOptionType mkIf
     recursiveUpdate;
   inherit (lib.types) lazyAttrsOf;
+  inherit (flakelight.types) optFunctionTo;
 
   homeConfiguration = mkOptionType {
     name = "homeConfiguration";
@@ -19,16 +20,17 @@ let
 in
 {
   options.homeConfigurations = mkOption {
-    type = lazyAttrsOf homeConfiguration;
+    type = lazyAttrsOf (optFunctionTo homeConfiguration);
     default = { };
   };
 
   config.outputs = mkIf (config.homeConfigurations != { }) {
-    inherit (config) homeConfigurations;
+    homeConfigurations = mapAttrs (_: f: f autoloadArgs)
+      config.homeConfigurations;
     checks = foldl recursiveUpdate { } (mapAttrsToList
       (n: v: {
         ${v.config.nixpkgs.system}."home-${n}" = v.activationPackage;
       })
-      config.homeConfigurations);
+      (mapAttrs (_: f: f autoloadArgs) config.homeConfigurations));
   };
 }

builtinModules/nixosConfigurations.nix

@@ -2,12 +2,13 @@
 # Copyright (C) 2023 Archit Gupta <archit@accelbread.com>
 # SPDX-License-Identifier: MIT
 
-{ config, lib, ... }:
+{ config, lib, flakelight, autoloadArgs, ... }:
 let
-  inherit (builtins) isAttrs;
+  inherit (builtins) isAttrs mapAttrs;
   inherit (lib) foldl mapAttrsToList mergeOneOption mkIf mkOption mkOptionType
     recursiveUpdate;
   inherit (lib.types) lazyAttrsOf;
+  inherit (flakelight.types) optFunctionTo;
 
   nixosConfiguration = mkOptionType {
     name = "nixosConfiguration";
@@ -21,17 +22,18 @@ let
 in
 {
   options.nixosConfigurations = mkOption {
-    type = lazyAttrsOf nixosConfiguration;
+    type = lazyAttrsOf (optFunctionTo nixosConfiguration);
     default = { };
   };
 
   config.outputs = mkIf (config.nixosConfigurations != { }) {
-    inherit (config) nixosConfigurations;
+    nixosConfigurations = mapAttrs (_: f: f autoloadArgs)
+      config.nixosConfigurations;
     checks = foldl recursiveUpdate { } (mapAttrsToList
       (n: v: {
         ${v.config.nixpkgs.system}."nixos-${n}" =
           v.config.system.build.toplevel;
       })
-      config.nixosConfigurations);
+      (mapAttrs (_: f: f autoloadArgs) config.nixosConfigurations));
   };
 }