feat: Pass nix-config as self to avoid infinite recursion

This change makes it possible to use this nix-config in all the
different ways imaginable (containers, bare metal, tests, and as a
separate flake input) *without* running into infinite recursion
issues with self.

It does this by using a trick similar to JavaScript in which
`var self = this;`, thus enabling the usage of "this" (or self, in
Nix's case) where it wouldn't otherwise be possible.

Note that this *only* works if the input for this repository is named
nix-config. This makes it impractical to combine with multiple
configurations that employ the same strategy.

flake.nix

@@ -40,7 +40,7 @@
     nixosConfigurations = {
       nixos = nixosSystem {
         system = "x86_64-linux";
-        specialArgs = attrs;
+        specialArgs = attrs // { nix-config = self; };
         modules = [
           ./hardware/laptop.nix
           {

modules/containers.nix

@@ -1,4 +1,4 @@
-{ config, stylix, home-manager, sakaya, ... }:
+{ config, nix-config, sakaya, ... }:
 
 let
   inherit (config.modules.system) username;
@@ -39,8 +39,7 @@ let
     ];
 
     specialArgs = {
-      inherit home-manager;
-      inherit stylix;
+      inherit nix-config;
     };
   };
 in

modules/desktop.nix

@@ -1,4 +1,4 @@
-{ home-manager, stylix, pkgs, config, lib, ... }:
+{ nix-config, pkgs, config, lib, ... }:
 
 let
   inherit (lib) mkEnableOption mkIf mkMerge;
@@ -14,8 +14,8 @@ let
 in
 {
   imports = attrValues {
-    inherit (home-manager.nixosModules) home-manager;
-    inherit (stylix.nixosModules) stylix;
+    inherit (nix-config.inputs.home-manager.nixosModules) home-manager;
+    inherit (nix-config.inputs.stylix.nixosModules) stylix;
   };
 
   options.modules.desktop = {

modules/system.nix

@@ -1,14 +1,19 @@
-{ pkgs, lib, config, ... }:
+{ nix-config, pkgs, lib, config, ... }:
 
 let
   inherit (lib) mkOption;
   inherit (lib.types) str listOf;
   inherit (pkgs.nixVersions) nix_2_19;
   inherit (cfg) username;
+  inherit (builtins) attrValues;
 
   cfg = config.modules.system;
 in
 {
+  imports = attrValues {
+    inherit (nix-config.inputs.home-manager.nixosModules) home-manager;
+  };
+
   options.modules.system = {
     username = mkOption {
       type = str;

tests/lib.nix

@@ -8,6 +8,7 @@ in
   defaults.documentation.enable = lib.mkDefault false;
   node.specialArgs = {
     inherit self;
+    nix-config = self;
   };
   imports = [ test ];
 }).config.result