horribly cobble together the ability to use both home-manager switch and nixos-rebuild switch against the same flake

lib/default.nix

@@ -1,68 +1,113 @@
-{ nixpkgs, home-manager, inputs, ... }:
+{
+  nixpkgs,
+  home-manager,
+  inputs,
+  ...
+}:
 let
   allOverlays = import (../overlays) { inherit nixpkgs; };
-in
-{
-  # It's not really that I care about whether a system is a desktop system or
-  # a server system, but moreso that I care about whether a system is headless or not.
-  # I also care about things like if it's darwin, or wsl.
-  # TODO: Expand this to actually make use of extraSpecialArgs and pass special
-  # args to the relevant places.
-  mkSystem = {
-    hostname,
-    system ? "x86_64-linux",
-    users ? [],
-    extraModules ? [],
-    extraSpecialArgs ? {}
-  }:
-  let
-    pkgs_with_overlays = import nixpkgs {
+  getPkgs =
+    system:
+    import nixpkgs {
       inherit system;
       overlays = allOverlays;
     };
-    hostModule = import ../hosts/${hostname} {
-      inherit inputs;
-      pkgs = pkgs_with_overlays;
-    };
-    userModules = map (name:
-      import ../users/${name} {
-        pkgs = pkgs_with_overlays;
-        lib = nixpkgs.lib;
-      }
-    ) users;
-
-    homeUserNames = builtins.filter (name:
-      builtins.pathExists ../users/${name}/home.nix
-    ) users;
-
-    homeUsers = nixpkgs.lib.listToAttrs (map (name: {
-      name = name;
-      value = import ../users/${name}/home.nix {
-        username = name;
-        pkgs = pkgs_with_overlays;
-        lib = nixpkgs.lib;
+in
+{
+  mkSystem =
+    {
+      hostname,
+      system ? "x86_64-linux",
+      users ? [ ],
+      extraModules ? [ ],
+      homeUsers ? { },
+      extraSpecialArgs ? { },
+    }:
+    let
+      pkgs_with_overlays = import nixpkgs {
+        inherit system;
+        overlays = allOverlays;
       };
-    }) homeUserNames);
-  in
+      hostModule = import ../hosts/${hostname} {
+        inherit inputs;
+        pkgs = pkgs_with_overlays;
+      };
+      userModules = map (
+        name:
+        import ../users/${name} {
+          pkgs = pkgs_with_overlays;
+          lib = nixpkgs.lib;
+        }
+      ) users;
+
+      formattedHomeUsers = nixpkgs.lib.mapAttrs (username: moduleList: {
+        imports = moduleList;
+      }) homeUsers;
+    in
     nixpkgs.lib.nixosSystem {
       inherit system;
-      # pkgs = import inputs.nixpkgs {
-      #   inherit system;
-      #   overlays = allOverlays;
-      #   config = { allowUnfree = true; nvidia.acceptLicense = true; };
-      # };
-      modules = [ hostModule ]
-        ++ userModules
-        ++ extraModules
-        ++ (if homeUserNames != [] then [
-          home-manager.nixosModules.home-manager
-          {
-            home-manager.backupFileExtension = "hm-bak";
-            home-manager.users = homeUsers;
-          }
-        ] else []);
+      modules = [
+        hostModule
+      ]
+      ++ userModules
+      ++ extraModules
+      ++ (
+        if homeUsers != { } then
+          [
+            home-manager.nixosModules.home-manager
+            {
+              #home-manager.useGlobalPkgs = true;  # NOTE: Incompatible with nixpkgs.{config,overlays}
+              home-manager.useUserPackages = true;
+              home-manager.backupFileExtension = "hm-bak";
+
+              # Directly inject the module lists? (isn't this the problem?)
+              home-manager.users = formattedHomeUsers;
+              home-manager.extraSpecialArgs = { inherit inputs; };
+            }
+          ]
+        else
+          [ ]
+      );
       specialArgs = {
         inherit inputs hostname;
-      } // extraSpecialArgs;
+      }
+      // extraSpecialArgs;
     };
+
+  getUserHomeModule =
+    username: pkgs: inputs:
+    import ../users/${username}/home.nix {
+      inherit username pkgs inputs;
+      lib = nixpkgs.lib;
+    };
+
+  /**
+    This function returns an attribute set { module, config }.
+  */
+  mkHome =
+    {
+      username,
+      system ? "x86_64-linux",
+      extraModules ? [ ],
+    }:
+    let
+      pkgs_with_overlays = getPkgs system;
+      moduleList = [
+        (import ../users/${username}/home.nix {
+          inherit inputs username;
+          pkgs = pkgs_with_overlays;
+          lib = nixpkgs.lib;
+        })
+      ]
+      ++ extraModules;
+    in
+    {
+      module = moduleList;
+      config = home-manager.lib.homeManagerConfiguration {
+        pkgs = pkgs_with_overlays;
+        modules = moduleList;
+      };
+    };
+
+  mkHomeConfigs = userProfiles: nixpkgs.lib.mapAttrs (username: profile: profile.config) userProfiles;
 }