modules: export also core modules

modules/flake-parts/all-modules.nix

@@ -46,7 +46,7 @@ in {
   imports = flakePartsModules;
 
   options.flake.modules = mkOption {
-    type = types.lazyAttrsOf types.raw;
+    type = types.lazyAttrsOf (types.lazyAttrsOf types.raw);
   };
 
   # generates future flake outputs: `modules.<kind>.<module-name>`

modules/flake-parts/core-modules.nix

@@ -0,0 +1,33 @@
+# Automatically exports modules from the `/**/modules` directory to:
+#   `flake.modules.<kind>.<name>`
+# Automatically imports all flake-parts modules from `/**/modules/flake-parts`
+{
+  config,
+  lib,
+  self,
+  ...
+}: let
+  # inherit all lib functions used below
+  inherit
+    (builtins)
+    readDir
+    ;
+  inherit
+    (lib)
+    mapAttrs'
+    filterAttrs
+    nameValuePair
+    removeSuffix
+    ;
+
+  mapModules = path:
+    mapAttrs'
+    (fn: _:
+      nameValuePair
+      (removeSuffix ".nix" fn)
+      (path + "/${fn}"))
+    (filterAttrs (_: type: type == "regular" || type == "directory") (readDir path));
+in {
+  # generates future flake outputs: `modules.<kind>.<module-name>`
+  config.flake.modules.dream2nix = mapModules (self + "/modules/dream2nix/core");
+}