feat: Allow import-trees to be used in argument as if they were paths.

README.md

@@ -101,8 +101,10 @@ The following is valid usage:
 }
 ```
 
+Other import-tree objects can also be given as arguments (or in lists) as if they were paths.
+
 As an special case, when the single argument given to an `import-tree` object is an
-attribute-set *-it is _NOT_ a path or list of paths-*, the `import-tree` object
+attribute-set containing an `options` attribute, the `import-tree` object
 assumes it is being evaluated as a module. This way, a pre-configured `import-tree` can
 also be used directly in a list of module imports.
 

checkmate.nix

@@ -166,6 +166,17 @@ in
             res.config.hello;
           expected = "world";
         };
+
+        import-tree."test can take other import-trees as if they were paths" = {
+          expr = (lit.filter (lib.hasInfix "mod")).leafs [
+            (it.addPath ./tree/modules/hello-option)
+            ./tree/modules/hello-world
+          ];
+          expected = [
+            ./tree/modules/hello-option/mod.nix
+            ./tree/modules/hello-world/mod.nix
+          ];
+        };
       };
 
     }

default.nix

@@ -29,12 +29,14 @@ let
         lib: root:
         let
           initialFilter = andNot (lib.hasInfix "/_") (lib.hasSuffix ".nix");
+          listFilesRecursive = x: if isImportTree x then treeFiles x else lib.filesystem.listFilesRecursive x;
+          treeFiles = t: (t.withLib lib).leafs.result;
         in
         lib.pipe
           [ paths root ]
           [
             (lib.lists.flatten)
-            (map lib.filesystem.listFilesRecursive)
+            (map listFilesRecursive)
             (lib.lists.flatten)
             (builtins.filter (compose (and filterf initialFilter) toString))
             (map mapf)
@@ -60,13 +62,11 @@ let
     attrs: k: f:
     attrs // { ${k} = f attrs.${k}; };
 
-  functor =
-    self: path:
-    let
-      imported-as-module = builtins.isAttrs path;
-      arg = if imported-as-module then [ ] else path;
-    in
-    perform self.__config arg;
+  isImportTree = and (x: x ? __config.__functor) builtins.isAttrs;
+
+  inModuleEval = and (x: x ? options) builtins.isAttrs;
+
+  functor = self: arg: perform self.__config (if inModuleEval arg then [ ] else arg);
 
   callable =
     let