Prevent copying folders into itself

finder/admin/folder.py

@@ -237,10 +237,10 @@ def copy_inodes(self, request, folder_id):
         current_folder = self.get_object(request, folder_id)
         inode_ids = body.get('inode_ids', [])
         for inode in FolderModel.objects.filter_inodes(id__in=inode_ids):
-            if next(current_folder.listdir(name=inode.name, is_folder=True), None):
-                msg = gettext("A folder named “{name}” already exists in destination folder.")
-                return HttpResponseBadRequest(msg.format(name=inode.name), status=409)
-            inode.copy_to(current_folder, owner=request.user)
+            try:
+                inode.copy_to(current_folder, owner=request.user)
+            except RecursionError as exc:
+                return HttpResponseBadRequest(str(exc), status=409)
         return JsonResponse({
             'inodes': self.get_inodes(parent=current_folder),
         })

finder/models/folder.py

@@ -159,6 +159,11 @@ def copy_to(self, folder, **kwargs):
         """
         Copies the folder to a destination folder and returns it.
         """
+        for ancestor in folder.ancestors:
+            if ancestor.id == self.id:
+                msg = "Folder named “{source}” can not become the descendant of destination folder “{target}”."
+                raise RecursionError(gettext(msg).format(source=self.name, target=folder.name))
+
         kwargs.setdefault('name', self.name)
         kwargs.setdefault('owner', self.owner)
         kwargs.update(parent=folder)