use filename for uploaded files (#1774)

Co-authored-by: Ashley <[email protected]>

Author: codomposer

README.md

@@ -302,3 +302,4 @@ helpful and collaborative way.
 [slack-community]: https://slackcommunity.com/
 [files_upload_v2]: https://github.com/slackapi/python-slack-sdk/releases/tag/v3.19.0
 [aiohttp]: https://aiohttp.readthedocs.io/
+

slack_sdk/web/internal_utils.py

@@ -345,11 +345,11 @@ def _to_v2_file_upload_item(upload_file: Dict[str, Any]) -> Dict[str, Optional[A
     if filename is None:
         # use the local filename if filename is missing
         if isinstance(file, (str, os.PathLike)):
-            filename = os.fspath(file).split(os.path.sep)[-1]
+            filename = os.path.basename(os.fspath(file))
         else:
             filename = "Uploaded file"
 
-    title = upload_file.get("title", "Uploaded file")
+    title = upload_file.get("title")
     if data is None:
         raise SlackRequestError(f"File content not found for filename: {filename}, title: {title}")