Move ensure_branch out of _warn_on_[...] check

src/lakefs_spec/spec.py

@@ -8,6 +8,7 @@
 import os
 import urllib.error
 import urllib.request
+import warnings
 from contextlib import contextmanager
 from pathlib import Path
 from typing import Any, Generator
@@ -618,13 +619,15 @@ def __init__(
         )
 
         global _warn_on_fileupload
-        if mode == "wb" and _warn_on_fileupload:
-            logger.warning(
-                f"Calling `{self.__class__.__name__}.open()` in write mode results in unbuffered "
-                "file uploads, because the lakeFS Python client does not support multipart "
-                "uploads. Uploading large files unbuffered can have performance implications."
-            )
-            _warn_on_fileupload = False
+        if mode == "wb":
+            if _warn_on_fileupload:
+                warnings.warn(
+                    f"Calling `{self.__class__.__name__}.open()` in write mode results in unbuffered "
+                    "file uploads, because the lakeFS Python client does not support multipart "
+                    "uploads. Uploading large files unbuffered can have performance implications.",
+                    UserWarning,
+                )
+                _warn_on_fileupload = False
             repository, branch, resource = parse(path)
             ensure_branch(self.fs.client, repository, branch, self.fs.source_branch)
 

tests/test_lakefs_file.py

@@ -37,9 +37,13 @@ def test_lakefs_file_open_write(
 
     rpath = f"{repository}/{temp_branch}/{random_file.name}"
 
-    # try opening the remote file and writing to it
-    with fs.open(rpath, "wb") as fp:
-        fp.write(orig_text)
+    with pytest.warns(
+        UserWarning,
+        match=r"Calling `LakeFSFile\.open\(\)` in write mode results in unbuffered file uploads, because the lakeFS Python client does not support multipart uploads\. Uploading large files unbuffered can have performance implications\.",
+    ):
+        # try opening the remote file and writing to it
+        with fs.open(rpath, "wb") as fp:
+            fp.write(orig_text)
 
     # pulling the written file down again, using ONLY built-in open (!)
     lpath = random_file.with_name(random_file.name + "_copy")