fix(volume): normalize path-like roots and error union typing

Signed-off-by: Aakash Saravanan <aakash.saravanan@databricks.com>

Author: aakash-saravanan-db

src/databricks/sql/backend/kernel/_errors.py

@@ -152,6 +152,7 @@ def reraise_kernel_error(
             "diagnostic-info": getattr(exc, "diagnostic_info", None),
         }
     message = getattr(exc, "message", str(exc))
+    new: Union[Error, FileNotFoundError]
     # Local missing files have no HTTP status; remote missing files carry 404.
     if (
         file_transfer

src/databricks/sql/backend/kernel/client.py

@@ -22,6 +22,7 @@
 
 import inspect
 import logging
+import os
 import re
 import threading
 import uuid
@@ -588,11 +589,11 @@ def execute_command(
                     )
                 stmt.set_sql(operation)
                 allowed_paths = cursor.connection.staging_allowed_local_path
-                if isinstance(allowed_paths, str):
+                if isinstance(allowed_paths, (str, os.PathLike)):
                     allowed_paths = [allowed_paths]
                 set_paths = getattr(stmt, "set_staging_allowed_local_paths", None)
                 if callable(set_paths):
-                    set_paths(allowed_paths or [])
+                    set_paths([os.fsdecode(path) for path in allowed_paths or []])
                 elif _is_staging_statement(operation):
                     raise NotSupportedError(
                         "Volume transfers require a databricks-sql-kernel wheel "

tests/unit/test_kernel_client.py

@@ -15,6 +15,7 @@
 
 import sys
 import types
+from pathlib import Path
 from typing import Optional
 from unittest.mock import MagicMock
 
@@ -810,6 +811,8 @@ def test_execute_command_forwards_row_limit(row_limit):
     [
         (None, []),
         ("/tmp/files", ["/tmp/files"]),
+        (Path("/tmp/files"), ["/tmp/files"]),
+        ([Path("/tmp/a"), Path("/tmp/b")], ["/tmp/a", "/tmp/b"]),
         (["/tmp/a", "/tmp/b"], ["/tmp/a", "/tmp/b"]),
     ],
 )