make description mandatory, not Optional

Signed-off-by: varun-edachali-dbx <varun.edachali@databricks.com>

Author: varun-edachali-dbx

src/databricks/sql/backend/sea/backend.py

@@ -290,7 +290,7 @@ def get_allowed_session_configurations() -> List[str]:
 
     def _extract_description_from_manifest(
         self, manifest: ResultManifest
-    ) -> Optional[List]:
+    ) -> List[Tuple]:
         """
         Extract column description from a manifest object, in the format defined by
         the spec: https://peps.python.org/pep-0249/#description
@@ -299,15 +299,12 @@ def _extract_description_from_manifest(
             manifest: The ResultManifest object containing schema information
 
         Returns:
-            Optional[List]: A list of column tuples or None if no columns are found
+            List[Tuple]: A list of column tuples
         """
 
         schema_data = manifest.schema
         columns_data = schema_data.get("columns", [])
 
-        if not columns_data:
-            return None
-
         columns = []
         for col_data in columns_data:
             # Format: (name, type_code, display_size, internal_size, precision, scale, null_ok)
@@ -323,7 +320,7 @@ def _extract_description_from_manifest(
                 )
             )
 
-        return columns if columns else None
+        return columns
 
     def _results_message_to_execute_response(
         self, response: GetStatementResponse

src/databricks/sql/backend/types.py

@@ -423,7 +423,7 @@ class ExecuteResponse:
 
     command_id: CommandId
     status: CommandState
-    description: Optional[List[Tuple]] = None
+    description: List[Tuple]
     has_been_closed_server_side: bool = False
     lz4_compressed: bool = True
     is_staging_operation: bool = False

src/databricks/sql/result_set.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from abc import ABC, abstractmethod
-from typing import List, Optional, TYPE_CHECKING
+from typing import List, Optional, TYPE_CHECKING, Tuple
 
 import logging
 import pandas
@@ -50,7 +50,7 @@ def __init__(
         has_been_closed_server_side: bool = False,
         is_direct_results: bool = False,
         results_queue=None,
-        description=None,
+        description: List[Tuple] = [],
         is_staging_operation: bool = False,
         lz4_compressed: bool = False,
         arrow_schema_bytes: Optional[bytes] = None,

src/databricks/sql/utils.py

@@ -61,7 +61,7 @@ def build_queue(
         max_download_threads: int,
         ssl_options: SSLOptions,
         lz4_compressed: bool = True,
-        description: Optional[List[Tuple]] = None,
+        description: List[Tuple] = [],
     ) -> ResultSetQueue:
         """
         Factory method to build a result set queue.
@@ -117,7 +117,7 @@ def build_queue(
         sea_result_data: ResultData,
         manifest: Optional[ResultManifest],
         statement_id: str,
-        description: Optional[List[Tuple[Any, ...]]] = None,
+        description: List[Tuple] = [],
         schema_bytes: Optional[bytes] = None,
         max_download_threads: Optional[int] = None,
         sea_client: Optional[SeaDatabricksClient] = None,
@@ -274,7 +274,7 @@ def __init__(
         start_row_offset: int = 0,
         result_links: Optional[List[TSparkArrowResultLink]] = None,
         lz4_compressed: bool = True,
-        description: Optional[List[Tuple]] = None,
+        description: List[Tuple] = [],
     ):
         """
         A queue-like wrapper over CloudFetch arrow batches.

tests/unit/test_client.py

@@ -100,6 +100,7 @@ def test_closing_connection_closes_commands(self, mock_thrift_client_class):
                 )
                 mock_execute_response.has_been_closed_server_side = closed
                 mock_execute_response.is_staging_operation = False
+                mock_execute_response.description = []
 
                 # Mock the backend that will be used by the real ThriftResultSet
                 mock_backend = Mock(spec=ThriftDatabricksClient)

tests/unit/test_sea_backend.py

@@ -621,18 +621,6 @@ def test_utility_methods(self, sea_client):
         assert description[1][1] == "INT"  # type_code
         assert description[1][6] is False  # null_ok
 
-        # Test _extract_description_from_manifest with empty columns
-        empty_manifest = MagicMock()
-        empty_manifest.schema = {"columns": []}
-        assert sea_client._extract_description_from_manifest(empty_manifest) is None
-
-        # Test _extract_description_from_manifest with no columns key
-        no_columns_manifest = MagicMock()
-        no_columns_manifest.schema = {}
-        assert (
-            sea_client._extract_description_from_manifest(no_columns_manifest) is None
-        )
-
     def test_results_message_to_execute_response_is_staging_operation(self, sea_client):
         """Test that is_staging_operation is correctly set from manifest.is_volume_operation."""
         # Test when is_volume_operation is True