fix(dtypes): Propagate description in convert_to_schema_field for lists

Author: shuoweil

bigframes/dtypes.py

@@ -822,7 +822,11 @@ def convert_to_schema_field(
             )
             inner_field = convert_to_schema_field(name, inner_type, overrides)
             return google.cloud.bigquery.SchemaField(
-                name, inner_field.field_type, mode="REPEATED", fields=inner_field.fields
+                name,
+                inner_field.field_type,
+                mode="REPEATED",
+                fields=inner_field.fields,
+                description=inner_field.description,
             )
         if pa.types.is_struct(bigframes_dtype.pyarrow_dtype):
             inner_fields: list[google.cloud.bigquery.SchemaField] = []

tests/unit/test_dtypes.py

@@ -71,3 +71,11 @@ def test_infer_literal_type_arrow_scalar(scalar, expected_dtype):
 )
 def test_contains_db_dtypes_json_arrow_type(type_, expected):
     assert bigframes.dtypes.contains_db_dtypes_json_arrow_type(type_) == expected
+
+
+def test_convert_to_schema_field_list_description():
+    bf_dtype = bigframes.dtypes.OBJ_REF_DTYPE
+    list_bf_dtype = bigframes.dtypes.list_type(bf_dtype)
+    field = bigframes.dtypes.convert_to_schema_field("my_list", list_bf_dtype)
+    assert field.description == "bigframes_dtype: OBJ_REF_DTYPE"
+    assert field.mode == "REPEATED"