fix unit tests

Author: tswast

bigframes/core/backports.py

@@ -0,0 +1,33 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Helpers for working across versions of different depenencies."""
+
+from typing import List
+
+import pyarrow
+
+
+def pyarrow_struct_type_fields(struct_type: pyarrow.StructType) -> List[pyarrow.Field]:
+    """StructType.fields was added in pyarrow 18.
+
+    See: https://arrow.apache.org/docs/18.0/python/generated/pyarrow.StructType.html
+    """
+
+    if hasattr(struct_type, "fields"):
+        return struct_type.fields
+
+    return [
+        struct_type.field(field_index) for field_index in range(struct_type.num_fields)
+    ]

bigframes/dtypes.py

@@ -31,6 +31,7 @@
 import pyarrow as pa
 import shapely.geometry  # type: ignore
 
+import bigframes.core.backports
 import bigframes.exceptions
 
 # Type hints for Pandas dtypes supported by BigQuery DataFrame
@@ -372,8 +373,7 @@ def get_struct_fields(type_: ExpressionType) -> dict[str, Dtype]:
     assert isinstance(type_.pyarrow_dtype, pa.StructType)
     struct_type = type_.pyarrow_dtype
     result: dict[str, Dtype] = {}
-    for field_no in range(struct_type.num_fields):
-        field = struct_type.field(field_no)
+    for field in bigframes.core.backports.pyarrow_struct_type_fields(struct_type):
         result[field.name] = arrow_dtype_to_bigframes_dtype(field.type)
     return result
 
@@ -551,7 +551,8 @@ def arrow_type_to_literal(
         return [arrow_type_to_literal(arrow_type.value_type)]
     if pa.types.is_struct(arrow_type):
         return {
-            field.name: arrow_type_to_literal(field.type) for field in arrow_type.fields
+            field.name: arrow_type_to_literal(field.type)
+            for field in bigframes.core.backports.pyarrow_struct_type_fields(arrow_type)
         }
     if pa.types.is_string(arrow_type):
         return "string"
@@ -930,7 +931,8 @@ def contains_db_dtypes_json_arrow_type(type_):
 
     if isinstance(type_, pa.StructType):
         return any(
-            contains_db_dtypes_json_arrow_type(field.type) for field in type_.fields
+            contains_db_dtypes_json_arrow_type(field.type)
+            for field in bigframes.core.backports.pyarrow_struct_type_fields(type_)
         )
     return False