Fix schema recognition of struct field types (googleapis#9001)

* Fix schema recognition of struct field types

A struct field can be referred to as "RECORD" or "STRUCT", and this
commit assures that the to_api_repr() logic is correct.

* Mark STRUCT_TYPES as private in schema.py

bigquery/google/cloud/bigquery/_pandas_helpers.py

@@ -47,7 +47,6 @@
     "please install google-cloud-bigquery-storage to use bqstorage features."
 )
 
-STRUCT_TYPES = ("RECORD", "STRUCT")
 _PROGRESS_INTERVAL = 0.2  # Maximum time between download status checks, in seconds.
 
 
@@ -126,7 +125,7 @@ def bq_to_arrow_data_type(field):
             return pyarrow.list_(inner_type)
         return None
 
-    if field.field_type.upper() in STRUCT_TYPES:
+    if field.field_type.upper() in schema._STRUCT_TYPES:
         return bq_to_arrow_struct_data_type(field)
 
     data_type_constructor = BQ_TO_ARROW_SCALARS.get(field.field_type.upper())
@@ -168,7 +167,7 @@ def bq_to_arrow_array(series, bq_field):
     arrow_type = bq_to_arrow_data_type(bq_field)
     if bq_field.mode.upper() == "REPEATED":
         return pyarrow.ListArray.from_pandas(series, type=arrow_type)
-    if bq_field.field_type.upper() in STRUCT_TYPES:
+    if bq_field.field_type.upper() in schema._STRUCT_TYPES:
         return pyarrow.StructArray.from_pandas(series, type=arrow_type)
     return pyarrow.array(series, type=arrow_type)
 

bigquery/google/cloud/bigquery/schema.py

@@ -17,6 +17,8 @@
 from google.cloud.bigquery_v2 import types
 
 
+_STRUCT_TYPES = ("RECORD", "STRUCT")
+
 # SQL types reference:
 # https://cloud.google.com/bigquery/data-types#legacy_sql_data_types
 # https://cloud.google.com/bigquery/docs/reference/standard-sql/data-types
@@ -150,7 +152,7 @@ def to_api_repr(self):
 
         # If this is a RECORD type, then sub-fields are also included,
         # add this to the serialized representation.
-        if self.field_type.upper() == "RECORD":
+        if self.field_type.upper() in _STRUCT_TYPES:
             answer["fields"] = [f.to_api_repr() for f in self.fields]
 
         # Done; return the serialized dictionary.

bigquery/tests/unit/test_schema.py

@@ -71,25 +71,26 @@ def test_to_api_repr(self):
         )
 
     def test_to_api_repr_with_subfield(self):
-        subfield = self._make_one("bar", "INTEGER", "NULLABLE")
-        field = self._make_one("foo", "RECORD", "REQUIRED", fields=(subfield,))
-        self.assertEqual(
-            field.to_api_repr(),
-            {
-                "fields": [
-                    {
-                        "mode": "NULLABLE",
-                        "name": "bar",
-                        "type": "INTEGER",
-                        "description": None,
-                    }
-                ],
-                "mode": "REQUIRED",
-                "name": "foo",
-                "type": "RECORD",
-                "description": None,
-            },
-        )
+        for record_type in ("RECORD", "STRUCT"):
+            subfield = self._make_one("bar", "INTEGER", "NULLABLE")
+            field = self._make_one("foo", record_type, "REQUIRED", fields=(subfield,))
+            self.assertEqual(
+                field.to_api_repr(),
+                {
+                    "fields": [
+                        {
+                            "mode": "NULLABLE",
+                            "name": "bar",
+                            "type": "INTEGER",
+                            "description": None,
+                        }
+                    ],
+                    "mode": "REQUIRED",
+                    "name": "foo",
+                    "type": record_type,
+                    "description": None,
+                },
+            )
 
     def test_from_api_repr(self):
         field = self._get_target_class().from_api_repr(