feat: preserve unknown fields from the REST API representaton in SchemaField

Author: tswast

google/cloud/bigquery/schema.py

@@ -203,8 +203,8 @@ def __init__(
             self._properties["rangeElementType"] = {"type": range_element_type}
         if isinstance(range_element_type, FieldElementType):
             self._properties["rangeElementType"] = range_element_type.to_api_repr()
-
-        self._fields = tuple(fields)
+        if fields:  # Don't set the property if it's not set.
+            self._properties["fields"] = [field.to_api_repr() for field in fields]
 
     @staticmethod
     def __get_int(api_repr, name):
@@ -225,43 +225,19 @@ def from_api_repr(cls, api_repr: dict) -> "SchemaField":
         Returns:
             google.cloud.bigquery.schema.SchemaField: The ``SchemaField`` object.
         """
-        field_type = api_repr["type"].upper()
-
-        # Handle optional properties with default values
-        mode = api_repr.get("mode", "NULLABLE")
-        description = api_repr.get("description", _DEFAULT_VALUE)
-        fields = api_repr.get("fields", ())
-        policy_tags = api_repr.get("policyTags", _DEFAULT_VALUE)
+        placeholder = cls("this_will_be_replaced", "PLACEHOLDER")
 
-        default_value_expression = api_repr.get("defaultValueExpression", None)
+        # Note: we don't make a copy of api_repr because this can cause
+        # unnecessary slowdowns, especially on deeply nested STRUCT / RECORD
+        # fields. See https://github.com/googleapis/python-bigquery/issues/6
+        placeholder._properties = api_repr
 
-        if policy_tags is not None and policy_tags is not _DEFAULT_VALUE:
-            policy_tags = PolicyTagList.from_api_repr(policy_tags)
-
-        if api_repr.get("rangeElementType"):
-            range_element_type = cast(dict, api_repr.get("rangeElementType"))
-            element_type = range_element_type.get("type")
-        else:
-            element_type = None
-
-        return cls(
-            field_type=field_type,
-            fields=[cls.from_api_repr(f) for f in fields],
-            mode=mode.upper(),
-            default_value_expression=default_value_expression,
-            description=description,
-            name=api_repr["name"],
-            policy_tags=policy_tags,
-            precision=cls.__get_int(api_repr, "precision"),
-            scale=cls.__get_int(api_repr, "scale"),
-            max_length=cls.__get_int(api_repr, "maxLength"),
-            range_element_type=element_type,
-        )
+        return placeholder
 
     @property
     def name(self):
         """str: The name of the field."""
-        return self._properties["name"]
+        return self._properties.get("name", "")
 
     @property
     def field_type(self):
@@ -270,7 +246,10 @@ def field_type(self):
         See:
         https://cloud.google.com/bigquery/docs/reference/rest/v2/tables#TableFieldSchema.FIELDS.type
         """
-        return self._properties["type"]
+        type_ = self._properties.get("type")
+        if type_ is None:  # Shouldn't happen, but some unit tests do this.
+            return None
+        return type_.upper()
 
     @property
     def mode(self):
@@ -279,7 +258,7 @@ def mode(self):
         See:
         https://cloud.google.com/bigquery/docs/reference/rest/v2/tables#TableFieldSchema.FIELDS.mode
         """
-        return self._properties.get("mode")
+        return self._properties.get("mode", "NULLABLE").upper()
 
     @property
     def is_nullable(self):
@@ -329,7 +308,7 @@ def fields(self):
 
         Must be empty unset if ``field_type`` is not 'RECORD'.
         """
-        return self._fields
+        return tuple(_to_schema_fields(self._properties.get("fields", [])))
 
     @property
     def policy_tags(self):
@@ -345,14 +324,10 @@ def to_api_repr(self) -> dict:
         Returns:
             Dict: A dictionary representing the SchemaField in a serialized form.
         """
-        answer = self._properties.copy()
-
-        # If this is a RECORD type, then sub-fields are also included,
-        # add this to the serialized representation.
-        if self.field_type.upper() in _STRUCT_TYPES:
-            answer["fields"] = [f.to_api_repr() for f in self.fields]
-
-        # Done; return the serialized dictionary.
+        # Note: we don't make a copy of _properties because this can cause
+        # unnecessary slowdowns, especially on deeply nested STRUCT / RECORD
+        # fields. See https://github.com/googleapis/python-bigquery/issues/6
+        answer = self._properties
         return answer
 
     def _key(self):
@@ -389,7 +364,7 @@ def _key(self):
             self.mode.upper(),  # pytype: disable=attribute-error
             self.default_value_expression,
             self.description,
-            self._fields,
+            self.fields,
             policy_tags,
         )
 

tests/unit/job/test_load_config.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import copy
 import warnings
 
 import pytest
@@ -571,16 +572,34 @@ def test_schema_setter_valid_mappings_list(self):
             config._properties["load"]["schema"], {"fields": [full_name_repr, age_repr]}
         )
 
-    def test_schema_setter_invalid_mappings_list(self):
+    def test_schema_setter_allows_unknown_properties(self):
         config = self._get_target_class()()
 
         schema = [
-            {"name": "full_name", "type": "STRING", "mode": "REQUIRED"},
-            {"name": "age", "typeoo": "INTEGER", "mode": "REQUIRED"},
+            {
+                "name": "full_name",
+                "type": "STRING",
+                "mode": "REQUIRED",
+                "someNewProperty": "test-value",
+            },
+            {
+                "name": "age",
+                # Note: This type should be included, too. Avoid client-side
+                # validation, as it could prevent backwards-compatible
+                # evolution of the server-side behavior.
+                "typo": "INTEGER",
+                "mode": "REQUIRED",
+                "anotherNewProperty": "another-test",
+            },
         ]
 
-        with self.assertRaises(Exception):
-            config.schema = schema
+        # Make sure the setter doesn't mutate schema.
+        expected_schema = copy.deepcopy(schema)
+
+        config.schema = schema
+
+        # _properties should include all fields, including unknown ones.
+        assert config._properties["load"]["schema"]["fields"] == expected_schema
 
     def test_schema_setter_unsetting_schema(self):
         from google.cloud.bigquery.schema import SchemaField

tests/unit/test_schema.py

@@ -12,14 +12,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from google.cloud import bigquery
-from google.cloud.bigquery.standard_sql import StandardSqlStructType
-from google.cloud.bigquery.schema import PolicyTagList
+import copy
 import unittest
 from unittest import mock
 
 import pytest
 
+from google.cloud import bigquery
+from google.cloud.bigquery.standard_sql import StandardSqlStructType
+from google.cloud.bigquery.schema import PolicyTagList
+
 
 class TestSchemaField(unittest.TestCase):
     @staticmethod
@@ -821,13 +823,32 @@ def test_schema_fields_sequence(self):
         result = self._call_fut(schema)
         self.assertEqual(result, schema)
 
-    def test_invalid_mapping_representation(self):
+    def test_unknown_properties(self):
         schema = [
-            {"name": "full_name", "type": "STRING", "mode": "REQUIRED"},
-            {"name": "address", "typeooo": "STRING", "mode": "REQUIRED"},
+            {
+                "name": "full_name",
+                "type": "STRING",
+                "mode": "REQUIRED",
+                "someNewProperty": "test-value",
+            },
+            {
+                "name": "age",
+                # Note: This type should be included, too. Avoid client-side
+                # validation, as it could prevent backwards-compatible
+                # evolution of the server-side behavior.
+                "typo": "INTEGER",
+                "mode": "REQUIRED",
+                "anotherNewProperty": "another-test",
+            },
         ]
-        with self.assertRaises(Exception):
-            self._call_fut(schema)
+        
+        # Make sure the setter doesn't mutate schema.
+        expected_schema = copy.deepcopy(schema)
+
+        result = self._call_fut(schema)
+
+        for api_repr, field in zip(expected_schema, result):
+            assert field.to_api_repr() == api_repr
 
     def test_valid_mapping_representation(self):
         from google.cloud.bigquery.schema import SchemaField

tests/unit/test_table.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import copy
 import datetime
 import logging
 import re
@@ -711,14 +712,35 @@ def test_schema_setter_valid_fields(self):
         table.schema = [full_name, age]
         self.assertEqual(table.schema, [full_name, age])
 
-    def test_schema_setter_invalid_mapping_representation(self):
+    def test_schema_setter_allows_unknown_properties(self):
         dataset = DatasetReference(self.PROJECT, self.DS_ID)
         table_ref = dataset.table(self.TABLE_NAME)
         table = self._make_one(table_ref)
-        full_name = {"name": "full_name", "type": "STRING", "mode": "REQUIRED"}
-        invalid_field = {"name": "full_name", "typeooo": "STRING", "mode": "REQUIRED"}
-        with self.assertRaises(Exception):
-            table.schema = [full_name, invalid_field]
+        schema = [
+            {
+                "name": "full_name",
+                "type": "STRING",
+                "mode": "REQUIRED",
+                "someNewProperty": "test-value",
+            },
+            {
+                "name": "age",
+                # Note: This type should be included, too. Avoid client-side
+                # validation, as it could prevent backwards-compatible
+                # evolution of the server-side behavior.
+                "typo": "INTEGER",
+                "mode": "REQUIRED",
+                "anotherNewProperty": "another-test",
+            },
+        ]
+        
+        # Make sure the setter doesn't mutate schema.
+        expected_schema = copy.deepcopy(schema)
+        
+        table.schema = schema
+        
+        # _properties should include all fields, including unknown ones.
+        assert table._properties["schema"]["fields"] == expected_schema
 
     def test_schema_setter_valid_mapping_representation(self):
         from google.cloud.bigquery.schema import SchemaField