Modify Nested field to handle the combination of many=True and allow_…

…none=True marshmallow-code#1497

AUTHORS.rst

@@ -143,3 +143,4 @@ Contributors (chronological)
 - Taneli Hukkinen `@hukkinj1 <https://github.com/hukkinj1>`_
 - `@Reskov <https://github.com/Reskov>`_
 - Albert Tugushev `@atugushev <https://github.com/atugushev>`_
+- Jonathan Gayvallet `@Meallia <https://github.com/Meallia>`_

src/marshmallow/fields.py

@@ -577,6 +577,13 @@ def _serialize(self, nested_obj, attr, obj, many=False, **kwargs):
         if nested_obj is None:
             return None
         many = schema.many or self.many or many
+        if many and self.allow_none:
+            ret = schema.dump(
+                [obj for obj in nested_obj if obj is not None], many=self.many or many
+            )
+            for none_index in (i for i, obj in enumerate(nested_obj) if obj is None):
+                ret.insert(none_index, None)
+            return ret
         return schema.dump(nested_obj, many=self.many or many)
 
     def _test_collection(self, value, many=False):
@@ -587,9 +594,19 @@ def _test_collection(self, value, many=False):
     def _load(self, value, data, partial=None, many=False):
         many = self.schema.many or self.many or many
         try:
-            valid_data = self.schema.load(
-                value, unknown=self.unknown, partial=partial, many=many
-            )
+            if many and self.allow_none:
+                valid_data = self.schema.load(
+                    [obj for obj in value if obj is not None],
+                    unknown=self.unknown,
+                    partial=partial,
+                    many=many,
+                )
+                for none_index in (i for i, obj in enumerate(value) if obj is None):
+                    valid_data.insert(none_index, None)
+            else:
+                valid_data = self.schema.load(
+                    value, unknown=self.unknown, partial=partial, many=many
+                )
         except ValidationError as error:
             raise ValidationError(
                 error.messages, valid_data=error.valid_data

tests/test_deserialization.py

@@ -16,7 +16,7 @@ class TestDeserializingNone:
     @pytest.mark.parametrize("FieldClass", ALL_FIELDS)
     def test_fields_allow_none_deserialize_to_none(self, FieldClass):
         field = FieldClass(allow_none=True)
-        field.deserialize(None) is None
+        assert field.deserialize(None) is None
 
     # https://github.com/marshmallow-code/marshmallow/issues/111
     @pytest.mark.parametrize("FieldClass", ALL_FIELDS)
@@ -28,7 +28,7 @@ def test_fields_dont_allow_none_by_default(self, FieldClass):
     def test_allow_none_is_true_if_missing_is_true(self):
         field = fields.Field(missing=None)
         assert field.allow_none is True
-        field.deserialize(None) is None
+        assert field.deserialize(None) is None
 
     def test_list_field_deserialize_none_to_none(self):
         field = fields.List(fields.String(allow_none=True), allow_none=True)
@@ -38,6 +38,24 @@ def test_tuple_field_deserialize_none_to_none(self):
         field = fields.Tuple([fields.String()], allow_none=True)
         assert field.deserialize(None) is None
 
+    def test_list_of_nested_nullable_deserialize_none_to_none(self):
+        field = fields.List(fields.Nested(Schema(), allow_none=True))
+        assert field.deserialize([None, {}]) == [None, {}]
+
+    def test_nested_multiple_nullable_deserialize_none_to_none(self):
+        field = fields.Nested(Schema(), allow_none=True, many=True)
+        assert field.deserialize([None, {}]) == [None, {}]
+
+    def test_list_of_nested_non_nullable_deserialize_none_to_validation_error(self):
+        field = fields.List(fields.Nested(Schema(), allow_none=False))
+        with pytest.raises(ValidationError):
+            field.deserialize([None])
+
+    def test_nested_multiple_non_nullable_deserialize_none_to_validation_error(self):
+        field = fields.Nested(Schema(), allow_none=True, many=False)
+        with pytest.raises(ValidationError):
+            field.deserialize([None])
+
 
 class TestFieldDeserialization:
     def test_float_field_deserialization(self):

tests/test_serialization.py

@@ -727,6 +727,18 @@ def test_all_fields_serialize_none_to_none(self, FieldClass):
         res = field.serialize("foo", {"foo": None})
         assert res is None
 
+    def test_list_of_nested_nullable_serialize_none_to_none(self):
+        res = fields.List(fields.Nested(Schema(), allow_none=True)).serialize(
+            "foo", {"foo": [None, {}]}
+        )
+        assert res == [None, {}]
+
+    def test_nested_multiple_nullable_serialize_none_to_none(self):
+        res = fields.Nested(Schema(), allow_none=True, many=True).serialize(
+            "foo", {"foo": [None, {}]}
+        )
+        assert res == [None, {}]
+
 
 class TestSchemaSerialization:
     def test_serialize_with_missing_param_value(self):