Let attribute default to field name

Author: lafrech

src/marshmallow/fields.py

@@ -378,6 +378,7 @@ def _bind_to_schema(self, field_name, schema):
         self.parent = self.parent or schema
         self.name = self.name or field_name
         self.data_key = self.data_key if self.data_key is not None else field_name
+        self.attribute = self.attribute if self.attribute is not None else field_name
         self.root = self.root or (
             self.parent.root if isinstance(self.parent, FieldABC) else self.parent
         )

src/marshmallow/schema.py

@@ -663,7 +663,7 @@ def _deserialize(
                     index=index,
                 )
                 if value is not missing:
-                    key = field_obj.attribute or attr_name
+                    key = field_obj.attribute
                     set_value(ret_d, key, value)
             if unknown != EXCLUDE:
                 fields = {field_obj.data_key for field_obj in self.load_fields.values()}
@@ -991,7 +991,7 @@ def _init_fields(self) -> None:
                 "Check the following field names and "
                 "data_key arguments: {}".format(list(data_keys_duplicates))
             )
-        load_attributes = [obj.attribute or name for name, obj in load_fields.items()]
+        load_attributes = [obj.attribute for obj in load_fields.values()]
         if len(load_attributes) != len(set(load_attributes)):
             attributes_duplicates = {
                 x for x in load_attributes if load_attributes.count(x) > 1
@@ -1105,7 +1105,7 @@ def _invoke_field_validators(self, *, error_store: ErrorStore, data, many: bool)
             if many:
                 for idx, item in enumerate(data):
                     try:
-                        value = item[field_obj.attribute or field_name]
+                        value = item[field_obj.attribute]
                     except KeyError:
                         pass
                     else:
@@ -1120,7 +1120,7 @@ def _invoke_field_validators(self, *, error_store: ErrorStore, data, many: bool)
                             data[idx].pop(field_name, None)
             else:
                 try:
-                    value = data[field_obj.attribute or field_name]
+                    value = data[field_obj.attribute]
                 except KeyError:
                     pass
                 else:

tests/test_fields.py

@@ -101,6 +101,15 @@ class MySchema(Schema):
         assert schema_fields["field_1"].data_key == "field_one"
         assert schema_fields["field_2"].data_key == "field_2"
 
+    def test_attribute_defaults_to_field_name(self):
+        class MySchema(Schema):
+            field_1 = fields.String(attribute="field_one")
+            field_2 = fields.String()
+
+        schema_fields = MySchema().fields
+        assert schema_fields["field_1"].attribute == "field_one"
+        assert schema_fields["field_2"].attribute == "field_2"
+
 
 class TestParentAndName:
     class MySchema(Schema):