Fix accessing builtin dict's attrs for a missing field

Author: mahenzon

AUTHORS.rst

@@ -99,7 +99,7 @@ Contributors (chronological)
 - Harlov Nikita `@harlov <https://github.com/harlov>`_
 - `@stj <https://github.com/stj>`_
 - Tomasz Magulski `@magul <https://github.com/magul>`_
-- Suren Khorenyan `@surik00 <https://github.com/surik00>`_
+- Suren Khorenyan `@mahenzon <https://github.com/mahenzon>`_
 - Jeffrey Berger `@JeffBerger <https://github.com/JeffBerger>`_
 - Felix Yan `@felixonmars <https://github.com/felixonmars>`_
 - Prasanjit Prakash `@ikilledthecat <https://github.com/ikilledthecat>`_

src/marshmallow/utils.py

@@ -242,7 +242,9 @@ def _get_value_for_key(obj, key, default):
 
     try:
         return obj[key]
-    except (KeyError, IndexError, TypeError, AttributeError):
+    except (KeyError, IndexError, TypeError, AttributeError) as e:
+        if isinstance(e, KeyError) and type(obj) is dict:
+            return default
         return getattr(obj, key, default)
 
 

tests/test_serialization.py

@@ -800,3 +800,23 @@ def gen():
     data = OtherSchema().dump(obj)
 
     assert data.get("objects") == [{"name": "foo"}, {"name": "bar"}]
+
+
+def test_missing_update_field_in_dict_processed_properly():
+    """
+    Checking case when a schema has 'update' field
+    and the object to be dumped is a dict
+    and the value for this field is missing
+
+    https://github.com/marshmallow-code/marshmallow/pull/1557
+    :return:
+    """
+
+    class MySchema(Schema):
+        update = fields.Boolean(required=False)
+
+    schema = MySchema()
+    data = schema.dump({})
+    assert data == {}
+    data = schema.dump({"update": True})
+    assert data == {"update": True}