Merge pull request marshmallow-code#1188 from marshmallow-code/remove…

…-container-attribute

Remove special-casing for accessing attributes of objects in a list

CHANGELOG.rst

@@ -1,6 +1,15 @@
 Changelog
 ---------
 
+3.0.0 (unreleased)
+++++++++++++++++++
+
+Other changes:
+
+- *Backwards-incompatible*: Remove special-casing in ``fields.List`` and
+  ``fields.Tuple`` for accessing nested attributes (:pr:`1188`).
+  Use ``fields.List(fields.Pluck(...))`` instead.
+
 3.0.0rc5 (2019-03-30)
 +++++++++++++++++++++
 

docs/upgrading.rst

@@ -659,6 +659,24 @@ In marshmallow 2.x, when a string was passed to a ``Nested`` field's ```only`` p
         name = fields.Str()
         friends = fields.Pluck('self', 'name', many=True)
 
+
+Accessing attributes on objects within a list
+*********************************************
+
+In order to serialize attributes on inner objects within a list, use the
+``Pluck`` field.
+
+.. code-block:: python
+
+    # 2.x
+    class FactorySchema(Schema):
+        widget_ids = fields.List(fields.Int(attribute='id'))
+
+    # 3.x
+    class FactorySchema(Schema):
+        widget_ids = fields.List(fields.Pluck(WidgetSchema, 'id'))
+
+
 ``Float`` field takes a new ``allow_nan`` parameter
 ***************************************************
 

src/marshmallow/fields.py

@@ -580,18 +580,6 @@ def __init__(self, cls_or_instance, **kwargs):
                 'marshmallow.base.FieldABC.',
             )
 
-    def get_value(self, obj, attr, accessor=None):
-        """Return the value for a given key from an object."""
-        value = super(List, self).get_value(obj, attr, accessor=accessor)
-        if self.container.attribute:
-            if utils.is_collection(value):
-                return [
-                    self.container.get_value(each, self.container.attribute)
-                    for each in value
-                ]
-            return self.container.get_value(value, self.container.attribute)
-        return value
-
     def _bind_to_schema(self, field_name, schema):
         super(List, self)._bind_to_schema(field_name, schema)
         self.container = copy.deepcopy(self.container)
@@ -677,21 +665,6 @@ def _bind_to_schema(self, field_name, schema):
             new_tuple_fields.append(new_container)
         self.tuple_fields = new_tuple_fields
 
-    def get_value(self, obj, attr, accessor=None):
-        """Return the value for a given key from an object."""
-        value = super(Tuple, self).get_value(obj, attr, accessor=accessor)
-        if any(container.attribute for container in self.tuple_fields):
-            if not utils.is_collection(value):
-                self.fail('invalid')
-            result = []
-            for container, each in zip(self.tuple_fields, value):
-                if container.attribute is None:
-                    result.append(each)
-                else:
-                    result.append(container.get_value(each, container.attribute))
-            return tuple(result)
-        return value
-
     def _serialize(self, value, attr, obj, **kwargs):
         if value is None:
             return None

tests/test_serialization.py

@@ -712,18 +712,6 @@ def test_list_field_serialize_none_returns_none(self):
         field = fields.List(fields.DateTime)
         assert field.serialize('dtimes', obj) is None
 
-    def test_list_field_respect_inner_attribute(self):
-        now = dt.datetime.now()
-        obj = DateTimeList([now])
-        field = fields.List(fields.Int(attribute='day'))
-        assert field.serialize('dtimes', obj) == [now.day]
-
-    def test_list_field_respect_inner_attribute_single_value(self):
-        now = dt.datetime.now()
-        obj = DateTimeList(now)
-        field = fields.List(fields.Int(attribute='day'))
-        assert field.serialize('dtimes', obj) == [now.day]
-
     def test_list_field_work_with_generator_single_value(self):
         def custom_generator():
             yield dt.datetime.utcnow()
@@ -826,12 +814,6 @@ def test_tuple_field_serialize_none_returns_none(self):
         field = fields.Tuple([fields.DateTime, fields.Integer])
         assert field.serialize('dtime_int', obj) is None
 
-    def test_tuple_field_respect_inner_attribute(self):
-        now = dt.datetime.now()
-        obj = DateTimeIntegerTuple((now, 42))
-        field = fields.Tuple([fields.Int(attribute='day'), fields.Integer])
-        assert field.serialize('dtime_int', obj) == (now.day, 42)
-
     def test_bad_tuple_field(self):
         class ASchema(Schema):
             id = fields.Int()