marshmallow-code#1993 Fix serialization of List items if they are ser…

…ialized by fields.Method.

AUTHORS.rst

@@ -169,3 +169,4 @@ Contributors (chronological)
 - Kevin Kirsche `@kkirsche <https://github.com/kkirsche>`_
 - Isira Seneviratne `@Isira-Seneviratne <https://github.com/Isira-Seneviratne>`_
 - Karthikeyan Singaravelan `@tirkarthi  <https://github.com/tirkarthi>`_
+- Benedek Horváth `@benedekh <https://github.com/benedekh>`_

src/marshmallow/fields.py

@@ -763,7 +763,8 @@ def __init__(self, cls_or_instance: Field | type, **kwargs):
     def _bind_to_schema(self, field_name, schema):
         super()._bind_to_schema(field_name, schema)
         self.inner = copy.deepcopy(self.inner)
-        self.inner._bind_to_schema(field_name, self)
+        self.inner.parent = self
+        self.inner._bind_to_schema(field_name, schema)
         if isinstance(self.inner, Nested):
             self.inner.only = self.only
             self.inner.exclude = self.exclude

tests/test_fields.py

@@ -665,3 +665,16 @@ class Family(Schema):
                     "daughter": {"value": {"age": ["Missing data for required field."]}}
                 }
             }
+
+
+class TestMethodSerializationOfListItems:
+    def test_method_serialization_of_list_items(self):
+        class ExampleSchema(Schema):
+            dummy_list = fields.List(fields.Method(serialize="serialize_me"))
+
+            def serialize_me(self, obj):
+                return [str(value) for value in obj["dummy_list"]]
+
+        obj = {"dummy_list": ["hello", "world"]}
+        dumped = ExampleSchema().dump(obj)
+        assert dumped == {"dummy_list": [["hello", "world"], ["hello", "world"]]}