adds support for fields with local dataclass types & test

mashumaro/core/meta/code/builder.py

@@ -80,6 +80,8 @@
 __POST_SERIALIZE__ = "__post_serialize__"
 __POST_DESERIALIZE__ = "__post_deserialize__"
 
+_LOCALS_TYPE_VAR = "__locals_type_var__"
+
 
 class InternalMethodName(str):
     _PREFIX = "__mashumaro_"
@@ -303,7 +305,9 @@ def compile(self) -> None:
             else:
                 print(f"{type_name(self.cls)}:")
             print(code)
-        exec(code, self.globals, self.__dict__)
+
+        localns = {**self.__dict__, _LOCALS_TYPE_VAR: self.cls}
+        exec(code, self.globals, localns)
 
     def evaluate_forward_ref(
         self,
@@ -555,6 +559,10 @@ def _unpack_method_set_value(
             ftype,
             resolved_type_params=self.get_field_resolved_type_params(fname),
         )
+
+        if "<locals>" in field_type:
+            field_type = _LOCALS_TYPE_VAR
+
         could_be_none = (
             ftype in (typing.Any, type(None), None)
             or is_type_var_any(self._get_real_type(fname, ftype))

tests/test_common.py

@@ -262,3 +262,17 @@ def test_kw_args_when_pos_arg_is_overridden_with_field():
     assert loaded.pos2 == 2
     assert loaded.pos3 == 3
     assert loaded.kw1 == 4
+
+
+def test_local_type():
+    @dataclass
+    class LocalType:
+        pass
+
+    @dataclass
+    class DataClassWithLocalType(DataClassDictMixin):
+        x: LocalType
+
+    obj = DataClassWithLocalType(LocalType())
+    assert obj.to_dict() == {"x": {}}
+    assert DataClassWithLocalType.from_dict({"x": {}}) == obj