Fix type vars order when Generic is in bases

Author: Fatal1ty

mashumaro/core/meta/helpers.py

@@ -551,11 +551,17 @@ def resolve_type_params(
     result = {typ: resolved_type_params}
     type_params = []
 
+    # According to the docs, if Generic[...] is present, then the order
+    # of variables is always determined by their order in Generic[...]
     for base in get_orig_bases(typ):
-        base_type_params = collect_type_params(base)
-        for type_param in base_type_params:
-            if type_param not in type_params:
-                type_params.append(type_param)
+        if get_type_origin(base) is typing.Generic:
+            type_params = list(collect_type_params(base))
+    if not type_params:
+        for base in get_orig_bases(typ):
+            base_type_params = collect_type_params(base)
+            for type_param in base_type_params:
+                if type_param not in type_params:
+                    type_params.append(type_param)
 
     _check_generic(typ, type_params, type_args)
 

tests/test_generics.py

@@ -11,6 +11,7 @@
 
 T = TypeVar("T")
 S = TypeVar("S")
+K = TypeVar("K")
 P = TypeVar("P", Mapping[int, int], List[float])
 
 
@@ -279,3 +280,25 @@ class Config(BaseConfig):
         fieldD=A(field=1.2), fieldC=B(fieldB=A(field=2)), fieldB=A(field=2)
     )
     assert D.from_dict(obj.to_dict()) == obj
+
+
+def test_vars_order_when_generic_presented_in_bases() -> None:
+    @dataclass
+    class Base(DataClassDictMixin, Generic[T]):
+        kind: str = "base"
+
+    class NotSerializable:
+        pass
+
+    @dataclass
+    class Extended(Base[K], Generic[S, K]):
+        payload: S | None = None
+
+    @dataclass
+    class Sub(Extended[Base, NotSerializable]):
+        pass
+
+    assert Sub(payload=Base()).to_dict() == {
+        "kind": "base",
+        "payload": {"kind": "base"},
+    }

tests/test_generics_pep_695.py

@@ -259,3 +259,25 @@ def test_generic_serializable_type_getitem():
     class DataClass(DataClassDictMixin):
         # Simply specializing the type would lead to an AttributeError.
         x: GenericSerializableType[int]
+
+
+def test_vars_order_when_generic_presented_in_bases_pep_695() -> None:
+    @dataclass
+    class Base[T](DataClassDictMixin):
+        kind: str = "base"
+
+    class NotSerializable:
+        pass
+
+    @dataclass
+    class Extended[S: Base, K](Base[K]):
+        payload: S | None = None
+
+    @dataclass
+    class Sub(Extended[Base, NotSerializable]):
+        pass
+
+    assert Sub(payload=Base()).to_dict() == {
+        "kind": "base",
+        "payload": {"kind": "base"},
+    }