fix: avoid RecursionError when using some types like Enum or Literal with generic models

changes/2436-PrettyWood.md

@@ -0,0 +1 @@
+Support properly `Enum` when combined with generic models

pydantic/generics.py

@@ -1,5 +1,6 @@
 import sys
 import typing
+from enum import Enum
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -211,7 +212,7 @@ def iter_contained_typevars(v: Any) -> Iterator[TypeVarType]:
         yield v
     elif hasattr(v, '__parameters__') and not get_origin(v) and lenient_issubclass(v, GenericModel):
         yield from v.__parameters__
-    elif isinstance(v, Iterable):
+    elif isinstance(v, Iterable) and not lenient_issubclass(v, Enum):
         for var in v:
             yield from iter_contained_typevars(var)
     else:

tests/test_generics.py

@@ -1039,3 +1039,21 @@ class Model2(GenericModel, Generic[T]):
     Model2 = module.Model2
     result = Model1[str].parse_obj(dict(ref=dict(ref=dict(ref=dict(ref=123)))))
     assert result == Model1(ref=Model2(ref=Model1(ref=Model2(ref='123'))))
+
+
+@skip_36
+def test_generic_enum():
+    T = TypeVar('T')
+
+    class SomeGenericModel(GenericModel, Generic[T]):
+        some_field: T
+
+    class SomeStringEnum(str, Enum):
+        A = 'A'
+        B = 'B'
+
+    class MyModel(BaseModel):
+        my_gen: SomeGenericModel[SomeStringEnum]
+
+    m = MyModel.parse_obj({'my_gen': {'some_field': 'A'}})
+    assert m.my_gen.some_field is SomeStringEnum.A