Fix inheritance support for msgspec (litestar-org#295)

* fix inherited models support for msgspec

* use `get_type_hints`

polyfactory/factories/msgspec_factory.py

@@ -10,6 +10,8 @@
     cast,
 )
 
+from typing_extensions import get_type_hints
+
 from polyfactory.exceptions import MissingDependencyException
 from polyfactory.factories.base import BaseFactory
 from polyfactory.field_meta import FieldMeta, Null
@@ -58,7 +60,7 @@ def get_model_fields(cls) -> list[FieldMeta]:
         fields_meta: list[FieldMeta] = []
 
         for field in type_info.fields:
-            annotation = cls.__model__.__annotations__[field.name]
+            annotation = get_type_hints(cls.__model__, include_extras=True)[field.name]
             if field.default is not msgspec.NODEFAULT:
                 default_value = field.default
             elif field.default_factory is not msgspec.NODEFAULT:

tests/test_msgspec_factory.py

@@ -2,7 +2,7 @@
 import sys
 from decimal import Decimal
 from enum import Enum
-from typing import Any, Dict, FrozenSet, List, NewType, Set, Tuple, Type, Union
+from typing import Any, Dict, FrozenSet, Generic, List, NewType, Set, Tuple, Type, TypeVar, Union
 from uuid import UUID
 
 import msgspec
@@ -227,3 +227,40 @@ class FooFactory(MsgspecFactory[Foo]):
 
     foo = FooFactory.build()
     assert len(foo.items) == 3
+
+
+def test_inheritence() -> None:
+    class Foo(Struct):
+        int_field: int
+
+    class Bar(Foo):
+        pass
+
+    class BarFactory(MsgspecFactory[Bar]):
+        __model__ = Bar
+
+    bar = BarFactory.build()
+    bar_dict = structs.asdict(bar)
+
+    validated_bar = msgspec.convert(bar_dict, type=Bar)
+    assert validated_bar == bar
+
+
+def test_inheritence_with_generics() -> None:
+    T = TypeVar("T")
+
+    class Foo(Struct, Generic[T]):
+        int_field: int
+        generic_field: T
+
+    class Bar(Foo[str]):
+        pass
+
+    class BarFactory(MsgspecFactory[Bar]):
+        __model__ = Bar
+
+    bar = BarFactory.build()
+    bar_dict = structs.asdict(bar)
+
+    validated_bar = msgspec.convert(bar_dict, type=Bar)
+    assert validated_bar == bar