Add support for stringified annotations when using PrivateAttr with…

… `Annotated` (pydantic#10157)

Co-authored-by: Alex Hall <[email protected]>

pydantic/_internal/_model_construction.py

@@ -4,13 +4,14 @@
 
 import builtins
 import operator
+import sys
 import typing
 import warnings
 import weakref
 from abc import ABCMeta
 from functools import lru_cache, partial
 from types import FunctionType
-from typing import Any, Callable, Generic, Literal, NoReturn
+from typing import Any, Callable, ForwardRef, Generic, Literal, NoReturn
 
 import typing_extensions
 from pydantic_core import PydanticUndefined, SchemaSerializer
@@ -28,7 +29,13 @@
 from ._mock_val_ser import set_model_mocks
 from ._schema_generation_shared import CallbackGetCoreSchemaHandler
 from ._signature import generate_pydantic_signature
-from ._typing_extra import get_cls_types_namespace, is_annotated, is_classvar, parent_frame_namespace
+from ._typing_extra import (
+    eval_type_backport,
+    get_cls_types_namespace,
+    is_annotated,
+    is_classvar,
+    parent_frame_namespace,
+)
 from ._utils import ClassAttribute, SafeGetItemProxy
 from ._validate_call import ValidateCallWrapper
 
@@ -430,6 +437,14 @@ def inspect_namespace(  # noqa C901
             and ann_type not in all_ignored_types
             and getattr(ann_type, '__module__', None) != 'functools'
         ):
+            if isinstance(ann_type, str):
+                # Walking up the frames to get the module namespace where the model is defined
+                # (as the model class wasn't created yet, we unfortunately can't use `cls.__module__`):
+                frame = sys._getframe(2)
+                if frame is not None:
+                    ann_type = eval_type_backport(
+                        ForwardRef(ann_type), globalns=frame.f_globals, localns=frame.f_locals
+                    )
             if is_annotated(ann_type):
                 _, *metadata = typing_extensions.get_args(ann_type)
                 private_attr = next((v for v in metadata if isinstance(v, ModelPrivateAttr)), None)

tests/test_annotated.py

@@ -424,18 +424,20 @@ def test_annotated_private_field_with_default():
     class AnnotatedPrivateFieldModel(BaseModel):
         _foo: Annotated[int, PrivateAttr(default=1)]
         _bar: Annotated[str, 'hello']
+        _baz: 'Annotated[str, PrivateAttr(default=2)]'
 
     model = AnnotatedPrivateFieldModel()
     assert model._foo == 1
+    assert model._baz == 2
 
-    assert model.__pydantic_private__ == {'_foo': 1}
+    assert model.__pydantic_private__ == {'_foo': 1, '_baz': 2}
 
     with pytest.raises(AttributeError):
         assert model._bar
 
     model._bar = 'world'
     assert model._bar == 'world'
-    assert model.__pydantic_private__ == {'_foo': 1, '_bar': 'world'}
+    assert model.__pydantic_private__ == {'_foo': 1, '_bar': 'world', '_baz': 2}
 
     with pytest.raises(AttributeError):
         assert model.bar