fix: support unresolved forward refs in annotated dependencies

fastapi/dependencies/utils.py

@@ -242,10 +242,21 @@ def get_typed_signature(call: Callable[..., Any]) -> inspect.Signature:
     return typed_signature
 
 
+class _DictWithForwardRefs(dict[str, Any]):
+    def __missing__(self, key: str) -> Any:
+        value = ForwardRef(key)
+        self[key] = value
+        return value
+
+
 def get_typed_annotation(annotation: Any, globalns: dict[str, Any]) -> Any:
     if isinstance(annotation, str):
+        annotation_string = annotation
         annotation = ForwardRef(annotation)
         annotation = evaluate_forwardref(annotation, globalns, globalns)
+        if isinstance(annotation, ForwardRef) and "Annotated" in annotation_string:
+            annotationns = _DictWithForwardRefs(globalns)
+            annotation = eval(annotation_string, annotationns, annotationns)
         if annotation is type(None):
             return None
     return annotation

tests/test_stringified_annotation_dependency.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from dataclasses import dataclass
 from typing import TYPE_CHECKING, Annotated
 
 import pytest
@@ -27,6 +28,25 @@ async def get_client() -> AsyncGenerator[DummyClient, None]:
 
 Client = Annotated[DummyClient, Depends(get_client)]
 
+app_with_late_forward_ref = FastAPI()
+
+
+def get_potato() -> Potato:
+    return Potato(color="red", size=10)
+
+
+@app_with_late_forward_ref.get("/")
+async def get_late_forward_ref(
+    potato: Annotated[Potato, Depends(get_potato)],
+) -> dict[str, str]:
+    return {"color": potato.color}
+
+
+@dataclass
+class Potato:
+    color: str
+    size: int
+
 
 @pytest.fixture(name="client")
 def client_fixture() -> TestClient:
@@ -77,3 +97,43 @@ def test_openapi_schema(client: TestClient):
             },
         }
     )
+
+
+def test_late_forward_ref_dependency():
+    client = TestClient(app_with_late_forward_ref)
+
+    response = client.get("/")
+
+    assert response.status_code == 200, response.text
+    assert response.json() == {"color": "red"}
+
+
+def test_late_forward_ref_dependency_openapi():
+    assert app_with_late_forward_ref.openapi() == snapshot(
+        {
+            "openapi": "3.1.0",
+            "info": {"title": "FastAPI", "version": "0.1.0"},
+            "paths": {
+                "/": {
+                    "get": {
+                        "summary": "Get Late Forward Ref",
+                        "operationId": "get_late_forward_ref__get",
+                        "responses": {
+                            "200": {
+                                "description": "Successful Response",
+                                "content": {
+                                    "application/json": {
+                                        "schema": {
+                                            "additionalProperties": {"type": "string"},
+                                            "type": "object",
+                                            "title": "Response Get Late Forward Ref  Get",
+                                        }
+                                    }
+                                },
+                            }
+                        },
+                    }
+                }
+            },
+        }
+    )