Add nested forward-ref regression coverage

fastapi/dependencies/utils.py

@@ -1,3 +1,4 @@
+import builtins
 import dataclasses
 import inspect
 import sys
@@ -84,6 +85,8 @@ multipart_not_installed_error = (
 
 class _ForwardRefNamespace(dict[str, Any]):
     def __missing__(self, key: str) -> Any:
+        if hasattr(builtins, key):
+            return getattr(builtins, key)
         value = ForwardRef(key)
         self[key] = value
         return value
@@ -253,6 +256,9 @@ def get_typed_signature(call: Callable[..., Any]) -> inspect.Signature:
 def get_typed_annotation(annotation: Any, globalns: dict[str, Any]) -> Any:
     if isinstance(annotation, str):
         try:
+            # These annotation strings come from Python's own annotation machinery,
+            # not directly from user input, so evaluating them here matches the
+            # standard runtime resolution path.
             annotation = eval(annotation, globalns, globalns)
         except NameError:
             # Preserve the outer typing structure (e.g. Annotated[..., Depends(...)])

tests/test_stringified_annotations_forwardrefs.py

@@ -77,3 +77,44 @@ async def read_root(potato: Annotated["Potato", Depends(get_potato)]):
 
     operation = client.get("/openapi.json").json()["paths"]["/"]["get"]
     assert "parameters" not in operation
+
+
+@needs_py310
+def test_nested_forwardref_inside_annotated_dependency_preserves_structure():
+    app = _build_app("""
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Annotated
+
+from fastapi import Depends, FastAPI
+
+app = FastAPI()
+
+def get_potatoes() -> list[Potato]:
+    return [Potato(color="red", size=10), Potato(color="gold", size=7)]
+
+@app.get("/")
+async def read_root(potatoes: Annotated[list[Potato], Depends(get_potatoes)]):
+    return {
+        "items": [{"color": potato.color, "size": potato.size} for potato in potatoes]
+    }
+
+@dataclass
+class Potato:
+    color: str
+    size: int
+""")
+    client = TestClient(app)
+
+    response = client.get("/")
+    assert response.status_code == 200, response.text
+    assert response.json() == {
+        "items": [
+            {"color": "red", "size": 10},
+            {"color": "gold", "size": 7},
+        ]
+    }
+
+    operation = client.get("/openapi.json").json()["paths"]["/"]["get"]
+    assert "parameters" not in operation