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🐛 Fix TYPE_CHECKING annotations for Python 3.14 (PEP 649) #14789

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Merged
tiangolo merged 2 commits into from
Feb 4, 2026
Merged

🐛 Fix TYPE_CHECKING annotations for Python 3.14 (PEP 649) #14789

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5567c7d
Fix support for unevaluated stringified annotations (Python 3.14)
mgu Jan 31, 2026
3d7abf2
Remove xfail mark on test that now works with python 3.14
mgu Jan 31, 2026
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7 changes: 6 additions & 1 deletion fastapi/dependencies/utils.py
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Original file line number Diff line number Diff line change
Expand Up @@ -204,7 +204,12 @@ def _get_signature(call: Callable[..., Any]) -> inspect.Signature:
except NameError:
# Handle type annotations with if TYPE_CHECKING, not used by FastAPI
# e.g. dependency return types
signature = inspect.signature(call)
if sys.version_info >= (3, 14):
from annotationlib import Format

signature = inspect.signature(call, annotation_format=Format.FORWARDREF)
else:
signature = inspect.signature(call)
else:
signature = inspect.signature(call)
return signature
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30 changes: 30 additions & 0 deletions tests/test_stringified_annotation_dependency_py314.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,30 @@
from typing import TYPE_CHECKING, Annotated

from fastapi import Depends, FastAPI
from fastapi.testclient import TestClient

from .utils import needs_py314

if TYPE_CHECKING: # pragma: no cover

class DummyUser: ...


@needs_py314
def test_stringified_annotation():
# python3.14: Use forward reference without "from __future__ import annotations"
async def get_current_user() -> DummyUser | None:
return None

app = FastAPI()

client = TestClient(app)

@app.get("/")
async def get(
current_user: Annotated[DummyUser | None, Depends(get_current_user)],
) -> str:
return "hello world"

response = client.get("/")
assert response.status_code == 200
10 changes: 8 additions & 2 deletions tests/test_tutorial/test_dependencies/test_tutorial008.py
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
import importlib
import sys
from types import ModuleType
from typing import Annotated, Any
from unittest.mock import Mock, patch
Expand All @@ -12,8 +13,13 @@
name="module",
params=[
"tutorial008_py39",
# Fails with `NameError: name 'DepA' is not defined`
pytest.param("tutorial008_an_py39", marks=pytest.mark.xfail),
pytest.param(
"tutorial008_an_py39",
marks=pytest.mark.xfail(
sys.version_info < (3, 14),
reason="Fails with `NameError: name 'DepA' is not defined`",
),
),
],
)
def get_module(request: pytest.FixtureRequest):
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4 changes: 2 additions & 2 deletions tests/utils.py
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Expand Up @@ -6,8 +6,8 @@
needs_py310 = pytest.mark.skipif(
sys.version_info < (3, 10), reason="requires python3.10+"
)
needs_py_lt_314 = pytest.mark.skipif(
sys.version_info >= (3, 14), reason="requires python3.13-"
needs_py314 = pytest.mark.skipif(
sys.version_info < (3, 14), reason="requires python3.14+"
)


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