[Python] TypeError in FastAPI when using APIRoute with a Router

I have a FastAPI backend and i'm trying to implement an APIRoute class to handle logic before and after the request (logging).

# app.py
from fastapi import FastAPI, APIRouter

from backend.app.routers import questions


API_VERSION = "v1"

app = FastAPI(lifespan=lifespan)
api_v1_router = APIRouter(prefix=f"/{API_VERSION}")
api_v1_router.include_router(questions.router)
app.include_router(api_v1_router)

if __name__ == "__main__":
import uvicorn

uvicorn.run(app, host="0.0.0.0", port=80)


# questions.py
from typing import Callable
from fastapi import APIRouter, Request, Response

class LoggingAPIRoute(APIRoute):
@staticmethod
async def access_log_req(request: Request) -> None:
print("request...")

@staticmethod
async def access_log_res(request: Request, response: Response) -> None:
print("response...")

async def get_route_handler(self) -> Callable:
original_route_handler = super().get_route_handler()

async def custom_route_handler(request: Request) -> Response:
await self.access_log_req(request=request)
try:
response = await original_route_handler(request)
await self.access_log_res(request=request, response=response)
return response
except Exception as e:
return "oh snap!"

return custom_route_handler


router = APIRouter(route_class=LoggingAPIRoute)

@router.post("/retrieve", response_class=JSONResponse)
async def retrieve(request: Request, auth_result: str = Security(auth.verify)):
pass



Calling the v1/retrieve with curl causes an exception to be thrown: TypeError: the first argument must be callable. When removing LoggingAPIRoute usage from the router, the problem is solved.

Any ideas?

curl localhost:80/v1/retrieve -X POST

INFO: 127.0.0.1:52860 - "POST /v1/retrieve HTTP/1.1" 500 Internal Server Error
ERROR: Exception in ASGI application
Traceback (most recent call last):
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/uvicorn/protocols/http/h11_impl.py", line 403, in run_asgi
result = await app( # type: ignore[func-returns-value]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
self.scope, self.receive, self.send
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
)
^
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/uvicorn/middleware/proxy_headers.py", line 60, in __call__
return await self.app(scope, receive, send)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/fastapi/applications.py", line 1054, in __call__
await super().__call__(scope, receive, send)
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/starlette/applications.py", line 112, in __call__
await self.middleware_stack(scope, receive, send)
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/starlette/middleware/errors.py", line 187, in __call__
raise exc
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/starlette/middleware/errors.py", line 165, in __call__
await self.app(scope, receive, _send)
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/starlette/middleware/cors.py", line 85, in __call__
await self.app(scope, receive, send)
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/starlette/middleware/exceptions.py", line 62, in __call__
await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
raise exc
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
await app(scope, receive, sender)
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/starlette/routing.py", line 714, in __call__
await self.middleware_stack(scope, receive, send)
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/starlette/routing.py", line 734, in app
await route.handle(scope, receive, send)
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/starlette/routing.py", line 288, in handle
await self.app(scope, receive, send)
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/starlette/routing.py", line 76, in app
await wrap_app_handling_exceptions(app, request)(scope, receive, send)
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
raise exc
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
await app(scope, receive, sender)
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/starlette/routing.py", line 73, in app
response = await f(request)
^^^^^^^^^^^^^^^^
File "/Users/boss/foo/.venv/lib/python3.13/site-packages/starlette/concurrency.py", line 36, in run_in_threadpool
func = functools.partial(func, *args, **kwargs)
TypeError: the first argument must be callable

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