Bug - Unittest indefinitely hangs when using BaseHTTPMiddleware, sync router and quit(). Needs MainThread _daemonic hack.

[arrman-saha]

When a BaseHTTPMiddleware is used, and we want to quit the application in the router everything works as expected when deploying the app. However unit testcases permanently hang if we use a sync router. To make the testcases not hang we need a hack - setattr(threading.main_thread(), "_daemonic", True). But this hack is not needed for async router.

I've tried looking for similar issues but can't find something similar.

I originally thought this was a fastapi issue, but seems like this is a starlette issue.

The following code will hang indefinitely after testcases have passed, unless either the async def part is used or setattr part is used.

import unittest
from starlette.applications import Starlette
from starlette.middleware.base import BaseHTTPMiddleware
from starlette.middleware import Middleware
from starlette.testclient import TestClient
from starlette.routing import Route

# async def just_quit(_):  # Async def does not need the MainThread _daemonic hack
def just_quit(_):
    quit(1)

class NothingMiddleware(BaseHTTPMiddleware):
    def __init__(self,app,):
        super().__init__(app)
    async def dispatch(self, request, call_next):
        return await call_next(request)

app = Starlette(debug=False, routes=[Route("/quit", just_quit)], middleware=[Middleware(NothingMiddleware)])

class TestQuitEndpoint(unittest.TestCase):

    def test_SystemExit(self):
        # Non async def needs this MainThread _daemonic hack.
        # import threading
        # setattr(threading.main_thread(), "_daemonic", True)
        # Testcase
        with self.assertRaises(RuntimeError):
            with TestClient(app) as client:
                with self.assertRaises(SystemExit):
                    client.get("/quit")

if __name__ == '__main__':
    unittest.main()

[arrmansa]

Hi, looks like anyio worker threads were getting stuck because BaseException was not handled in BaseHTTPMiddleware. Can I open a PR for this ?
master...arrmansa:starlette:master

(The ask account is different because I accidentally started discussion from my work account. I'm not trying to spam the discussions with an alt or anything.)