Ensure auto request connectons are released

The after request functions are not called if the connection is
aborted (thereby resulting in a CancelledError), thereby resulting in
a leaked connection. The teardown request function is always called,
hence the switch.

It is easier, and sufficient, to test for aiosqlite only.

src/quart_db/extension.py

@@ -6,7 +6,7 @@
 from urllib.parse import urlsplit
 
 import click
-from quart import g, Quart, Response
+from quart import g, Quart
 from quart.cli import pass_script_info, ScriptInfo
 
 from ._migration import setup_schema
@@ -116,7 +116,7 @@ def init_app(self, app: Quart) -> None:
 
         if app.config.get("QUART_DB_AUTO_REQUEST_CONNECTION", self._auto_request_connection):
             app.before_request(self.before_request)
-            app.after_request(self.after_request)
+            app.teardown_request(self.teardown_request)
 
         app.cli.add_command(_migrate_command)
         app.cli.add_command(_schema_command)
@@ -137,11 +137,10 @@ async def after_serving(self) -> None:
     async def before_request(self) -> None:
         g.connection = await self.acquire()
 
-    async def after_request(self, response: Response) -> Response:
+    async def teardown_request(self, _exception: Optional[BaseException]) -> None:
         if getattr(g, "connection", None) is not None:
             await self.release(g.connection)
         g.connection = None
-        return response
 
     async def migrate(self) -> None:
         migrations_folder = None

tests/test_basic.py

@@ -1,3 +1,7 @@
+from asyncio import CancelledError
+from typing import NoReturn, Type
+
+import pytest
 from quart import g, Quart, ResponseReturnValue
 
 from quart_db import QuartDB
@@ -16,3 +20,24 @@ async def index() -> ResponseReturnValue:
         response = await test_client.get("/")
         data = await response.get_data(as_text=True)
     assert data == "test"
+
+
+@pytest.mark.parametrize(
+    "exception",
+    [CancelledError, ValueError],
+)
+async def test_g_connection_release(url: str, exception: Type[Exception]) -> None:
+    if not url.startswith("sqlite"):
+        pytest.skip("aiosqlite - simpler backend to test")
+
+    app = Quart(__name__)
+    db = QuartDB(app, auto_request_connection=True, url=url)
+
+    @app.get("/")
+    async def index() -> NoReturn:
+        raise exception()
+
+    async with app.test_app():
+        test_client = app.test_client()
+        await test_client.get("/")
+    assert db._backend._connections == set()  # type: ignore