Uvicorn silently ignores exceptions that occur during startup against the ASGI lifespan protocol - see starlette/issues/486.
\nYou can disable this feature using the lifespan=\"on\" parameter to uvicorn.run() - which Datasette now does as-of 16f592247a2a0e140ada487e9972645406dcae69
This exposed a bug in datasette-debug-asgi: it wasn't handling lifespan events correctly. datasette-debug-asgi/issues/1
The unit tests weren't catching this because using HTTPX to make test requests doesn't trigger lifespan events.
\nFlorimond Manca had run into this problem too, and built asgi-lifespan to address it.
\nYou can wrap an ASGI app in async with LifespanManager(app): and the correct lifespan events will be fired by that with block.
Here's how to use it to trigger lifespan events in a test:
\nfrom asgi_lifespan import LifespanManager\n\n@pytest.mark.asyncio\nasync def test_datasette_debug_asgi():\n ds = Datasette([], memory=True)\n app = ds.app()\n async with LifespanManager(app):\n async with httpx.AsyncClient(app=app) as client:\n response = await client.get(\"http://localhost/-/asgi-scope\")\n assert 200 == response.status_code\n assert \"text/plain; charset=UTF-8\" == response.headers[\"content-type\"]