When use --interface=wsgi and --lifespan=on there was something wrong

[ryomahan]

When we start a WSGI Application use uvicorn with options: --interface=wsgi --lifespan=on there will throw an error like:

Traceback (most recent call last):
  File ".../python3.9/site-packages/uvicorn/lifespan/on.py", line 86, in main
    await app(scope, self.receive, self.send)
  File ".../python3.9/site-packages/uvicorn/middleware/proxy_headers.py", line 78, in __call__
    return await self.app(scope, receive, send)
  File ".../python3.9/site-packages/uvicorn/middleware/wsgi.py", line 87, in __call__
    assert scope["type"] == "http"
AssertionError

but when we only use --interface=wsgi the WSGI Application will run successfully, and the interesting thing is lifespan option default value is "auto" and the auto lifespan is equal with on lifespan, they all use uvicorn.lifespan.on:LifespanOn.

There is two ways to resolve:

1. raise error when use --interface=wsgi with uvicorn.lifespan.on:LifespanOn, whether --lifespan=on or --lifespan=auto
2. just log error when use --interface=wsgi with --lifespan=on or --lifespan=auto

I choose the second way to resolve it and push a PR.

[ryomahan]

the PR #1632

[Kludex]

How can I reproduce it?

[Kludex]

Do you run uvicorn app:app --interface=wsgi, and works properly?

[ryomahan]

yeah, of course.

[ryomahan]

because in the uvicorn.lifespan.on.py:LifespanOn.main have code like this:

...
            if self.config.lifespan == "auto":
                msg = "ASGI 'lifespan' protocol appears unsupported."
                self.logger.info(msg)
...

and the lifespan default value is auto, so when we use uvicorn app:app --interface=wsgi this code will help us pass error raise.

[Kludex]

I don't see a strong case to do something about this. We don't do validation on CLI parameters, yet at least.

[ryomahan]

as we know, lifespan is a ASGI concept, so --interface=wsgi should not use with --lifespan=on or --lifespan=auto.

two way to resolve:

1. when we use both together, raise an error
2. when we use both together, loggin an error msg but don't termination

and now, we get yes when we use --interface=wsgi --lifespan=auto and get no when we use --interface=wsgi --lifespan=on, but as I say they(--lifespan=auto and --lifespan=on) all use uvicorn.lifespan.on:LifespanOn, that means I use the same thing but get different result.

yeah, maybe there isn't a strong case to do something, I just find it and push it.