Questions about middlewares

I’d like to do a very simple task, that is add a middleware which runs before the endpoints and adds a few properties to the request object. Very similar to how authentication middleware does it, but I’d like to make it more flexible.

My aim is to have something like this:

• request.user_.user_data
• request.user_.org_data
• request.user_.allowed_regions for example

Now, my problem is the following:

• BaseHTTPMiddleware in the docs starts with response = await call_next(request) and it adds a Header after the request has been processed. How can I use BaseHTTPMiddleware to add processing before an endpoint runs?
• Can I add custom properties to the request object in a Middleware?
• In case I cannot do it with BaseHTTPMiddleware I’m confused about the pure ASGI 2 vs. 3. middlewares. All the examples in starlette 0.11.4 are on ASGI 2, but ProxyHeadersMiddleware from uvicorn github is ASGI 3, do I understand it right?
• I get a INFO: ASGI 'lifespan' protocol appears unsupported. if I try to add something based on the skeleton of ProxyHeadersMiddleware. Will it disappear if I upgrade to 0.12.beta?

[hyperknot]

OK, I’ve been able to make some progress trying to write my ASGI middleware for 0.12.

class JSONAuthMiddleware:
    def __init__(self, app):
        self.app = app

    async def __call__(self, scope, receive, send):
        if scope['type'] != 'http':
            response = PlainTextResponse('non http', status_code=400)
            await response(scope, receive, send)

        if scope['method'] != 'POST':
            response = PlainTextResponse('non POST', status_code=400)
            await response(scope, receive, send)

        request = Request(scope, receive=receive)
        data = await request.json()

        await self.app(scope, receive, send)

My problem is that if I add a request.json() line in the middleware, then it cannot be called in the view. When the view calls it, it stalls the app and uvicorn need to be force quitted (Waiting for connections to close. (CTRL+C to force quit)).

How can I solve this (or maybe this is a bug?).

[tomchristie]

There’s a bunch of different things being asked here, so I’m going to close this off as a general discussion rather than a narrowed-down actionable requested change.