CORS support about starlette HOT 4 CLOSED

Thinking about this a bit more, what may be most important, at least for my understanding, is determining a potential view pattern. From what I can gather looking at the CORS extensions for other projects (including both WSGI and asyncio) is that they generally assume some application-level configuration but also that a wrapped application will return a mutable response.

I can potentially see how to implement generic CORS behavior for Starlette in a similar way if I base it around something like the pattern proposed in #35, but I haven't thought of an alternative as of yet.

from starlette.

Following up on the last comment, I've realized that theasgi_application method may be all that is necessary for implementing this behavior. I'm going to close this in favor of using the views issue for any further discussion on this #27 since it seems mostly related to that rather than CORS support specifically.

from starlette.

but enabling CORS support would require altering the response class headers which cannot be accomplished simply by wrapping the ASGI app at this point.

Right - response middleware is more awkward that request middleware, because you need to wrap the send callable that gets passed to the application. If you do that then you can intercept the outgoing response, and modify the headers.

I'd far prefer that we implement CORS in middleware, than as part of a view pattern.

from starlette.

Here's one kinda pattern that I think would work...

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

    def __call__(self, scope):
        return functools.partial(self.handler, scope=scope)

    async def handler(self, receive, send, scope=None):
        sender = functools.partial(self.sender, send=send)
        inner = self.app(scope)
        await inner(receive, sender)

    async def sender(message, send=None):
        if message['type'] == 'http.response':
            headers = Headers(message['headers'])
            headers['...'] = '...'
        await send(message)

from starlette.