aiohttp middleware and replacing a request in flight

[jerblack]

Hi, I am trying to build a middleware that attempts to automatically add slashes to the end of uris that are missing them to avoid having to double-define all my routes with and without a trailing slash to ensure no one 404s. I saw your normalize_path_middleware and started with that, but I can't use anything that's going to force a redirect on the client. I need to be able to accomplish the same thing entirely on the server side.

Here's my attempt at that middleware, which just clones the request with a new rel_url and passes that along, but I still am getting 404s when I don't include a trailing backslash in my uris. Any ideas? Thanks.

from aiohttp.web_urldispatcher import SystemRoute

def middleware(f):
    f.__middleware_version__ = 1
    return f

def trailing_slashes():
    @middleware
    async def impl(request, handler):
        if isinstance(request.match_info.route, SystemRoute):
            rel_url = str(request.rel_url)
            if '?' in rel_url:
                path, query = rel_url.split('?', 1)
                query = f'?{query}'
            else:
                path = rel_url
                query = ''
            if not path.endswith('/'):
                rel_url = f'{path}/{query}'
                request = request.clone(rel_url=rel_url)

        return await handler(request)

    return impl

And here is a sample class that implements it.

from aiohttp import web
import slashes_mw

class ClassName(object):
    def __init__(self):
        self.app = web.Application(middlewares=[slashes_mw.trailing_slashes()])
        self.app.add_routes(self.get_routes())
        web.run_app(self.app, port=80, host='0.0.0.0')

    def get_routes(self):
        return [
            web.get('/', self.handler),
            web.get('/{name}/', self.handler)
        ]

    def handler(self, request):
        return web.Response(text='hello')

ClassName()

[asvetlov]

There is something wrong if you cannot use redirects on your site.

[jerblack]

It's not a site, it's an API that will be exposed to IoT devices that won't be able to redirect to another url.

[asvetlov]

I see nothing bad with registering a handler twice than.
It works faster than middleware processing BTW.

[jerblack]

Can I get a yes or no answer on whether or not the technical question I am asking is possible?

[asvetlov]

Well, if you insist.
You need to call app.router.resolve() to find a new match_info and call a new handler.
Not sure if there are no pitfalls (another middlewares for a new route, API forward compatibility etc) -- it touches a private API.
Anyway reading https://github.com/aio-libs/aiohttp/blob/master/aiohttp/web_app.py#L313-L352 can help you to master something.

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a [new issue] for related bugs.
If you feel like there's important points made in this discussion, please include those exceprts into that [new issue].
[new issue]: https://github.com/aio-libs/aiohttp/issues/new