Falcon: inject params from async context managers

async_deps.py

import logging

import aiohttp
import falcon
import falcon.asgi

# NOTE(vytas): Useful since ASGI otherwise has nothing like wsgierrors.
logging.basicConfig(
    format='%(asctime)s [%(levelname)s] %(message)s', level=logging.INFO)


class ContextMiddleware:
    def __init__(self, deps):
        self._deps = deps

    async def process_resource(self, req, resp, resource, params):
        async def close_stuff():
            for gen in gens:
                async for _ in gen:
                    pass

        gens = []
        for name, dep in self._deps.items():
            gens.append(gen := dep())
            params[name] = await gen.asend(None)

        resp.schedule(close_stuff)


class IPResource:
    async def on_get(self, req, resp, session):
        async with session.get('https://api.ipify.org') as ip_resp:
            ip = await ip_resp.text()
            resp.media = {'ip': ip}


async def aiohttp_session():
    async with aiohttp.ClientSession() as session:
        logging.info(f'instantiated {session}')
        yield session
        logging.info(f'tearing down {session}')


context_stack = ContextMiddleware({'session': aiohttp_session})
app = falcon.asgi.App(middleware=[context_stack])
app.add_route('/ip', IPResource())