Usage with aiohttp

aiohttp has no dependency-injection system of its own, so modern-di-aiohttp uses the @inject decorator with FromDI markers. setup_di opens the root container on app startup, closes it on cleanup, and installs middleware that opens a per-connection child container automatically.

How to use

1. Install modern-di-aiohttp

uvpip

uv add modern-di-aiohttp

pip install modern-di-aiohttp

2. Apply to your application

import dataclasses
import typing

from aiohttp import web
from modern_di import Container, Group, Scope, providers
from modern_di_aiohttp import FromDI, inject, setup_di


@dataclasses.dataclass(kw_only=True)
class Settings:
    debug: bool = True


class AppGroup(Group):
    settings = providers.Factory(scope=Scope.APP, creator=Settings)


@inject
async def homepage(
    request: web.Request,
    settings: typing.Annotated[Settings, FromDI(AppGroup.settings)],
) -> web.Response:
    return web.json_response({"debug": settings.debug})


app = web.Application()
app.router.add_get("/", homepage)
setup_di(app, Container(groups=[AppGroup], validate=True))

3. Scopes

An HTTP request opens a Scope.REQUEST child container; a WebSocket connection opens a Scope.SESSION one. Providers resolve from the connection's child container, so Scope.REQUEST providers live for exactly one request.

Which scope gets opened is decided per-connection: the middleware checks the request's handshake headers (via aiohttp's can_prepare), not the route or handler. A request carrying WebSocket-upgrade headers opens a Scope.SESSION child regardless of which handler ultimately serves it.

4. WebSockets and per-message scope

A WebSocket handler runs for the whole life of the socket, so its Scope.SESSION container does too. Read the connection with FromDI(aiohttp_websocket_provider). For per-message work, open a nested Scope.REQUEST child of the session container, fetched via fetch_request_container:

import typing

from aiohttp import web
from modern_di import Scope
from modern_di_aiohttp import FromDI, aiohttp_websocket_provider, fetch_request_container, inject


@inject
async def ws_handler(
    request: web.Request,
    connection: typing.Annotated[web.Request, FromDI(aiohttp_websocket_provider)],
) -> web.WebSocketResponse:
    session_container = fetch_request_container(request)
    ws = web.WebSocketResponse()
    await ws.prepare(request)
    async for msg in ws:
        if msg.type == web.WSMsgType.TEXT:
            async with session_container.build_child_container(scope=Scope.REQUEST) as request_container:
                ...  # resolve REQUEST-scoped providers for this message
    return ws