test_app_lifespans.py

from contextlib import asynccontextmanager
from typing import AsyncGenerator

from fastapi import FastAPI, APIRouter, Request
from fastapi.testclient import TestClient


def test_lifecycle_subrouters():
    @asynccontextmanager
    async def app_lifespan(app: FastAPI) -> AsyncGenerator[dict[str, bool], None]:
        yield {"app": True}

    @asynccontextmanager
    async def router_lifespan(app: FastAPI) -> AsyncGenerator[dict[str, bool], None]:
        yield {"router": True}

    @asynccontextmanager
    async def subrouter_lifespan(app: FastAPI) -> AsyncGenerator[dict[str, bool], None]:
        yield {"subrouter": True}

    subrouter = APIRouter(lifespan=subrouter_lifespan)

    router = APIRouter(lifespan=router_lifespan)
    router.include_router(subrouter)
    app = FastAPI(lifespan=app_lifespan)
    app.include_router(router)

    @app.get("/state")
    def get_state(request: Request):
        return request.state._state

    with TestClient(app) as client:
        assert client.get("/state").json() == {
            "app": True,
            "router": True,
            "subrouter": True,
        }


def test_lifecycle_subapps():
    @asynccontextmanager
    async def app_lifespan(app: FastAPI) -> AsyncGenerator[dict[str, bool], None]:
        yield {"app": True}

    @asynccontextmanager
    async def subapp_lifespan(app: FastAPI) -> AsyncGenerator[dict[str, bool], None]:
        yield {"subapp": True}

    subapp = FastAPI(lifespan=subapp_lifespan)

    @subapp.get("/state")
    def get_subapp_state(request: Request):
        return request.state._state

    app = FastAPI(lifespan=app_lifespan)
    app.mount("/subapp", subapp)

    @app.get("/state")
    def get_state(request: Request):
        return request.state._state

    with TestClient(app) as client:
        assert client.get("/state").json() == {
            "app": True,
        }
        # This fails: we get {"app": True} instead.
        assert client.get("/subapp/state").json() == {
            "app": True,
            "subapp": True,
        }