from fastapi import Depends, FastAPI, Request

app = FastAPI()


class Session:
    def __init__(self):
        print("creating session")

    async def __aenter__(self):
        print("opening session")
        return self

    async def __aexit__(self, exc_type, exc, tb):
        print("closing session")

    async def commit(self):
        print("committing session")

    async def rollback(self):
        print("rolling back session")


@app.middleware("http")
async def commit_session(request: Request, call_next):
    # minimalistic middleware for example, my code uses ASGI middleware
    response = await call_next(request)
    db_session = request.scope.get("db_session")
    if not db_session:
        return response

    if response.status_code // 200 != 1:
        await db_session.rollback()
    else:
        await db_session.commit()

    return response


async def get_db_session(request: Request):
    async with Session() as session:
        request.scope["db_session"] = session
        yield session


@app.get("/")
async def root(session: Session = Depends(get_db_session)):
    return {"message": "Hello World"}


# Pre 0.106 behaviour:

# creating session
# opening session
# committing session
# closing session

# Post 0.106 behaviour:
# creating session
# opening session
# closing session
# committing session

# The session is not committed, because it's closed before the middleware is called.