jrycw / piccolo-api-middlewares

ASGI middlewares

piccolo-api-middlewares

This repository is a personal exercise focused on transitioning the middlewares within the Piccolo API from the async def dispatch(self, request, call_next) style to async def __call__(self, scope, receive, send).

Procedures

Here are some general procedures for transforming the middleware:

1. The middleware no longer needs to inherit from starlette.middleware.base.BaseHTTPMiddleware. Instead, replace super().__init__(app) with self.app = app.

2. Remove the dispatch method.

3. Add the __call__ method, a Python dunder method, with the signature async def __call__(self, scope, receive, send).

4. Retrieve required information from the scope (a dictionary). Starlette provides helpful functions or data structures for this purpose. For example, the request object can be obtained from request = starlette.requests.Request(scope).

5. Instead of directly returning the response, obtain a response, call it with scope, receive, send, await it, and then forcefully return.

6. receive and send are callable. Core business logic may need to be moved into these callables.

7. Finally, remember to call self.app with scope, receive, send, await it, and then forcefully return.

8. If you're open to adding the dependency, asgiref provides some useful type annotations.

References

• piccolo-api
• starlette
• starlette-csrf
• encode
• How to secure APIs built with FastAPI: A complete guide