ASGI Middleware helpers

[martino87r]

Hi there, I'm currently struggling to create a simple middleware for a Quart project; although I know that what I want already exists I want to try to create it myself first to learn about the ASGI interface on a practical level.

I'm using HTMX so I want to create a middleware that checks the current headers for the hx-request and evetually pass the flag down to the request object.

Ex: request.state.htmx

According to the source code, this seems actually impossible; I've also compared how starlette does things and they provide nice wrappers for the ASGI middleware, providing parsers for request and headers so you can manipulate them easily with the context of a generic ASGI middleware.

The second middleware I wanted to implement is a tracing one to figure out various timings (ex. SQL queries, template rendering times etc.), but without docs or helpers I can't wrap my head around it.
Any tips or suggestions would be greatly appreciated.

[aenglander]

For middleware, the only good resources I know is the documentation.

• https://asgi.readthedocs.io/en/latest/specs/main.html#middleware
• https://quart.palletsprojects.com/en/latest/how_to_guides/middleware/

You may also be able to just hook into the before_request lifecycle or signals rather than middleware. The Flask documentation can be used for exaplanations and examples with one change. All decorated functions need to be async.

[martino87r]

Actually I wasn't convinced by signals (I've used them in Flask) because the documentation doesn't mention them at all, and I thought they might interfere with the async request flow somehow. I'll give them a try later on.

Thanks for the info, once I figure it out somehow I'll try to drop a PR to improve the situation with the docs.