Use of asgiref typing

Checklist

• There are no similar issues or pull requests for this yet.
• @JayH5 and @Kludex are positive about this idea, but it was not discussed on our Gitter channel.

Is your feature related to a problem? Please describe.

On uvicorn we started a mypy compliance goal since some time ago, and we’re about to accomplish it. On this road, we decided to use asgiref typing to annotate ASGI related types.

What I propose is that we do the same for Starlette.

Describe the solution you would like.

Remove the types.py module, and annotate everything that is needed with asgiref.typing types.

There’s no matching type to Message, as discussed on #1206 . So even if it would be more pleasant to our users, unfortunately it will be more troublesome to follow that path.

Describe alternatives you considered

Use Message as Union[ASGISendCallable, ASGIReceiveCallable] and solve the mypy issues. It will be more pleasant to ours users.

[br3ndonland]

The problem is that I’m not 100% sure, but I think what makes the issue hard to solve is the Message type. You’ll see the mypy errors if you experiment some changes locally.

That being said… I believe the approach would be:

1. Split Message into ASGISendEvent and ASGIReceiveEvent - naming matching asgiref.
2. Rename the other types to asgiref (just renaming, not introduce the package yet).
3. Remove the types definition and import from asgiref - this should be straightforward based on step 2.

I helped with type-annotating Uvicorn, and I’m happy to help here as well.

I’ve already made some good progress, and I’m on step 3 now. I need to correct a few type errors, now that we’re importing from the more specific asgiref types.

Should have a PR up shortly.

[Kludex]

@br3ndonland Cool! I’ll be happy to review it.

Just take in consideration that the steps mentioned were also a way to minimize the diff and make the review process easier. 🙏