actix-ws: Session should implement Sink

[ricoriedel]

Hello everyone!

I am currently working on a project with websockets and ran into a small issue. I wanted to test the part of my application that sends the websocket messages using actix_ws::Session. Instead of starting a fake sever and using a real websocket client, I wanted to test the message exchange by replacing Session with a channel.

Although actix_ws::MessageStream implements Stream, actix_ws::Session does not implement Sink. Changing this would make testing much easier.

Thank you for your hard work maintaining this awesome project!

Edit: My apologies, the Sender inside Session does not implement Sink. This makes it more difficult to implement.

[ricoriedel]

The easiest way to implement this is using tokio_util::sync::PollSender, which does however come with a small performance penalty. Here is an implementation keeping the functionality the same.

https://github.com/ricoriedel/actix-extras/commit/1a3ad5e28ea17d05ba2427e8936a006c24708fa3

However, if we remove the close logic, the code becomes trivial wrapper and more consistent.

https://github.com/ricoriedel/actix-extras/commit/5e93efb4a5b16d3e021be4d76515d64c8061d6c9

I think it would actually be better to remove it and add an optional abstraction the user can create that ensures only one close message is sent and that also validates continuations. The session is essentially a channel anyway and most channels don't allow you to close them from the sender side.

Should I create a pull request?