Make WebsocketImplProtocol async iterable

[ChihweiLHBird]

Make websocket object iterable. Will add tests later when the code has been finalized.

Update:
Manual test was okay. Currently we don't have a test client in Sanic that can send and receive WebSocket messages, so it seems impossible to have a test case for this feature at this time.

[codecov]

Codecov Report

Base: 87.844% // Head: 88.425% // Increases project coverage by +0.581% 🎉

Coverage data is based on head (66a9389) compared to base (389363a).
Patch coverage: 83.333% of modified lines in pull request are covered.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #2490       +/-   ##
=============================================
+ Coverage   87.844%   88.425%   +0.581%     
=============================================
  Files           78        78               
  Lines         6466      6471        +5     
  Branches      1247      1247               
=============================================
+ Hits          5680      5722       +42     
+ Misses         560       517       -43     
- Partials       226       232        +6     

Impacted Files	Coverage Δ
sanic/server/websockets/impl.py	37.115% <83.333%> (+7.929%)	⬆️
sanic/app.py	88.204% <0.000%> (+0.704%)	⬆️
sanic/server/websockets/frame.py	92.523% <0.000%> (+0.934%)	⬆️
sanic/server/protocols/websocket_protocol.py	73.015% <0.000%> (+3.174%)	⬆️

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[Tronic]

Still preferring a solution that only uses __aiter__. Don't care which way it is done.

[ChihweiLHBird]

Still preferring a solution that only uses __aiter__. Don't care which way it is done.

Just removed __anext__, lol.

[Tronic]

Thanks for the PR. This is a very useful feature and it helps to have parity with the websockets module. Receive on a closed socket should probably follow that as well, and no-error on clean close seems like the right thing to do anyway. Will approve as is if no-one else comments on that, with the code changes suggested.

[ahopkins]

Can you add a test?

[ChihweiLHBird]

Can you add a test?

Our test client with WebSocket mimic client support was not released so the CI would fail in this PR. Can we do a release or point the version of sanic-testing to the repo?

[ahopkins]

Ooo nice! Yeah, I'll do that.