Missing close status codes for websockets

[achimnol]

🐞 Describe the bug

ref: https://developer.mozilla.org/en-US/docs/Web/API/CloseEvent
current: https://github.com/aio-libs/aiohttp/blob/707736b/aiohttp/http_websocket.py#L31-L42

The close code 1014, 1015 is missing, and one of my use case (websocket proxy) involves 1014,
which results in an unexpected error "Invalid close code: 1014".

I think we need to update the list.

[derlih]

@achimnol do you mean that the values are missing in the WSCloseCode enum?

[asvetlov]

There is an interesting question: how to prevent such problem in future, when a new code will be added again?

[derlih]

It could be a GitHub action that periodically fetchs the https://github.com/mdn/content/blob/main/files/en-us/web/api/closeevent/index.html , parses it and compares to the enum in master branch. In case of mismatch creates an issue with a tag.

[derlih]

@achimnol I think 1015 shouldn't be set in aiohttp. The connection error should be raised in this case IMHO.
From MDN:

Indicates that the connection was closed due to a failure to perform a TLS handshake (e.g., the server certificate can't be verified).

[achimnol]

Even the original RFC and its follow-up docs does not specify all of the close codes listed in the MDN document.
Since the status codes are largely left as "extensible", I think we should allow arbitrary unknown close codes in the range of 1000 to 4999 as valid with an optional conversion to pre-defined constant enums.

I agree with that 1015 might not be necessary for the application layer, i.e., aiohttp., but if we decide to accept any status code in the range of 1000 to 4999, this wouldn't be important anyway.

[derlih]

I think we are talking not only the enum values, but also about the handing the "unexpected" close codes.

aiohttp/aiohttp/http_websocket.py

Lines 282 to 293 in 2a9d5e9

	def _feed_data(self, data: bytes) -> Tuple[bool, bytes]:
	for fin, opcode, payload, compressed in self.parse_frame(data):
	if compressed and not self._decompressobj:
	self._decompressobj = zlib.decompressobj(wbits=-zlib.MAX_WBITS)
	if opcode == WSMsgType.CLOSE:
	if len(payload) >= 2:
	close_code = UNPACK_CLOSE_CODE(payload[:2])[0]
	if close_code < 3000 and close_code not in ALLOWED_CLOSE_CODES:
	raise WebSocketError(
	WSCloseCode.PROTOCOL_ERROR,
	f"Invalid close code: {close_code}",
	)

IMO the question is: should we change this behavior and how?
For example we could just use the value from close_code = UNPACK_CLOSE_CODE(payload[:2])[0] without additional checks and keep the enum to improve clearness of the code like http.HTTPStatus does.
But on the other hand it changes the behavior of the code.

May be it would be better to raise an excpetion if the code is not OK (1000).