Allow closing `WSMessageHandler` stream with a close code

[liautaud]

Hi! First of all thanks for the library, it's been really great to use.

Would you be open to adding a way for a WSMessageHandler to close the server stream with .close(code: closeCode) frames in some way or another? The typical use case is closing a WebSocket connection after some unrecoverable error while wanting the client-side to know what the error actually is–in JavaScript, for instance, you can read event.code on a WebSocket "close" event.

I could already implement this behavior by falling back to the more cumbersome WSHandler level, but it seems like a frequent enough use case that it would make sense at the WSMessageHandler level too.

[swhitty]

Yeah I think it makes sense. Just looking at Mozilla docs, would it make sense for something like this?

public enum WSMessage: @unchecked Sendable, Hashable {
     case text(String)
     case data(Data)
     case close(code: WSCloseCode = .normalClosure, reason: String = "")
}

And then I think the AsyncStream<WSMessage> (from WSMessageHandler) would then always emit the .close message before the sequence ends?

This would also allow servers to send case .close to clients. We could validate that close is only ever sent to clients once..

What do you think?

[swhitty]

FYI the main branch has this new case allowing servers to send and receive custom close codes and reasons from clients.

I'm interested if this works for your use case.

Updated to the following:

public enum WSMessage: @unchecked Sendable, Hashable {
    case text(String)
    case data(Data)
    case close(WSCloseCode = .normalClosure)
}

[swhitty]

Available in the 0.22.0 release