Make WebSocket adapter more changeable

[nakasyou]

What is the feature you are proposing?

I propose createUpgradeWebSocket helper and WSContext class.

For example, you can implement Deno adapter like this:

export const upgradeWebSocket: UpgradeWebSocket = createUpgradeWebSocket((c, events, options) => {
  const { response, socket } = Deno.upgradeWebSocket(c.req.raw, options ?? {})

  const wsContext = new WSContext({
    close: (code, reason) => socket.close(code, reason),
    get protocol() {
      return socket.protocol
    },
    raw: socket,
    get readyState() {
      return socket.readyState as WSReadyState
    },
    url: socket.url,
    send: (source) => socket.send(source)
  })
  socket.onopen = (evt) => events.onOpen?.(evt, wsContext)
  socket.onmessage = (evt) => events.onMessage?.(evt, wsContext)
  socket.onclose = (evt) => events.onClose?.(evt, wsContext)
  socket.onerror = (evt) => events.onError?.(evt, wsContext)

  return response
})

Current issues

Currently, adapter creators have to change code if WSContext or UpgradeWebSocket API interface is changed. Hono provides an interface to implement custom WebSocket adapter. So changing WSContext or UpgradeWebSocket API interface might be a breaking change. For example, #3466 changes an API.

And, WsContext repeats the same implementation between adapters. For example, binaryType: 'arraybuffer' is had by Bun, Deno. The change resolves it.

In order to make WebSocket adapter more changeable, I propose these APIs.