How to pass data on request upgrade?

[jarda-svoboda]

In regular bun server, you can attach user data to the ws handler using data object like this:server.upgrade(req, { data: { username } }) (docs) – is it somehow possible within your adapter?

Also, server object is missing in the handler, so maybe it would make a sense to accept a function instead of the handler object to pass these props..

export async function GET({ platform, cookies }) {
  const session = cookies.get("session");
  const username = await getUsernameFromSession(session);
 
  return platform!.markForUpgrade(
    new Response('Websocket Required', {
      status: 400
    }),

    // Note the function instead of object here (proposal)..
    function handler(server) {
      return {  
         open: (ws) => {
            console.log(ws.data.username);
            server.publish("chat", `"${ws.data.username}" connected.`);
         },
         // ...
       }
    },

    // Attaching the data as the third argument (proposal)..
    {
       data: { username },
    },
  );
}

As a workaround, i could pass the data directly to my handler function and attach it to the ws object inside the handler, but still, there is no server, so i cannot do for example server.publish...

export async function GET({ platform, cookies }) {
  const session = cookies.get("session");
  const username = await getUsernameFromSession(session);
 
  return platform!.markForUpgrade(
    new Response('Websocket Required', {
      status: 400
    }),

    // a function returning current handler object..
   handler(
      // postponing the data, attaching to the `ws.data` later within `handler.open`
      {
         data: { username },
      }
    ),
  );
}

The problem with this workaround is, that the ws.data currently contains the ws handler object and typescript yelds whenever you want to customize it, moreover this approach does not solve the missing server..

[eslym]

the handler itself is already the data itself

export async function GET({ platform, cookies }) {
  const session = cookies.get("session");
  const username = await getUsernameFromSession(session);
 
  return platform!.markForUpgrade(
    new Response('Websocket Required', {
      status: 400
    }),
    {
      username,
      open(ws) {
        console.log(ws.data === this); // => true
        ws.send(`Hello ${this.username}`); // use either this.username or ws.data.username, both work
        // even `Hello ${username}` would just work since username exists in this scope
      }
    }
  );
}

if you want to avoid unwanted variable kept in the scope, here is another approach

class Greeting {
  #username: string;
  constructor(username: string) {
    this.#username = username;
  }

  open(ws) {
    ws.send(`Hello ${this.#username}`);
  }
}

export async function GET({ platform, cookies }) {
  const session = cookies.get("session");
  const username = await getUsernameFromSession(session);
 
  return platform!.markForUpgrade(
    new Response('Websocket Required', {
      status: 400
    }),
    new Greeting(username)
  );
}

Why design like this? (if you wonder)
with this approach you could easily have different kind of handler for different route, since bun only support 1 handler and need to be supplied at the very beginning

sveltekit-adapter-bun/src/files/index.ts

Line 42 in 218456f

websocket: {

[jarda-svoboda]

But, unfortunately, you still cannot access the server from the handler..

[eslym]

export function GET({ platform }) {
    console.log(platform.bunServer); // you could get bun server object from platform
}