TCP Socket context data is unexpectedly shared among all sockets

[xuxucode]

What version of Bun is running?

1.3.3+274e01c73

What platform is your computer?

Darwin 23.3.0 arm64 arm

What steps can reproduce the bug?

The context data is supposed to be one instance per socket, but when data: {} is passed to the Bun.listen method, the context data is shared among all sockets.

To reproduce it, run bun test-listen.ts:

test-listen.ts

import assert from 'node:assert';

type SocketData = { sessionId?: number };

Bun.listen<SocketData>({
  hostname: "localhost",
  port: 8080,
  // 1. Initialize the `data` object
  data: { },
  socket: {
    open(socket) {
      // 3. Assertion failed due to above initialized `data: {}`.
      assert.ok(socket.data.sessionId === undefined, 'initial data per socket should be undefined')
      socket.data.sessionId = Date.now();
    },
    data(socket, data) {
      const body = `${socket.data.sessionId}: ack`
      socket.write('HTTP/1.1 200 OK\r\n')
      socket.write(`Content-Length: ${body.length}\r\n`)
      socket.write("\r\n")
      socket.end(`${socket.data.sessionId}: ack`); // end connection
    },
    close(socket, err) {
      console.log('socket close:', err)
    },
    error(socket, err) {
      console.error('socket error:', err)
    }
  },
});

// 2. Sending multiple requests caused the `data` is reused.
for (let i = 0; i < 2; i++) {
  const session = await fetch('http://localhost:8080').then(res => res.text())
  console.log('session:', session)
}

Output:

What is the expected behavior?

One context data instance per socket

What do you see instead?

Context data is reused/shared

Additional information

Context data will not be shared when data: {} is not passed to Bun.listen.