Strange bug when sending an object with an async method call to a room

[brandoncollins7]

You want to:

• report a bug
• request a feature

Current behaviour

When including an async method call as a property to the emit object, the send goes to everyone regardless of if they are in the room or not.

Steps to reproduce (if the current behaviour is a bug)

Not working:

    let pairs = await db('currency_pairs')
    await Promise.all(
        pairs.map(async p => {
            socket.to(`orderbook-${p.id}`).emit('orderbook', {
                orderbook: await orderbook_service.getOrderbook(p.id),
                pairId: p.id
            })
        })
    )

Working:

    let pairs = await db('currency_pairs')
    await Promise.all(
        pairs.map(async p => {
            let orderbook = await orderbook_service.getOrderbook(p.id)
            socket.to(`orderbook-${p.id}`).emit('orderbook', {
                orderbook,
                pairId: p.id
            })
        })
    )

Expected behaviour

What is expected?

emit should only send to users which have been joined to the room

Setup

• OS: Windows - Node.js
• browser:
• socket.io version:
  2.3.0

Other information (e.g. stacktraces, related issues, suggestions how to fix)

[darrachequesne]

Duplicate of #3431

Added in the documentation here, until we fix this behavior in Socket.IO v4.