4.3.0 Buffer is not defined

Describe the bug

After i compile app in production mode in vite (it uses rollup). I get the following error: Buffer is not defined at constants.js:5 Socket.IO client version: 4.3.0

Platform:

• Device: iMac late 2015
• OS: MacOS

Additional context

I use Vercel for compilation, but i think problem is not with Vercel

[darrachequesne]

@Murderlon I could indeed reproduce the issue, thanks a lot for the sample project 👍

This should be (finally!) fixed by https://github.com/socketio/engine.io-client/commit/9fcaf58d18c013c0b92fdaf27481f0383efb3658, included in engine.io-client@6.0.3 and socket.io-client@4.3.2 by transitivity.

Please reopen if needed.

[Murderlon]

We are running into this problem when users are building Uppy with Vite: https://github.com/transloadit/uppy/issues/3265. It’s currently blocking people from going to production.

I investigated and this seems to be a dual publishing issue. If you import socket.io-client in ESM then everything works fine. But if you are importing it indirectly through commonjs, then socket.io-client ships Buffer to the browser, which will fail.

Here is a minimal reproducible example:

vite-socketio.zip

Note: this zip includes the node_modules because I added a fake-package folder in there with a package.json and index.js.

The index.js only does this:

const io = require('socket.io-client')

module.exports = io

To see the error:

1. Download and extract zip
2. Do not run npm install
3. npm run build && npm run preview
4. See error in the console.

As this is blocking our customers I’m willing to contribute to fix this but I would need some pointers to get started. As far as I know the buffer usage comes from engine.io-client.