4.3.0 Buffer is not defined

[faradaytrs]

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]

Arf, now that the dev build is fixed (socketio/engine.io-client@4971914), it's the production build that fails... I'm digging into this.

[darrachequesne]

It should be fixed in latest version (4.3.1), could you please check?

[faradaytrs]

Nope it's still the same. And error is in runtime, not during the build.

[darrachequesne]

@faradaytrs I cannot reproduce with latest version: https://github.com/socketio/socket.io-fiddle/tree/vite

Could you please check?

[tcastelly]

Hello,

I had the same issue even after the fix (4.3.2).
It was my fault;

I use socket.io-client in a third party library. This library has socket.io-client as peerDependencies. I have two builds:

• my-lib.es.js
• my-lib.umd.js

My main project used the umd instead of the es, after change to use the es it works!

The repo to reproduce.

[faradaytrs]

I have similar situation with @tcastelly, but my dependency doesn't have esm build. It relies on socket.io-client as peer dependency though.

[faradaytrs]

After I updated dep to use esm it works, but I believe it might be a problem in many cases for many people.

[Murderlon]

We are running into this problem when users are building Uppy with Vite: transloadit/uppy#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.

[darrachequesne]

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

This should be (finally!) fixed by socketio/engine.io-client@9fcaf58, included in engine.io-client@6.0.3 and socket.io-client@4.3.2 by transitivity.

Please reopen if needed.