Error: Can't resolve 'uws'

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Current behaviour

I use socket.io, therefore engine.io is one of my depended packages. When I try to bundle my project, I have error Module not found: Error: Can’t resolve ‘uws’ in node_modules/engine.io/lib/server.js (The error would not be here if I configure webpack with webpack-node-externals, but I really need all packages in a single bundle for docker container.)

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

1. Add socket.io v2.2.0 to your existing project (which uses webpack) as a production dependency.
2. Require it in your entry point code.
3. Run webpack

Expected behaviour

It should create a bundle without errors.

Setup

• OS: centOS
• browser: server side (node.js)
• engine.io version: 3.3.2

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

IMO it could be fixed if engine.io declares uws as a prod dependency (not a dev dependency).

[Domiii]

If you are here because your webpack build fails - good news: There is an easy fix!

Problem Explanation

In recent socket.io versions, ws is already set as the default wsEngine. So unless you actually want to use uws, you don’t have to worry about it at all because engine.io won’t even require it in that case.

However, webpack does not know that. It only sees the dependency in the code, it sees require('uws'), and, not knowing that that part of the code will never execute, it will try to bundle it nevertheless.

Solution

Simply tell it to not bundle it by adding uws to your externals in your webpack.config and you are done 😃

E.g.:

module.exports = {
  // ...
  externals: { 
     uws: 'uws' 
  }
};

[mmdevries]

@sethcwhiting unfortunately this version doesn’t work with node 10 and higher. At least if you want to use a secure connection(wss). We didn’t want to step over to the javascript ws package and we created a new uws package and added support for node 10 and node 12. This new package is based on the original uws and we merged some fixes from cws. Maybe this will be useful for others as well.

https://github.com/mmdevries/uws