External modules are not packaged with webpack 5

This is a Bug Report

Description

Since updating to the release version of webpack 5, it seems like external modules are no longer packaged. I investigated a bit and in packExternalModules#getExternalModules I don’t see the externals I specify in my webpack config. I checked webpack 5 release notes but could not find a not about that and how to fix it. As a workaround I was able to use stats.compilation.modules instead of chunks and it does include the externals. Not sure if this is a proper fix though.

Similar or dependent issue(s): N/A

Additional Data

• Serverless-Webpack Version you’re using: 5.3.5
• Webpack version you’re using: 5.1.3
• Serverless Framework Version you’re using: 2.8.0
• Operating System: MacOS 10.15.7
• Stack Trace (if available): N/A

[maxholman]

I was able to work around this by disabling optimization.concatenateModules (defaults to true in production mode)

[PaulContremoulin]

Same issue related, as @maxholman mentions, this configuration :

optimization: {
        // fix node modules not packaged into zip
        concatenateModules: false
    },

work for me !