next build fails with ERR_MODULE_NOT_FOUND - Works in 11.x but not in 12.x

[lionelhorn]

What version of Next.js are you using?

12.0.4

What version of Node.js are you using?

17.0.1

What browser are you using?

Chrome

What operating system are you using?

Windows

How are you deploying your application?

next build

Describe the Bug

next build erros with a Module not found

info  - Creating an optimized production build  
info  - Compiled successfully

> Build error occurred
Error [ERR_MODULE_NOT_FOUND]: Cannot find module 'C:\PROG\Issues\issues-nextjs-deepkit\node_modules\@deepkit\type\dist\esm\src\types' imported from C:\PROG\Issues\issues-nextjs-deepkit\node_modules\@deepkit
\type\dist\esm\index.js
    at new NodeError (node:internal/errors:371:5)
    at finalizeResolution (node:internal/modules/esm/resolve:394:11)
    at moduleResolve (node:internal/modules/esm/resolve:915:10)
    at defaultResolve (node:internal/modules/esm/resolve:1005:11)
    at ESMLoader.resolve (node:internal/modules/esm/loader:475:30)
    at ESMLoader.getModuleJob (node:internal/modules/esm/loader:245:18)
    at ModuleWrap.<anonymous> (node:internal/modules/esm/module_job:79:40)
    at link (node:internal/modules/esm/module_job:78:36) {
  type: 'Error',
  code: 'ERR_MODULE_NOT_FOUND'
}

Expected Behavior

A proper successful build.

To Reproduce

I created a repo with 2 branches and steps.

next 11.x branch : Building correctly
next 12.x branch : Building fails

https://github.com/lionelhorn/issues-nextjs-deepkit

[balazsorban44]

Adding this to next.config.js

experimental: {
  esmExternals: false,
},

Fixes this temporarily.

Seems to be related to https://nextjs.org/blog/next-12#es-modules-support-and-url-imports

I'll try to look more into this.

Here is a related thread: #27876

[lionelhorn]

Thanks @balazsorban44 for the info and links.
It fixes the initial issue :)

[balazsorban44]

I looked at the module that is failing. @deepkit/type

Adding .js to the imports and exports in its files under dist/esm seems to help.

Might be because of: https://nodejs.org/api/esm.html#mandatory-file-extensions

In that case, maybe that dependency is packaged incorrectly and Next.js was good at masking the issue in previous versions but is more strict about it in newer ones? 🤔

[balazsorban44]

So yes. My assumption seems to be correct. This applies: https://nodejs.org/api/esm.html#mandatory-file-extensions

Next.js 12 defaults esmExternals to true. That means it will treat node_modules as ESM instead of Common.js, when available. node_modules are directly loaded by Node.js and not bundled, so the Node.js ESM guidelines apply.

This means you will have to take it up with the @deepkit developers so they can fix their package distribution accordingly.

[balazsorban44]

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