NextJs Next.config.mjs import local constant file

Question

Importing local files in next.config

The issue

Hi, The issue we are facing is wanting to create a dynamic next config. This works fine when we do not import any files but when trying to import a constant file in the next.config.mjs, things break.

We are on next version 12.1 in order to use the MJS variant of the config file.

The constant file is a simple JS file with some values to determine the locales that we need to use for the different brands we support. These are used on multiple places, that is why we do not wan't to hardcode these values in here too.

import { locales } from './src/constants/locales'; // It breaks on this import

const currentPlatform = process.env.NEXT_PUBLIC_PLATFORM;

module.exports = () => ({
  i18n: {
    localeDetection: false,
    ...locales[currentPlatform],
  },
  images: {
    domains: [
      // Our domains
    ],
  },
  async rewrites() {
    return [
      // Our rewrites
    ];
  },
  webpack: (config, { defaultLoaders }) => {
    config.module.rules.push(
      // Our config
    );

    return config;
  },
});

The error message

This is the error that is thrown when we try to start the dev server, suggesting the import path is wrong. (it is not.)

error - Failed to load next.config.mjs, see more info here https://nextjs.org/docs/messages/next-config-error
Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/Users/*****/Development/****/********/src/constants/locales' imported from /Users/******/Development/******/******/next.config.mjs
Did you mean to import ../src/constants/locales.js?
    at finalizeResolution (internal/modules/esm/resolve.js:276:11)
    at moduleResolve (internal/modules/esm/resolve.js:699:10)
    at Loader.defaultResolve [as _resolve] (internal/modules/esm/resolve.js:810:11)
    at Loader.resolve (internal/modules/esm/loader.js:86:40)
    at Loader.getModuleJob (internal/modules/esm/loader.js:230:28)
    at ModuleWrap.<anonymous> (internal/modules/esm/module_job.js:56:40)
    at link (internal/modules/esm/module_job.js:55:36) {
  code: 'ERR_MODULE_NOT_FOUND'
}

• = Censored pathnames

Any tips, tricks or extra info is welcome!

Thanks in advance.

Answer 1

Perhaps you are using .vercelignore and not include the file/folder. I made the same mistake, in my case I not included ./lingui.config.js .

> Build error occurred
Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/vercel/path0/lingui.config.js' imported from /vercel/path0/next.config.mjs
    at new NodeError (internal/errors.js:322:7)
    at moduleResolve (internal/modules/esm/resolve.js:731:10)
    at Loader.defaultResolve [as _resolve] (internal/modules/esm/resolve.js:842:11)
    at Loader.resolve (internal/modules/esm/loader.js:89:40)
    at Loader.getModuleJob (internal/modules/esm/loader.js:242:28)
    at ModuleWrap.<anonymous> (internal/modules/esm/module_job.js:76:40)
    at link (internal/modules/esm/module_job.js:75:36) {
code: 'ERR_MODULE_NOT_FOUND'
}

To fix, I add the missing file:

/*

!/public
!/src
!/lingui.config.js # <-- my mistake
!/next-env.d.ts
!/next.config.mjs
!/package.json
!/postcss.config.js
!/tailwind.config.cjs
!/tsconfig.json
!/yarn.lock

Answer 2

I had the same issue using nextjs v13.x and I was able to successfully import my:

import { var1, var2 } from './src/constants.js

with a standard js module written in the constants file.

const var1 = 'hello'; const var2 = 'world'; module.exports = { var1, var2 };