nextjs import but don't invoke function throws Module not found: Error: Can't resolve 'dns'

The problem

This is a subtle problem with server-side code in Next.js.

The error is clear - you're trying to execute server side code (mongo query) in a client side code. But the cause is not obvious, because with Next.js you should be able to call Mongo from your components.

The cause

Next.js throws this error because you are importing your mongo code without using it.

It sounds weird but it is true.

How to avoid it

To avoid this error just remove any server-side code import in your components if you don't use it in getServerSideProps.

It sounds even more weird but it is true.

Good and bad examples

This works fine:

import { findUsers } from '../lib/queries'

function Home({ users }) {
  return (
    <h1>Users list</h1>
    //users.map and so on...
  )
}

export async function getServerSideProps() {
  const users = await findUsers()
  return {
    props: {
      users: users
    }
  }
}

export default Home

While this will throw the error:

import { findUsers } from '../lib/queries'

function Home({ users }) {
  return (
    <h1>Users list</h1>
    //users.map and so on...
  )
}

export async function getServerSideProps() {
  // call disabled to show the error
  // const users = await findUsers()
  return {
    props: {
      users: [] //returning an empty array to avoid other errors
    }
  }
}

export default Home

Keep your server-side coding modules (for e.g: models, database connection maker) outside of the Page directory.

For reference: https://nextjs.org/docs/messages/prerender-error

If you're getting this error with Next-js auth, make sure your "lib" folder is in the root directory.

Here's the structure

my problem was that i used a function in initialprops wich was exported via module.exports instead of export default

I created a directory called 'api-lib' in my project root directory to add my queries and that caused this error to appear. And I solved it by moving my 'api-lib' directory into the main 'src' directory.