Vitest fails to run if next.config.js imports next-intl/plugin

[cupofjoakim]

Preface: I might be doing something wrong but I'm not seeing it.

I'm currently in the midst of implementing next-intl routing for a pretty large nextjs app with pages router.

Vitest is unable to run any of my 129 test suites if I import next-intl/plugin in next.config.js. It fails with this error:

TypeError: The argument 'filename' must be a file URL object, file URL string, or absolute path string. Received 'http://localhost:3000/plugin.cjs'
 ❯ Object.<anonymous> ../../node_modules/.pnpm/[email protected][email protected]_@[email protected]_@[email protected][email protected]_1328b777d3a9f794f3684dda6b7c9924/node_modules/next-intl/dist/cjs/development/plugin.cjs:90:28

This happens regardless if I call the createNextIntlPlugin() function or not.

I've followed the testing docs and added the next-intl exclusion in vitest.config.ts

/// <reference types="vitest" />

import {defineConfig} from 'vitest/config'
import react from '@vitejs/plugin-react'

export default defineConfig({
  plugins: [react()],
  test: {
    globals: true,
    testTimeout: 25000,
    include: ['./src/**/*.test.(ts|tsx)'],
    environment: 'jsdom',
    setupFiles: ['./src/__test_data__/__setup__/setup.ts'],
    css: false,
    server: {
      deps: {
        inline: ['next-intl'],
      },
    },
    deps: {
      optimizer: {
        web: {
          include: ['vitest-canvas-mock'],
        },
      },
    },
  },
})

I'm unsure if I'm missing something, but the main issue seems to be that the plugin import happening with createRequire here: https://github.com/amannn/next-intl/blob/main/packages/next-intl/src/plugin/hasStableTurboConfig.tsx#L4.

Looking at the source code, createRequire checks if document is present, and if it is, it uses document.baseUri and tries fetching plugin.cjs, which then fails. I'm confused as to where document gets defined here, considering that your examples seem to work fine and you do use jsdom in one of them.

I'm currently on the latest lts version, node 22.17.0.

Any ideas?

[cupofjoakim]

As soon as I posted I found the cause. The real issue seems to be that we import the next config into our test setup, which then would require the plugin and fail.

That being said, we still need that config for unrelated reasons, so our current workaround is this:

const createNextIntlPlugin =
  process.env.NODE_ENV === 'test' ? () => (config) => config : require('next-intl/plugin')

I'm sure this also has drawbacks, but it's clear to me that this is a code organisation issue on our end and not something to be discussed here.

I would love a better error message though, I lost quite a lot of time here.

[amannn]

Hey, thanks for posting your solution! I was going to comment the same, typically this can be resolved by making sure next-intl/plugin is only imported into your next.config.js and nowhere else.

This seems closely related: #1885 (comment)