Impossible to use next-intl with Turbopack dev flag

[joshverd]

Description

It seems like using the --turbo flag with the Nextjs dev server is currently not possible. There appears to be a mismatch with how the config file is resolved at different points in the dev server operation.

If I start the Next dev server without --turbo and the following config, everything works great:

/**
 * This works for Webpack
 * 
 * But NOT for starting the Turbo dev server
 */
const withNextIntl = createNextIntlPlugin(
  'i18n/request.ts',
);

But this does NOT work with turbo:

Error: [next-intl] Could not find i18n config at i18n/request.ts, please provide a valid path.

Second, I tried setting up another config file path, starting from src/ this time:

/**
 * This works for STARTING the Turbo dev server
 * 
 * But this will throw an error in layout.tsx when loading localhost:3000
 */
const withNextIntl = createNextIntlPlugin(
  'src/i18n/request.ts',
);

The dev server starts just fine, but once I load the project in the browser it throws an error in layout.tsx:

 ✓ Compiled / in 1295ms
 ⨯ Error: Couldn't find next-intl config file. Please follow the instructions at https://next-intl.dev/docs/getting-started/app-router
    at RootLayout (src/app/layout.tsx:20:31)
  18 |   children: React.ReactNode
  19 | }) {
> 20 |   const locale = await getLocale();

This could be related to how I structure my projects. All Nextjs frontend code is contained within the src/ dir. Check package.json in the repro repository to see the scripts I am using to start Next.

Verifications

• I've verified that the problem I'm experiencing isn't covered in the docs.
• I've searched for similar, existing issues on GitHub and Stack Overflow.
• I've compared my app to a working example to look for differences.

Mandatory reproduction URL

https://github.com/joshverd/next-intl-bug-repro

Reproduction description

1. Clone repro repository
2. Run npm i
3. Open src/next.config.ts
4. Run npm run dev-turbo

Expected behaviour

I expect the dev server to 1) start properly and 2) render my layout.tsx and page.tsx files correctly.

[amannn]

It seems like there are the following issues here:

1. The path to i18n/request.ts needs to be relative (e.g. ./src/i18n/request.ts) or simply removed (since you use the default)
2. The [directory] option for next dev doesn't work properly, you can resolve this by moving next.config.ts one folder up and calling next dev --turbo instead

I think what next-intl could do better is:

1. Consistently handle relative paths (currently your input passes the validation but fails at runtime)
2. Maybe support the [directory] option (I didn't even know this was supported, it's the first time I saw it)

But with the steps mentioned above you should be able to work around the issue for now.

[joshverd]

Gotcha, that makes sense. I really appreciate the help here!

I tried digging through the next-intl code and debugging but I think Turbopack strips out any logging from node modules, which made it extremely difficult.