[Docs]: `createMessagesDeclaration` on `next dev` won't output anymore

[icyJoseph]

Link to page

https://next-intl.dev/docs/workflows/typescript#messages-arguments

Describe the problem

Hi,

As of next@canary (since v15.5.1-canary.0), next dev, the way it is done in next-intl, won't generate createMessagesDeclaration. This is because the config is no longer loaded within next-dev, but within server-start.

next-intl/packages/next-intl/src/plugin/createMessagesDeclaration.tsx

Lines 17 to 23 in 1de05a2

	const shouldRun = [
	'dev',
	'build',
	'typegen'
	// Note: The 'lint' task doesn't consult the
	// Next.js config, so we can't detect it here.
	].some((arg) => process.argv.includes(arg));

So the dev arg is no longer visible.

Just opening this issue to document this. I do believe next typegen is more correct to generate such types, but yeah, people only running next dev.

To verify:

pnpm create next-app -e https://github.com/amannn/next-intl/tree/main/examples/example-app-router next-intl-app-router

Then install next@canary, and see that the messages folder doesn't have the .d.json.ts file.

[amannn]

Hey, thanks a lot for the heads-up here @icyJoseph!

I've set up #2008 to address this. I know it's not ideal having to make these kind of detections but the new one should be safer.

Just out of curiosity: How did you encounter this? Are you using next-intl somewhere?

[icyJoseph]

No worries - for transparency, I was trying to fully understand the usePathname + pre-rendering + rewrites, issue, by looking at real use cases, to try and improve the docs on this matter (the current note about this in the next.js docs is a bit too small/easy to miss)

So I was looking at how next-intl does what it does, and found the dev check. I've also found another library that relied on this, so it was still fresh on my memory.

That's s nice fix though!

[amannn]

Got it! You mean vercel/next.js#73085, right? It might be best to look at it from a practical use case, there's already some mitigation for this (ref).

If there's anything I can help with, like discussing implementation details, please just let me know. I'm also available on your company Slack for quick chats / calls!

Really appreciate you reaching out here proactively! 🙏