Nested not found pages

[darklight9811]

Goals

1. allow the not found page to be scoped
2. makes next automatically trigger closest not found

Background

This complicates the life of applications that uses localization. And it differs from the error boundary behavior, making this look like a bug. And it seems counter intuitive to trigger them only on manual calls.

When there are several people complaining that this looks like a bug, I really think this should be look into.

Proposal

When there are sub not-found files in the app router directories, fallback to them instead of root one. This allows to fit them in layouts/templates/etc, enabling the full power of app router.

[Daniel4lm]

If I'm not mistaken, rendering local not-found.tsx pages was possible until ver. 13.4.9 #48227. I had to rollback from ver. 13.4.12 to 13.4.9 because of this.

[bregtemundo]

I can also confirm that rolling back to 13.4.9 fixed the not-found pages.

with later versions of next I had a lot of issues.

For my case I had a app/[locale][[..slug]]/page.jsx -> that executes the notFound function when data was not loaded.
middleware rewrote slugs to make sure the all go to locale folder.
Only when putting the not-found.tsx in app/not-found.tsx the custom error was shown.
layout.tsx from app/[locale]/.. was not on the not-found page making the styling to not be in line with the rest of the pages.
When build I got hydration errors, causing the 404 page to appear and then immediately disappear again. (This was not the case in dev mode)

[affanshahid]

It should be possible to define not-founds for nested dynamic routes. The i18n example doesn't have a root layout, the "root" layout is defined inside the [lang] param hierarchy, so the default way of doing not-found wouldn't work with the official example. This doesn't make sense