Allow non-root not-found to be passed down from its own segment until the next not-found

[devjiwonchoi]

Goals

Option 1

Allow non-root not-found to be passed down from its own segment until the next not-found.

Option 2 ❌

Explicitly support i18n not-found, with declared parent dir name [lang].
If the project has [lang], app/[lang]/not-found will be treated as global.
Should consider route groups also.

Option 3 ❌

Let global not-found to receive the context.params.slug (lang) in order to set the translation by lang.
I'm assuming this won't work since it's on the root.

Non-Goals

It should not interfere with any other routing.

Background

Say in i18n, the project needs an i18n supported not-found, which probably needs to be within the app/[lang] segment.

Since the non-root not-found is confined to predefined routes, the invalid URL is going to show a default 404 page if no root not-found is set.

The current possible DX is to set a not-found file on every segment or set a global not-found without i18n support.

In multiple root group routes without root layout on app, they won't have any root not-founds.

Proposal

I am willing to contribute.