Middleware enhancements after new Next.js middleware architecture

[amannn]

Is your feature request related to a problem? Please describe.

It seems like there's work happening on the Next.js side on a middleware revamp: vercel/next.js#46722 (comment)

I'm using this thread to collect aspects about the current next-intl middleware that we could potentially address in case a revamp is relevant after the Next.js change.

Describe the solution you'd like

My personal wishlist for Next.js:

1. Passing a locale to the rendering phase (see Reading params deeply in Server Components (e.g. for i18n / multi-tenancy) vercel/next.js#58862). Ideally this would be possible without a middleware in the first place though.
2. A dynamically created matcher

Mentioned both here.

Separately from this, there are some use cases we could support better that do not rely on Next.js:

1. Get the locale within middleware #1356
2. Locale detection could be more flexible #1369
3. Maybe opting out of root-redirect? Possibly already by adapting the matcher, but would there be an advantage to make this more explicit?
4. Should the middleware automatically decide if a request should be handled or not (see example from docs), allowing us to remove the default matcher? (might need an option to opt-out) We'd only be able to do it for the localePrefix: 'always' case though (and only if the user doesn't want to automatically redirect /users → /en/users). Is this helpful?

We can make these changes in any case, but in case a refactoring is necessary after the Next.js change, maybe it'd be worth waiting a bit.

[amannn]

Seems like there's some movement here: vercel/next.js#70961.

As far as I understand the feature, it's mostly targeted at validation. The best I can think of is a validation that the [locale] param contains a valid value and alternatively call notFound(). This would be a slight improvement, but if the mere presence of an interceptor opts the page into dynamic rendering, this already has a downside in comparison to running the validation in [locale]/layout.tsx.

From a first glance, the new interceptors feature currently doesn't look like it could help with the pain points that were mentioned above. I'll keep an eye on it though.