Add the language in the exported Metadata object for SSR for a page

[fabien-h]

Goals

Easier setup for i18n and document metadata in SSR.

Non-Goals

No response

Background

There is a possible workaround with a middleware but this is super annoying to manage for something that should be super simple.

Proposal

I'm not sure but I would go threre :

https://github.com/vercel/next.js/blob/afddb6ebdade616cdd7780273be4cd28d4509890/packages/next/src/pages/_document.tsx#LL1193C12-L1193C12

If we have

export const metadata: Metadata = {
  title: 'My title',
  htmlLang: 'en-US',
};

Inject it in the props as the first element tested in the conditionnal.

From what I understand from this :

next.js/packages/next/src/pages/_document.tsx

Line 677 in afddb6e

} = this.context

The Head function and the Html function share the same context. The head metada available in the context should be available for both.

I know that head tags and html attributes are not the same kind of things. But from a user perspective, they land in the same category of the general document metadata things.