This fixes the prefetching handling when middleware is present as currently we are incorrectly triggering data requests for non-SSG pages to handle the case where a middleware rewrite is present and pointing to an SSG path. Since the majority use case won't be rewriting in middleware and this incurs a lot of potentially heavy requests to `getServerSideProps` paths this matches the prefetch handling when middleware isn't present and only prefetches the data route when we match an SSG path.
Fixes: [slack thread](https://vercel.slack.com/archives/C0289CGVAR2/p1661364670589519?thread_ts=1661199566.675759&cid=C0289CGVAR2)
Fixes: https://github.com/vercel/next.js/issues/38918
## Bug
- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`
This PR fixes an issue where we have a middleware that rewrites every single request to the same origin while having `i18n` configured. It would be something like:
```typescript
import { NextResponse } from 'next/server'
export function middleware(req) {
return NextResponse.rewrite(req.nextUrl)
}
```
In this case we are going to be adding always the `locale` at the beginning of the destination since it is a rewrite. This causes static assets to not match and the whole application to break. I believe this is a potential footgun so in this PR we are addressing the issue by removing the locale from pathname for those cases where we check against the filesystem (e.g. public folder).
To achieve this change, this PR introduces some preparation changes and then a refactor of the logic in the server router. After this refactor we are going to be relying on properties that can be defined in the `Route` to decide wether or not we should remove the `basePath`, `locale`, etc instead of checking which _type_ of route it is that we are matching.
Overall this simplifies quite a lot the server router. The way we are testing the mentioned issue is by adding a default rewrite in the rewrite tests middleware.
* Update to process redirects/rewrites for _next/data
* correct matched-path resolving with middleware
* Add next-data header
* migrate middleware tests
* lint-fix
* update error case
* update test case
* Handle additional resolving cases and add more tests
* update test from merge
* fix test
* rm .only
* apply changes from review
* ensure _next/data resolving does not apply without middleware
