Handle defaultLocale on client router filter (#47180)
x-ref: [slack
thread](https://vercel.slack.com/archives/C03S8ED1DKM/p1678838567947919)
Follow-up to https://github.com/vercel/next.js/pull/46317. The issue is
that, if:
- `experimental.clientRouterFilter` is enabled
- `i18n` is enabled with `defaultLocale` set
- Next.js router navigates to a path that (1) is the same as
`defaultLocale` and (2) will be redirected,
then:
- **Expected:** Should hard-navigate to this path without any locale
prefix (and then redirect occurs)
- **Actual:** Hard-navigates to this path with `defaultLocale` prefix,
even though it's not needed (and then redirect occurrs)
### Solution
This PR fixes the above issue by adding `defaultLocale` to `addLocale`
which is passed to `handleHardNavigation`. [`addLocale` skips adding the
locale if `locale` is equal to
`defaultLocale`](https://github.com/vercel/next.js/blob/02125cf3b1dfba52b240fd6e0f959d896e4b6195/packages/next/src/shared/lib/router/utils/add-locale.ts#L17).
### Fixing a bug
- [x] Related issues linked using `fixes #number`
- [x] Tests added. See:
https://github.com/vercel/next.js/blob/canary/contributing/core/testing.md#writing-tests-for-nextjs
Co-authored-by: JJ Kasper <jj@jjsweb.site>
