Client side navigation with domain locales doesn't work for localhost (and any other domain)

[javiercr]

What version of Next.js are you using?

v10.0.5 to latest version (v10.0.7-canary.6 as of today)

What version of Node.js are you using?

v12.18.3 (should be replicable in any)

What browser are you using?

Any

What operating system are you using?

Any

How are you deploying your application?

next start

Describe the Bug

When using the i18n domain routing, client-side navigation is broken when using a domain not included in the domains config, such as localhost.

The problem was probably introduced with this change included on v10.0.5:
#20562

Expected Behavior

The domain routing config should only tell Next.js what's the current locale based on the current domain. If the domain doesn't match any of the domains in the config, it should fallback to the defaultLocale and client side navigation should use that domain for any Link.

To Reproduce

Here is a codesandox using the latest v10.0.7-canary.6 next:
https://codesandbox.io/s/next-i18n-domains-client-navigation-bug-bghx7

1. Note that the config next.config.js has two domains defined (example.co.uk for en and example.es for es).
2. Note that codesandbox will run the app under a codesandbox.io subdomain. If you were running the app locally you would be running it on localhost:3000, but the problem remains the same.
3. Click on the "Go to secondary page" link.
4. Observe how the browser is requesting example.co.uk/secondary and therefore client side navigation is broken under the codesandbox domain (or any other domain running the app).

---

Here is the same codesanbox using next v10.0.4:
https://codesandbox.io/s/next-i18n-domains-client-navigation-bug-next-v10-0-4-yhs5u
Client side navigation works as expected.

[javiercr]

Note this also affects the ability to use Vercel's deployment URLs:

If we have an app that uses example.co.uk and example.es for i18n routing, client side navigation is broken for any [deployment-id].vercel.app URL, so we can't test branches and PRs with Vercel anymore.

[javiercr]

#21327 by @mokabyls seems to be related (if not the same). I'm keeping this one open as it includes a reproduction case.

[javiercr]

And #21211 by @sebastian-nowak seems to be the same too.

[ijjk]

Hi, this has been updated in the latest canary of Next.js v10.0.7-canary.7, please update and give it a try!

[javiercr]

Works perfectly, thank you!

[balazsorban44]

This issue has been automatically locked due to no recent activity. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.