Error when adding a dot to the first segment in url

[ninnjak]

Description

I'm facing the same issue outlined here: #307

I have an application that uses the first segment for user profiles e.g. (http://localhost:3000/username) when the username contains a dot (http://localhost:3000/username.username) it attempts to pass username.username as the locale instead of the default locale. It works with all other locales when explicitly set in the url.

Mandatory reproduction URL (CodeSandbox or GitHub repository)

https://codesandbox.io/p/sandbox/inspiring-sun-2fsrpw

Reproduction description

Steps to reproduce:

1. Open reproduction
2. Navigate to /username.username
3. Returns 404 page

Expected behaviour

The url should be resolved using the default locale

[amannn]

The reason why you're encountering this issue is that your middleware matcher excludes anything that contains a dot.

You can fix this by adjusting the matcher, but be careful that you're still excluding anything that is not a content route (e.g. favicon.ico, etc.). You could consider adding all static assets to a folder like ./public/assets and then exclude that one from the middleware:

export const config = {
  matcher: ["/((?!api|_next|assets).*)"],
};

Working demo: https://codesandbox.io/p/sandbox/youthful-haibt-xp92kh?file=/middleware.ts:15,1-17,3

I'll move this to a discussion since it's more a usage question than a bug report.