Bug in remove-default-locale Branch - Locale Switching Issue

[Villalobos4113]

Bug in remove-default-locale Branch - Locale Switching Issue

Environment:

• Branch: remove-default-locale
• Browser's Default Locale: en
• Project's Default Locale: de

Description:
There appears to be a bug affecting locale switching functionality. When the browser's default locale is set to English ('en') and the project's default locale is set to German ('de'), the following issue occurs:

Steps to Reproduce:

1. Open the application with the browser's default locale set to 'en'.
2. The first render redirects to '/en' (expected behavior).
3. Attempt to switch to the German locale ('de') using the provided button.

Expected Behavior:
Upon clicking the switch button, the application should redirect to the '/de' route.

Actual Behavior:
The button does not work as intended. The redirectedPathName becomes '/' and the middleware interprets this as if no locale is found, resulting in a redirect back to the user's default locale ('en'). Consequently, switching to '/de' via the button is not possible.

[HamedBahram]

I cannot reproduce this issue. It works as intended on the main and the remove-default-locale branches.

• main branch → https://next-i18n-ten.vercel.app/en
• remove-default-locale branch → https://next-i18n-f6m6ol5u8-hamedbahram.vercel.app/

[Villalobos4113]

@HamedBahram Hey, sorry for the late response. For you to reproduce the error, the project's default locale should be set to "de", and your browser's default locale to "en". If you can't reproduce the error let me know so I can send you a screen recording of what I'm experiencing. Thank you

[Villalobos4113]

Also, you can reproduce the error keeping the project's default locale in "en" but switching your browser's default locale to "de"

[sorcerb]

Hey, sorry for the late response.

Make defaultLocale not en, or browser local not en.

getLocale - function must be removed, because we are not interested in browser settings
We need rewrite if no local in path
And redirect if default local in path

import { NextResponse } from 'next/server';
import type { NextRequest } from 'next/server';
import { i18n } from '@/i18n.config';

export function middleware(request: NextRequest) {
    const pathname = request.nextUrl.pathname;
    const pathnameIsMissingLocale = i18n.locales.every(
        locale => !pathname.startsWith(`/${locale}/`) && pathname !== `/${locale}`
    )

    // Rewrite if there is no locale
    const locale = i18n.defaultLocale;
    if (pathnameIsMissingLocale) {
        if (locale === i18n.defaultLocale) {
            return NextResponse.rewrite(new URL(`/${locale}${pathname.startsWith('/') ? '' : '/'}${pathname}`,
                request.url));
        }
    }

    // Redirect to remove default locale prefix
    if (pathname.startsWith(`/${locale}`)) {
        return NextResponse.redirect(new URL(`${pathname.replace(new RegExp(`^/${locale}`), '')}`,
            request.url));
    }

}

export const config = {
    // Matcher ignoring `/_next/` and `/api/`
    matcher: ['/((?!api|_next/static|_next/image|favicon.ico).*)']
}