Function normalizeLocalePath

packages/next/src/utils.ts:1869–1894

(
  pathname: string,
  locales?: string[]
)

}

export function normalizeLocalePath(
  pathname: string,
  locales?: string[]
): {
  detectedLocale?: string;
  pathname: string;
} {
  let detectedLocale: string | undefined;
  // first item will be empty string from splitting at first char
  const pathnameParts = pathname.split('/');

  (locales || []).some(locale => {
    if (pathnameParts[1].toLowerCase() === locale.toLowerCase()) {
      detectedLocale = locale;
      pathnameParts.splice(1, 1);
      pathname = pathnameParts.join('/') || '/';
      return true;
    }
    return false;
  });

  return {
    pathname,
    detectedLocale,
  };
}

export function addLocaleOrDefault(
  pathname: string,