Add support for subdomain routing

As i18next-browser-languageDetector supports subdomain detection out of the box, it’d be nice to also support it here.

We would have two mutually exclusive options regarding routing:

1. localeSubpaths (already exists)
2. localeSubdomains (does not exist)

Or perhaps we’d have a single localeRouting option that would take an enum of strings, eg subpaths or subdomains.

We’d need to add logic to lng-path-corrector and lng-path-detector to handle subdomains instead of subpaths.

We’d also need to update the Link component.

I don’t yet know how feasible this proposal is, as it’s not possible to have a SPA across subdomains anyways. Development and testing will also be a pain.

[lucasfeliciano]

Hey @HeadFox, here is my implementation of my detector

languageByDomainDetector.js

const getLanguageFromHostname = require('./getLanguageFromHostname')

module.exports = {
  name: 'domain',

  lookup(req, res, options) {
    let language = 'en'

    if (typeof window !== 'undefined' ) {
      language = getLanguageFromHostname(window.location.hostname)
    } else {
      language = getLanguageFromHostname(req.get('host'))
    }

    return language
  },

  cacheUserLanguage(req, res, language, options = {}) {
    //todo
  },
}

The getLanguageFromHostname is a helper that I have a map of my domains which is mapped to a certain language

And when creating the next-i18next instance you pass like this:

const NextI18NextInstance = new NextI18Next({
  defaultLanguage: 'en',
  fallbackLng: 'en',
  otherLanguages: ['nl', 'de', 'fr', 'hu', 'es'],
  load: 'languageOnly',
  customDetectors: [languageByDomainDetector], // <- Add the domain detector as a custom detector
  detection: {
    order: ['domain'], // <- Say to i18n to use the domain detector
  },
})

[isaachinman]

When changing languages in the localeSubpaths approach, for example, we can maintain full SPA navigation. That is to say, a router event happens within NextJs and a new chunk/page and namespaces will be loaded, but are no new document requests or hard navigation.

That is not possible over subdomains - you are forced to basically serve two completely different webpages. You might as well have static React apps, or just forcefully set the locale and don’t allow changing.