Make language switcher block cacheable

Just an aside comment, this patch wasn't working for me OOTB, and what I had to do is in a custom block extending the LanguageBlock one.

Rather than using the render block, use the getCacheContexts method:

  /**
   * {@inheritdoc}
   */
  public function getCacheContexts() {
    return Cache::mergeContexts(parent::getCacheContexts(), [
      'user.permissions',
      'url.path',
      'url.query_args',
      'languages:language_content',
      'languages:language_interface',
    ]);
  }

And rather than removing the getCacheMaxAge method, override it by:

  /**
   * {@inheritdoc}
   */
  public function getCacheMaxAge() {
    return $this->cacheMaxAge;
  }

You need to include use CacheableDependencyTrait; in your custom block.

This is blocked on 🌱 Optimize render caching Needs work curretnly. But im not sure thats needed. Perhaps we can find another solution that allows us to fix this issue. That would unblock #2352009: [pp-3] Bubbling of elements' max-age to the page's headers and the page cache → more, and i feel like the whole render cache issue is a bit to big and complicated.

samit.310@gmail.com → made their first commit to this issue’s fork.