I'd like to add a couple classes to the "Read more" and "Add new comment" links in my article teasers in Drupal 8.

I'd do this in Drupal 7 by doing something like this in my theme file:

function mytheme_preprocess_node(&$variables) {
  $variables['content']['links']['node']['#links']['node-readmore']['attributes']['class'][] = 'btn btn-primary';
  $variables['content']['links']['node']['#links']['comment-add']['attributes']['class'][] = 'btn btn-primary';
}

But this doesn't work in Drupal 8. I dumped the contents of $variables['content']['links'] and all I got was this:

$variables['...']['...'] array(2)
    '#lazy_builder' => array(2)
        string(40) "Drupal\node\NodeViewBuilder::renderLinks"
        array(4)
            string(1) "4"
            string(6) "teaser"
            string(2) "en"
            boolFALSE
    '#weight' => integer100

So how would I go about adding classes to these links in Drupal 8?

I'd like to add a couple classes to the "Read more" and "Add new comment" links in my article teasers in Drupal 8.

I'd do this in Drupal 7 by doing something like this in my theme file.

function mytheme_preprocess_node(&$variables) {
  $variables['content']['links']['node']['#links']['node-readmore']['attributes']['class'][] = 'btn btn-primary';
  $variables['content']['links']['node']['#links']['comment-add']['attributes']['class'][] = 'btn btn-primary';
}

But this doesn't work in Drupal 8. I dumped the contents of $variables['content']['links'] and all I got was this:

$variables['...']['...'] array(2)
    '#lazy_builder' => array(2)
        string(40) "Drupal\node\NodeViewBuilder::renderLinks"
        array(4)
            string(1) "4"
            string(6) "teaser"
            string(2) "en"
            boolFALSE
    '#weight' => integer100

So how would I go about adding classes to these links in Drupal 8?