How can I update the values of an exposed view filter when another filter changes value? I know there are several examples of this around, on a view with two exposed select list filters, I need to update the value of the second based on the value selected on the first. I can't even seem to get any debugging info on my callback, but the request is throwing a Drupal\Core\Form\Exception\BrokenPostRequestException. Here's the simple form alter I'm trying.

use Drupal\Core\Form\FormStateInterface;

function MODULENAME_form_alter(&amp;$form, FormStateInterface $form_state, $form_id) {
  if($form_id == "views_exposed_form"){
    $form['field_article_value1_value']['#options']  = _MODULENAME_get_update_value1_values();
    $form['field_article_value2_value']['#options']  = _MODULENAME_get_value2_values();

    $form['field_article_value1_value']['#ajax'] = [
     'callback' =&gt; ['_MODULENAME_get_value2_values_ajax_callback'],
     'event' =&gt; 'change',
     'wrapper' =&gt; 'edit-field-article-value-wrapper',
     'progress' =&gt; [
     'type' =&gt; 'throbber',
     'message' =&gt; NULL,
     ],
  ];
}

function _MODULENAME_get_value2_values_ajax_callback(array &amp;$form, FormStateInterface $form_state) : array {
  $markup = '&lt;h1&gt;Testing!&lt;/h1&gt;';
  return ['#markup' =&gt; $markup];
}
This module might help: Views Dependent Filters

If you really want a custom solution take a peek at the code there and see if it helps, or help the D8 version get released :)