The way I thought to update the dropdown of the node field will not work. This should be done in this way:
https://codimth.com/blog/web/drupal/dependent-select-dropdowns-using-ajax-node-addedit-form-drupal-8-9
<?php
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Url;
/**
* Implements hook_form_alter().
*/
function MODULENAME_form_alter(&$form, FormStateInterface $form_state, $form_id)
{
if ($form_id == 'node_article_form' || $form_id == 'node_article_edit_form') {
//add wrapper to select 2
$form['field_select2']['#prefix'] = '<div id="select2-wrapper">';
$form['field_select2']['#suffix'] = '</div>';
// add ajax to select 1
$form['field_select1']['widget']['#ajax'] = [
'callback' => 'callback_field_select1_trigger',
'wrapper' => 'select2-wrapper',
'event' => 'change',
'progress' => [
'type' => 'throbber',
'message' => t('Fetching content...'),
],
];
//get select 2 options in edit form
$field_select1_value = $form_state->getValue('field_select1');
if ($form_id == 'node_article_edit_form' && !$field_select1_value) {
$field_select1_edit_value = isset($form['field_select1']['widget']['#default_value'][0]) ? $form['field_select1']['widget']['#default_value'][0] : null;
$form['field_select2']['widget']['#options'] = getSelect2Options($field_select1_edit_value);
}
}
}
/**
* @param array $form
* @param $form_state
* @return mixed
*/
function callback_field_select1_trigger(array $form, $form_state)
{
$field_select1_value = $form_state->getValue('field_select1');
if (!empty($field_select1_value)) {
$select1_value = $field_select1_value[0]['target_id'];
$form['field_select2']['widget']['#options'] = getSelect2Options($select1_value);
} else {
$form['field_select2']['widget']['#options'] = getAllSelect2Options();
}
return $form['field_select2'];
}
/**
* @param $select1_value
* @return array
*/
function getSelect2Options($select1_value)
{
$query = \Drupal::entityQuery('taxonomy_term');
$query->condition('vid', "select2_term");
$query->condition('field_select1.0.target_id', $select1_value);
$tids = $query->execute();
$terms = \Drupal\taxonomy\Entity\Term::loadMultiple($tids);
$options = [];
$options['_none'] = t('- Any -');
foreach ($terms as $key => $term) {
$options[$key] = $term->name->value;
}
return $options;
}
/**
* @return array
*/
function getAllSelect2Options()
{
$query = \Drupal::entityQuery('taxonomy_term');
$query->condition('vid', "select2_term");
$tids = $query->execute();
$terms = \Drupal\taxonomy\Entity\Term::loadMultiple($tids);
$options = [];
$options['_none'] = t('- Any -');
foreach ($terms as $key => $term) {
$options[$key] = $term->name->value;
}
return $options;
}
// example how to get options if select 1 is multiple field
$selectedItems = [];
$default_values = $form['field_select1']['widget']['#default_value'];
if ($default_values != NULL) {
foreach ($default_values as $key => $value) {
if ($value != 0) {
$selectedItems[$value] = $value;
}
}
}
if (count($tab) > 0) {
$form['field_select2']['widget']['#options'] = getSelect2Options($selectedItems);
} else {
$form['field_select2']['widget']['#options'] = getAllSelect2Options();
}