Issue #2710283 by BR0kEN: Adapting views filter

<?php

/**

 * @file

 * Definition of shs_handler_filter_term_node_tid.

 */

namespace Drupal\cshs\Plugin\views\filter;

use Drupal\Core\Form\FormStateInterface;

use Drupal\taxonomy\Plugin\views\filter\TaxonomyIndexTid;

/**

 * Filter by term id (including selection by client-side hierarchical select).

 * Filter by term id.

 *

 * @ingroup views_filter_handlers

 *

 * @ViewsFilter("cshs_node_tid")

 */

class CshsNodeTid extends TaxonomyIndexTid {

  const ID = 'cshs';

  /**

   * {@inheritdoc}

   */

class cshs_handler_filter_term_node_tid extends views_handler_filter_term_node_tid {

  public function adminSummary() {

    // Set up $this->value_options for the parent summary.

    $this->valueOptions = [];

    if ('All' === $this->value) {

      $this->value = NULL;

    }

  function option_definition() {

    $options = parent::option_definition();

    return parent::adminSummary();

  }

  /**

   * {@inheritdoc}

   */

  public function defineOptions() {

    $options = parent::defineOptions();

    $options['type'] = array('default' => 'cshs');

    $options['type'] = ['default' => static::ID];

    return $options;

  }

  function extra_options_form(&$form, &$form_state) {

    parent::extra_options_form($form, $form_state);

  /**

   * {@inheritdoc}

   */

  public function buildExtraOptionsForm(&$form, FormStateInterface $form_state) {

    parent::buildExtraOptionsForm($form, $form_state);

    $form['type']['#options'] += array(

      'cshs' => t('Client-side hierarchical select'),

    );

    $form['type']['#options'] += [

      static::ID => t('Client-side hierarchical select'),

    ];

  }

  function value_form(&$form, &$form_state) {

    global $language;

  /**

   * {@inheritdoc}

   */

  public function valueForm(&$form, FormStateInterface $form_state) {

    parent::valueForm($form, $form_state);

    parent::value_form($form, $form_state);

    $vocabulary = \Drupal::entityTypeManager()

      ->getStorage('taxonomy_vocabulary')

      ->load($this->options['vocabulary']);

    $multiple = $this->options['expose']['multiple'];

    $vocabulary = taxonomy_vocabulary_machine_name_load($this->options['vocabulary']);

    if (empty($vocabulary) && $this->options['limit']) {

      $form['markup'] = array(

      $form['markup'] = [

        '#markup' => '<div class="form-item">' . t('An invalid vocabulary is selected. Please change it in the options.') . '</div>',

      );

      ];

      return;

    }

    if ($this->options['type'] == 'cshs' && $this->options['exposed']) {

      $identifier = $this->options['expose']['identifier'];

      $form['value']['#type'] = 'cshs';

    if (static::ID === $this->options['type'] && $this->options['exposed']) {

      $form['value']['#type'] = $this->options['type'];

      //cshs_prepare_form_element($form['value']);

      // TODO disable the option in the views settings to allow multiple selections.

      // TODO test if default value works...

    }

    if (empty($form_state['exposed'])) {

      // Retain the helper option.

      $this->helper->options_form($form, $form_state);

    }

  }

  function admin_summary() {

    // Set up $this->value_options for the parent summary.

    $this->value_options = array();

    if ($this->value == 'All') {

      $this->value = NULL;

      $this->helper->buildOptionsForm($form, $form_state);

    }

    return parent::admin_summary();

  }

}