class TaxonomyIndexTidDepth

class TaxonomyIndexTidDepth extends TaxonomyIndexTid {
    use TaxonomyIndexDepthQueryTrait;
    public function operatorOptions($which = 'title') {
        return [
            'or' => $this->t('Is one of'),
        ];
    }
    protected function defineOptions() {
        $options = parent::defineOptions();
        $options['depth'] = [
            'default' => 0,
        ];
        return $options;
    }
    public function buildExtraOptionsForm(&$form, FormStateInterface $form_state) {
        parent::buildExtraOptionsForm($form, $form_state);
        $form['depth'] = [
            '#type' => 'weight',
            '#title' => $this->t('Depth'),
            '#default_value' => $this->options['depth'],
            '#description' => $this->t('The depth will match nodes tagged with terms in the hierarchy. For example, if you have the term "fruit" and a child term "apple", with a depth of 1 (or higher) then filtering for the term "fruit" will get nodes that are tagged with "apple" as well as "fruit". If negative, the reverse is true; searching for "apple" will also pick up nodes tagged with "fruit" if depth is -1 (or lower).'),
        ];
    }
    public function query() {
        // If no filter values are present, then do nothing.
        if (count($this->value) == 0) {
            return;
        }
        elseif (count($this->value) == 1) {
            // Sometimes $this->value is an array with a single element so convert it.
            if (is_array($this->value)) {
                $this->value = current($this->value);
            }
        }
        // The normal use of ensureMyTable() here breaks Views.
        // So instead we trick the filter into using the alias of the base table.
        // See https://www.drupal.org/node/271833.
        // If a relationship is set, we must use the alias it provides.
        if (!empty($this->relationship)) {
            $this->tableAlias = $this->relationship;
        }
        else {
            $this->tableAlias = $this->query
                ->ensureTable($this->view->storage
                ->get('base_table'));
        }
        $this->addSubQueryJoin($this->value);
    }

}