ViewsExposedFilterBlock.php

<?php

namespace Drupal\views\Plugin\Block;

use Drupal\Core\Cache\Cache;
use Drupal\Component\Utility\Xss;

/**
 * Provides a 'Views Exposed Filter' block.
 *
 * @Block(
 *   id = "views_exposed_filter_block",
 *   admin_label = @Translation("Views Exposed Filter Block"),
 *   deriver = "Drupal\views\Plugin\Derivative\ViewsExposedFilterBlock"
 * )
 */
class ViewsExposedFilterBlock extends ViewsBlockBase {
    
    /**
     * {@inheritdoc}
     */
    public function getCacheContexts() {
        $contexts = $this->view->display_handler
            ->getCacheMetadata()
            ->getCacheContexts();
        return Cache::mergeContexts(parent::getCacheContexts(), $contexts);
    }
    
    /**
     * {@inheritdoc}
     *
     * @return array
     *   A renderable array representing the content of the block with additional
     *   context of current view and display ID.
     */
    public function build() {
        $output = $this->view->display_handler
            ->viewExposedFormBlocks();
        // Provide the context for block build and block view alter hooks.
        // \Drupal\views\Plugin\Block\ViewsBlock::build() adds the same context in
        // \Drupal\views\ViewExecutable::buildRenderable() using
        // \Drupal\views\Plugin\views\display\DisplayPluginBase::buildRenderable().
        if (is_array($output) && !empty($output)) {
            $output += [
                '#view' => $this->view,
                '#display_id' => $this->displayID,
            ];
        }
        // Before returning the block output, convert it to a renderable array with
        // contextual links.
        $this->addContextualLinks($output, 'exposed_filter');
        // Set the blocks title.
        if (!empty($this->configuration['label_display']) && ($this->view
            ->getTitle() || !empty($this->configuration['views_label']))) {
            $output['#title'] = [
                '#markup' => empty($this->configuration['views_label']) ? $this->view
                    ->getTitle() : $this->configuration['views_label'],
                '#allowed_tags' => Xss::getHtmlTagList(),
            ];
        }
        return $output;
    }

}