FilterTestRestrictTagsAndAttributes.php

<?php

namespace Drupal\filter_test\Plugin\Filter;

use Drupal\filter\FilterProcessResult;
use Drupal\filter\Plugin\FilterBase;
use Drupal\Component\Utility\Xss;

/**
 * Provides a test filter to restrict HTML tags and attributes.
 *
 * @Filter(
 *   id = "filter_test_restrict_tags_and_attributes",
 *   title = @Translation("Tag and attribute restricting filter"),
 *   description = @Translation("Used for testing \Drupal\filter\Entity\FilterFormatInterface::getHtmlRestrictions()."),
 *   type = Drupal\filter\Plugin\FilterInterface::TYPE_HTML_RESTRICTOR
 * )
 */
class FilterTestRestrictTagsAndAttributes extends FilterBase {
    
    /**
     * {@inheritdoc}
     */
    public function process($text, $langcode) {
        $allowed_tags = array_filter($this->settings['restrictions']['allowed'], function ($value) {
            return is_array($value) || (bool) $value !== FALSE;
        });
        return new FilterProcessResult(Xss::filter($text, array_keys($allowed_tags)));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getHTMLRestrictions() {
        $restrictions = $this->settings['restrictions'];
        // The configuration system stores FALSE as '0' and TRUE as '1'. Fix that.
        if (isset($restrictions['allowed'])) {
            foreach ($restrictions['allowed'] as $tag => $attrs_or_bool) {
                if (!is_array($attrs_or_bool)) {
                    $restrictions['allowed'][$tag] = (bool) $attrs_or_bool;
                }
                else {
                    foreach ($attrs_or_bool as $attr => $attrvals_or_bool) {
                        if (!is_array($attrvals_or_bool)) {
                            $restrictions['allowed'][$tag][$attr] = (bool) $attrvals_or_bool;
                        }
                        else {
                            foreach ($attrvals_or_bool as $attrval => $bool) {
                                $restrictions['allowed'][$tag][$attr][$attrval] = (bool) $bool;
                            }
                        }
                    }
                }
            }
        }
        if (isset($restrictions['forbidden_tags'])) {
            foreach ($restrictions['forbidden_tags'] as $tag => $bool) {
                $restrictions['forbidden_tags'][$tag] = (bool) $bool;
            }
        }
        return $restrictions;
    }

}