HtmlTag.php

<?php

namespace Drupal\Core\Render\Element;

use Drupal\Component\Render\MarkupInterface;
use Drupal\Component\Utility\Html as HtmlUtility;
use Drupal\Core\Render\Attribute\RenderElement;
use Drupal\Core\Render\Markup;
use Drupal\Component\Utility\Xss;
use Drupal\Core\Template\Attribute;

/**
 * Provides a render element for any HTML tag, with properties and value.
 *
 * Properties:
 * - #tag: The tag name to output.
 * - #attributes: (array, optional) HTML attributes to apply to the tag. The
 *   attributes are escaped, see \Drupal\Core\Template\Attribute.
 * - #value: (string|MarkupInterface, optional) The textual contents of the tag.
 *   Strings will be XSS admin filtered.
 * - #noscript: (bool, optional) When set to TRUE, the markup
 *   (including any prefix or suffix) will be wrapped in a <noscript> element.
 *
 * Usage example:
 * @code
 * $build['hello'] = [
 *   '#type' => 'html_tag',
 *   '#tag' => 'p',
 *   '#value' => $this->t('Hello World'),
 * ];
 * @endcode
 *
 * @see \Drupal\Component\Utility\Xss::filterAdmin().
 */
class HtmlTag extends RenderElementBase {
    
    /**
     * Void elements do not contain values or closing tags.
     * @see http://www.w3.org/TR/html5/syntax.html#syntax-start-tag
     * @see http://www.w3.org/TR/html5/syntax.html#void-elements
     */
    protected static $voidElements = [
        'area',
        'base',
        'br',
        'col',
        'embed',
        'hr',
        'img',
        'input',
        'keygen',
        'link',
        'meta',
        'param',
        'source',
        'track',
        'wbr',
        'rect',
        'circle',
        'polygon',
        'ellipse',
        'stop',
        'use',
        'path',
    ];
    
    /**
     * {@inheritdoc}
     */
    public function getInfo() {
        $class = static::class;
        return [
            '#pre_render' => [
                [
                    $class,
                    'preRenderHtmlTag',
                ],
            ],
            '#attributes' => [],
            '#value' => NULL,
        ];
    }
    
    /**
     * Pre-render callback: Renders a generic HTML tag with attributes.
     *
     * @param array $element
     *   An associative array containing:
     *   - #tag: The tag name to output. Typical tags added to the HTML HEAD:
     *     - meta: To provide meta information, such as a page refresh.
     *     - link: To refer to stylesheets and other contextual information.
     *     - script: To load JavaScript.
     *     The value of #tag is escaped.
     *   - #attributes: (optional) An array of HTML attributes to apply to the
     *     tag. The attributes are escaped, see \Drupal\Core\Template\Attribute.
     *   - #value: (optional) A string containing tag content, such as inline
     *     CSS. The value of #value will be XSS admin filtered if it is not safe.
     *   - #noscript: (optional) If TRUE, the markup (including any prefix or
     *     suffix) will be wrapped in a <noscript> element. (Note that passing
     *     any non-empty value here will add the <noscript> tag.)
     *
     * @return array
     */
    public static function preRenderHtmlTag($element) {
        $attributes = isset($element['#attributes']) ? new Attribute($element['#attributes']) : '';
        // An HTML tag should not contain any special characters. Escape them to
        // ensure this cannot be abused.
        $escaped_tag = HtmlUtility::escape($element['#tag']);
        $open_tag = '<' . $escaped_tag . $attributes;
        $close_tag = '</' . $escaped_tag . ">\n";
        // Construct a void element.
        if (in_array($element['#tag'], self::$voidElements)) {
            $open_tag .= ' />';
            $close_tag = "\n";
        }
        else {
            $open_tag .= '>';
            if ($element['#value'] === NULL) {
                $element['#markup'] = '';
            }
            elseif ($element['#value'] instanceof MarkupInterface) {
                $element['#markup'] = $element['#value'];
            }
            else {
                $element['#markup'] = Markup::create(Xss::filterAdmin($element['#value']));
            }
        }
        $prefix = isset($element['#prefix']) ? $element['#prefix'] . $open_tag : $open_tag;
        $suffix = isset($element['#suffix']) ? $close_tag . $element['#suffix'] : $close_tag;
        if (!empty($element['#noscript'])) {
            $prefix = '<noscript>' . $prefix;
            $suffix .= '</noscript>';
        }
        $element['#prefix'] = Markup::create($prefix);
        $element['#suffix'] = Markup::create($suffix);
        return $element;
    }

}