FormErrorHandler.php

<?php

namespace Drupal\inline_form_errors;

use Drupal\Core\Form\FormElementHelper;
use Drupal\Core\Form\FormErrorHandler as CoreFormErrorHandler;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Link;
use Drupal\Core\Messenger\MessengerInterface;
use Drupal\Core\Render\Element;
use Drupal\Core\Render\RendererInterface;
use Drupal\Core\StringTranslation\StringTranslationTrait;
use Drupal\Core\StringTranslation\TranslationInterface;
use Drupal\Core\Url;

/**
 * Produces inline form errors.
 */
class FormErrorHandler extends CoreFormErrorHandler {
    use StringTranslationTrait;
    
    /**
     * The renderer service.
     *
     * @var \Drupal\Core\Render\RendererInterface
     */
    protected $renderer;
    
    /**
     * The messenger.
     *
     * @var \Drupal\Core\Messenger\MessengerInterface
     */
    protected $messenger;
    
    /**
     * Constructs a new FormErrorHandler.
     *
     * @param \Drupal\Core\StringTranslation\TranslationInterface $string_translation
     *   The string translation service.
     * @param \Drupal\Core\Render\RendererInterface $renderer
     *   The renderer service.
     * @param \Drupal\Core\Messenger\MessengerInterface $messenger
     *   The messenger.
     */
    public function __construct(TranslationInterface $string_translation, RendererInterface $renderer, MessengerInterface $messenger) {
        $this->stringTranslation = $string_translation;
        $this->renderer = $renderer;
        $this->messenger = $messenger;
    }
    
    /**
     * Loops through and displays all form errors.
     *
     * To disable inline form errors for an entire form set the
     * #disable_inline_form_errors property to TRUE on the top level of the $form
     * array:
     * @code
     * $form['#disable_inline_form_errors'] = TRUE;
     * @endcode
     * This should only be done when another appropriate accessibility strategy is
     * in place.
     *
     * @param array $form
     *   An associative array containing the structure of the form.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   The current state of the form.
     */
    protected function displayErrorMessages(array $form, FormStateInterface $form_state) {
        // Skip generating inline form errors when opted out.
        if (!empty($form['#disable_inline_form_errors'])) {
            parent::displayErrorMessages($form, $form_state);
            return;
        }
        $error_links = [];
        $errors = $form_state->getErrors();
        // Loop through all form errors and check if we need to display a link.
        foreach ($errors as $name => $error) {
            $form_element = FormElementHelper::getElementByName($name, $form);
            $title = FormElementHelper::getElementTitle($form_element);
            // Only show links to erroneous elements that are visible.
            $is_visible_element = Element::isVisibleElement($form_element);
            // Only show links for elements that have a title themselves or have
            // children with a title.
            $has_title = !empty($title);
            // Only show links for elements with an ID.
            $has_id = !empty($form_element['#id']);
            // Do not show links to elements with suppressed messages. Most often
            // their parent element is used for inline errors.
            if (!empty($form_element['#error_no_message'])) {
                unset($errors[$name]);
            }
            elseif ($is_visible_element && $has_title && $has_id) {
                $error_links[] = Link::fromTextAndUrl($title, Url::fromRoute('<none>', [], [
                    'fragment' => $form_element['#id'],
                    'external' => TRUE,
                ]))->toRenderable();
                unset($errors[$name]);
            }
        }
        // Set normal error messages for all remaining errors.
        foreach ($errors as $error) {
            $this->messenger
                ->addError($error);
        }
        if (!empty($error_links)) {
            $render_array = [
                [
                    '#markup' => $this->formatPlural(count($error_links), '1 error has been found: ', '@count errors have been found: '),
                ],
                [
                    '#theme' => 'item_list',
                    '#items' => $error_links,
                    '#context' => [
                        'list_style' => 'comma-list',
                    ],
                ],
            ];
            $message = $this->renderer
                ->renderInIsolation($render_array);
            $this->messenger
                ->addError($message);
        }
    }

}