class ContextualTestHooks

class ContextualTestHooks {
    
    /**
     * Implements hook_block_view_alter().
     */
    public function blockViewAlter(array &$build, BlockPluginInterface $block) {
        $build['#contextual_links']['contextual_test'] = [
            'route_parameters' => [],
        ];
    }
    
    /**
     * Implements hook_contextual_links_view_alter().
     *
     * @todo Apparently this too late to attach the library?
     * It won't work without contextual_test_page_attachments_alter()
     * Is that a problem? Should the contextual module itself do the attaching?
     */
    public function contextualLinksViewAlter(&$element, $items) {
        if (isset($element['#links']['contextual-test-ajax'])) {
            $element['#attached']['library'][] = 'core/drupal.dialog.ajax';
        }
    }
    
    /**
     * Implements hook_page_attachments_alter().
     */
    public function pageAttachmentsAlter(array &$attachments) {
        $attachments['#attached']['library'][] = 'core/drupal.dialog.ajax';
    }

}