SettingsTrayFormAnnotationNoneBlock.php

<?php

namespace Drupal\settings_tray_test\Plugin\Block;

use Drupal\Core\Block\BlockBase;

/**
 * Block that does nothing explicit for Settings Tray.
 *
 * @Block(
 *   id = "settings_tray_test_none",
 *   admin_label = "Settings Tray test block: forms[settings_tray] is not specified",
 * )
 */
class SettingsTrayFormAnnotationNoneBlock extends BlockBase {
    
    /**
     * {@inheritdoc}
     */
    public function build() {
        return [
            '#markup' => '<span>none</span>',
        ];
    }

}