BlockContentTypeDeleteForm.php

<?php

namespace Drupal\block_content\Form;

use Drupal\Core\Entity\EntityDeleteForm;
use Drupal\Core\Form\FormStateInterface;

/**
 * Provides a confirmation form for deleting a block type entity.
 *
 * @internal
 */
class BlockContentTypeDeleteForm extends EntityDeleteForm {
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state) {
        $block_count = $this->entityTypeManager
            ->getStorage('block_content')
            ->getQuery()
            ->accessCheck(FALSE)
            ->condition('type', $this->entity
            ->id())
            ->count()
            ->execute();
        if ($block_count) {
            $caption = '<p>' . $this->formatPlural($block_count, '%label is used by 1 content block on your site. You can not remove this block type until you have removed all of the %label blocks.', '%label is used by @count content blocks on your site. You may not remove %label until you have removed all of the %label content blocks.', [
                '%label' => $this->entity
                    ->label(),
            ]) . '</p>';
            $form['description'] = [
                '#markup' => $caption,
            ];
            return $form;
        }
        else {
            return parent::buildForm($form, $form_state);
        }
    }

}