Restricts product attachment selection to the current post in the media library.php

<?php

/**
 * Restricts product attachment selection to the current post in the media library
 *
 * This function modifies the attachment query arguments to only show attachments
 * associated with the current product being edited.
 *
 * @param  array $query The current attachment query arguments.
 * @return array       The modified attachment query arguments.
 */
function restrict_product_attachment_to_current_post($query) {

  // 1. Validate user permissions (unchanged)
  if (!current_user_can('upload_files')) {
    wp_send_json_error();
  }

  // 2. Ensure a valid post ID is provided (unchanged)
  if (!isset($_REQUEST['post_id'])) {
    wp_send_json_error();
  }

  // 3. Retrieve the post object (unchanged)
  $post = get_post((int)$_REQUEST['post_id']);
  if (!$post instanceof \WP_Post) {
    return $query;
  }

  // 4. Restrict to WooCommerce product posts and their variations
  if ($post->post_type !== 'product' && $post->post_type !== 'product_variation') {
    return $query;
  }

  // 5. Filter by post parent (product) or post ID (variation)
  $query['post_parent'] = ($post->post_type === 'product') ? $post->ID : $post->post_parent;

  return $query;
}

add_filter('ajax_query_attachments_args', 'restrict_product_attachment_to_current_post');