D9: UntrustedCallbackException

Same issue as in comment #9.

$product_id is empty on Manage layout page of a product type (admin/commerce/config/product-types/default/edit/display/full)

Adding a check if $product_id is empty resolves the issue

public function ajaxAddToCartForm($product_id, $view_mode, $combine) {
    /** @var \Drupal\commerce_order\OrderItemStorageInterface $order_item_storage */
    $order_item_storage = $this->entityTypeManager->getStorage('commerce_order_item');

    if (empty($product_id)) {
      return [];
    }
    /** @var \Drupal\commerce_product\Entity\ProductInterface $product */
    $product = $this->entityTypeManager->getStorage('commerce_product')->load($product_id);
    $default_variation = $product->getDefaultVariation();
    if (!$default_variation) {
      return [];
    }

    $order_item = $order_item_storage->createFromPurchasableEntity($default_variation);
    /** @var \Drupal\commerce_cart\Form\AddToCartFormInterface $form_object */
    $form_object = $this->entityTypeManager->getFormObject('commerce_order_item', 'dc_ajax_add_cart');
    $form_object->setEntity($order_item);
    // The default form ID is based on the variation ID, but in this case the
    // product ID is more reliable (the default variation might change between
    // requests due to an availability change, for example).
    $form_object->setFormId($form_object->getBaseFormId() . '_commerce_product_' . $product_id);
    $form_state = (new FormState())->setFormState([
      'product' => $product,
      'view_mode' => $view_mode,
      'settings' => [
        'combine' => $combine,
      ],
    ]);

    return $this->formBuilder->buildForm($form_object, $form_state);
  }

Thanks for this info, is a patch or update available that fixes #12 also?

I am sorry to change status, but in order for this to work, I believe the adjustments in #12 would be necessary in order to avoid the errors reported?

Updated patch with comments in #12

I think this has been incorporated into the MR at 📌 Drupal 10 update Needs review

Might be a duplicate a this point

I suggest merging the MR in 📌 Drupal 10 update Needs review as it incorporates this issues' changes as well as the D10 compatibility changes from 📌 Drupal 10 update Needs review .