Allow deleting a bundle item which has already been ordered

[lruozzi9]

Problem

ProductBundle removes its items with orphan-removal="true", so removing a product from a bundle in the admin issues a DELETE on bitbag_product_bundle_item.

But ProductBundleOrderItem references that same row through a join column mapped nullable="false" with no on-delete behaviour. As soon as a bundle item has been ordered at least once, deleting it fails:

An exception occurred while executing a query: SQLSTATE[23000]: Integrity constraint violation: 1451
Cannot delete or update a parent row: a foreign key constraint fails
(`bitbag_product_bundle_order_item`, CONSTRAINT `FK_A615CDA9B7FE950B`
 FOREIGN KEY (`product_bundle_item_id`) REFERENCES `bitbag_product_bundle_item` (`id`))

Stack trace ends in ResourceUpdateHandler->handle() → UnitOfWork->executeDeletions(), i.e. the plain admin product update.

This is not an edge case: any product ever sold inside a bundle becomes impossible to remove from that bundle.

Fix

-<join-column name="product_bundle_item_id" referenced-column-name="id" nullable="false"/>
+<join-column name="product_bundle_item_id" referenced-column-name="id" nullable="true" on-delete="SET NULL"/>

Why this is safe

• ProductBundleOrderItem::getProductBundleItem() is never read. ProductBundleOrderItemFactory::createFromProductBundleItem() writes it, and already copies the two values that matter onto the order item itself:

  $productBundleOrderItem->setProductBundleItem($bundleItem);
  $productBundleOrderItem->setProductVariant($bundleItem->getProductVariant()); // copied
  $productBundleOrderItem->setQuantity($bundleItem->getQuantity());             // copied

  So the order row is already self-sufficient; the pointer is redundant.

• Both ProductBundleOrderItemInterface::getProductBundleItem() and setProductBundleItem() are already typed nullable — only the mapping disagreed.

• config/serialization/ProductBundleOrderItem.xml exposes only id, productVariant and quantity; productBundleItem is in no serialization group, so API responses are unaffected.

• templates/Admin/Order/Show/_productBundleOrderItems.html.twig renders item.productVariant / item.quantity only.

• It mirrors the sibling order_item_id join column in the same file, which already declares on-delete="CASCADE".

Order history is preserved: the ordered variant and quantity stay on the row, only the link to the now-deleted bundle line is cleared.

Verification

Applied in a Sylius 2 project and tested against real data (~1600 bitbag_product_bundle_order_item rows):

• Deleting a bundle item referenced by 128 order rows now succeeds; those rows keep product_variant_id and quantity, with product_bundle_item_id set to NULL.
• doctrine:schema:update --dump-sql is clean afterwards.
• Removing a product from a bundle in the admin no longer raises the constraint violation.

Note for applications

The plugin ships no migrations, so consuming applications need one:

ALTER TABLE bitbag_product_bundle_order_item DROP FOREIGN KEY FK_A615CDA9B7FE950B;
ALTER TABLE bitbag_product_bundle_order_item CHANGE product_bundle_item_id product_bundle_item_id INT DEFAULT NULL;
ALTER TABLE bitbag_product_bundle_order_item ADD CONSTRAINT FK_A615CDA9B7FE950B FOREIGN KEY (product_bundle_item_id) REFERENCES bitbag_product_bundle_item (id) ON DELETE SET NULL;