Orphan line items after combining carts

To reproduce:

1. Add an item A to your cart.
2. Log in
3. Log out
4. Add an item A to your cart.
5. Log in

This is because our call in \Drupal\commerce_combine_carts\CartUnifier::combineCarts to:

$this->cartManager->addOrderItem($main_cart, $item, $combine);

Seems to assume that the order item will get moved over to the $main_cart where in fact, if there's already a duplicate and $combine is TRUE then it's entirely possible that the quantity will be increased on an already existing order item with a different id.

So, we can look at the return value and if it's different, remove the order item from the $other_cart, patch inbound.

Here's a couple of patches, one that just has the test and another that has the fix too.

Oh, this doesn't need to be assigned to me any more.

That makes sense for the reproduction steps, and the approach to the fix looks sound.

I haven't had a chance to test this, so just to confirm, is the test-only patch sufficient to make the test fail without the fix? If so then this seems good to go to me.

The last submitted patch, 6: commerce_combine_carts-3195585-6-orphan-item-tests.patch, failed testing. View results →
- codesniffer_fixes.patch Interdiff of automated coding standards fixes only.

With these test results being good, I think this fix is probably ready to go!

Merged that then.

Automatically closed - issue fixed for 2 weeks with no activity.