Hi,
we are currently developing an app using the merge cart transform. We have the app approved and are now working on making it work with as many themes as possible. While doing that, we came across an inconsistency in the Shopify Cart, which makes it impossible to use merged bundles in a lot of themes.
When adding two merged bundles into the cart, they share the same line item "id" value even if they have completely different bundle components. The cart handles them as two different line items but with the same id which should normally be unique to every line item as per the docs.
https://shopify.dev/docs/api/ajax/reference/cart#post-locale-cart-change-js
Many themes use this id to make quantity updates or changes in their carts which leads to both of the bundles beeing deleted/changed instead of only the one that is required.
With access to the theme, of course one could just use the "line" instead of the "id" but as app developer we don't have access to the theme in a way that would allow these changes.
I think this is probably not an intended behaviour and hope this gets to the right team here. If you need any additional information, screenrecording etc. I'm happy to help.
