Is there a way to enforce a specific number of products in a subscription?
I understand that a customer creates a subscription contract by adding products containing selling plans to their cart using the Cart API: https://shopify.dev/docs/api/ajax/reference/cart#add-a-selling-plan
Following on from this answer: https://community.shopify.com/c/subscriptions-apis/can-you-subscribe-to-multiple-products-in-a-subsc...
A cart containing multiple products with the same selling plan allocation in each product, they will be merged into the same subscription contract.
But, is there a way to require a specific number of products before a subscription can be created?
For example, if they are subscribing to a build your own 6 pack. Where they are required to choose 6 bottles before they can checkout.
I can enforce this prior to adding to the cart by making my own UI making the 6-pack configurable using a theme extension. But once they're in the cart and go to the checkout, there is no way to prevent the user from removing one of these products from their cart.
That's an interesting use case. There's nothing specific to subscriptions that supports this, but you might check out bundles. I haven't worked with bundles myself, so I can't promise anything, but I think they're worth a look. I hope this helps.
I have looked at this, but unfortunately selling plans aren't supported.
I also thought I could do this with a cart transformation app extension. But again, Selling Plans aren't supported.