Checkout with custom CarrierService only shows the first Subscription shipping rate option?

[Tristan3dt]

Hi,

I've built a custom CarrierService to return shipping rates.  I've got this working on the whole, but running into behaviour that I can't find documented, and an issue with subscription shipping rates.

First off, it seems that if there is a Subscription product in the cart then Shopify makes two requests to the CarrierService -- one containing one-off products AND subscription products, and one containing subscription products only.  At first this didn't make sense to me, but now I think I understand that the initial shipping cost for the subscription products is 'bundled' into the one-off products, and the second request is used for showing shipping cost for the renewal of the subscription.  If a cart ONLY contains subscription products, my CarrierService still seems to receive two identical requests from Shopify.  I can't find any documentation mentioning any of this behaviour though, can anyone point me in the right direction?

Secondly, and most confusingly: my CarrierRate is correctly returning two rates for each of these requests -- a tracked and an untracked option for each.  However, for the Subscription shipping part, the Shopify cart displays the first of these returned rates.

i.e., my CarrierService is returning:-

{"rates":[{"service_name":"Untracked subscription (4 untracked shipments of 1 copies)  (3-5 working days)","service_code":"UNTRACKED","total_price":500,"description":"Untracked subscription (4 untracked shipments of 1 copies)  (3-5 working days)","currency":"GBP"},{"service_name":"Tracked shipping (Tracked Yodel) (with 4 tracked magazine shipments)","service_code":"TRACKED","total_price":1886,"description":"Tracked shipping","currency":"GBP"}]}

But this is what is displayed on the cart page:

 - so only the first shipping rate is being displayed, with no option for customer to choose the second (in this case, tracked shipping for subscription renewals).

Again, I can't find any documentation describing this behaviour.  Is there a way to provide multiple options for subscription shipping?  Am I doing something wrong? 

Thanks,

[rexb]

I'm having an issue with this too. It would be perfect if someone from Shopify could give us more information about this