Field notes from shipping a Shopify app

Where Shopify doesn't behave the way its documentation says.

These cost real time. None came from reading the docs. In one case the docs are just wrong: they call two cart fields the same field, and on a live cart those two fields came back $120 apart.

For developers

• Shopify cart price fields: what line_price and final_line_price actually mean Measured The deprecation note says one is an alias for the other. It isn’t. Which field reflects cart-level discounts, which reflects line-level, and which one you should actually gate on when you need to know a line is free.

For merchants

• How to add a free gift with purchase on Shopify Three ways to run it. The first needs no app at all, and for some stores it’s the right answer. Also the two failures that quietly break free-gift promotions, one of which ends with your shopper paying for the gift.