The Order resource now validates the quantity of line items
API
Effective October 25, 2018
We're adding validation for line item quantities, which prevents the creation of line items with a quantity of 0. This means that orders created via the Order resource must have a line item quantity greater than or equal to 1.
If an app attempts to create a line item with a quantity of 0, then the Order resource returns a status of 422 with the error message Quantity must be greater than or equal to 1.
We're making this change to ensure consistent behaviour across the platform, since line items with a quantity of 0 can't be fulfilled within Shopify.
To learn more, see Order.