I think it was a momentary mistake. Do you have such a mistake?
Topic summary
Cart scripts fail to stack with Shopify Functions discount codes, while native Shopify discount codes do stack with scripts. With a Functions-generated discount, the function discount is applied and script-based discounts are not, contrary to expectations.
Troubleshooting tried: changing “combination” settings (on/off) had no effect; creating a new empty script did not resolve it. Suggestions included adding nil checks and recreating the script, but the issue persisted.
Error observed: when a Functions discount runs, even the simplest cart script errors with “can’t convert nil into Decimal” on a single line: Output.cart = Input.cart. A screenshot was shared to show the error. Code snippet and error are central to understanding.
Conflicting reports: some participants state Scripts (Ruby-based) and Functions discounts (Shopify Functions) can work together, implying the problem may be environment-specific or a transient issue.
Recent update: a Shopify Partners Slack thread suggests this is a known issue (link provided). Another participant requested the debug URL for further analysis.
Status: unresolved/ongoing. Awaiting more debugging details or confirmation of a platform fix.