applyCartLinesChange rounding off decimal places in CheckoutExtensions UI

Shopify Apps

Topic summary

A developer is building a donation checkout extension UI and encountering an issue with decimal handling in the applyCartLinesChange function.

The Problem:

  • When entering a custom donation amount of 1.5, the system automatically rounds it down to 1
  • The developer questions whether the cart transform function supports decimal places

Current Status:

  • The extension is otherwise functioning properly
  • Documentation doesn’t clearly indicate decimal support
  • A screenshot shows the rounding behavior in action
  • No responses or solutions have been provided yet
Summarized with AI on October 29. AI used: claude-sonnet-4-5-20250929.
1

Hello,

I’m currently creating a donation checkout extensions ui. It’s properly working but when I enter a custom amount of 1.5 it automatically rounds it off to 1. Does the cart transform function accept decimal places? I can’t see it in the docs.

Screenshot 2025-04-28 at 1.39.43 PM.png
Screenshot 2025-04-28 at 1.39.43 PM.png2322×1212 184 KB

Thank you!