All Submissions:

• Does your code follow the WooCommerce Sniffs variant of WordPress coding standards?
• Have you written new tests for your changes, as applicable?
• Have you successfully run tests with your changes locally?
• Will this change require new documentation or changes to existing documentation?

Changes proposed in this Pull Request:

Modifies the configuration of API line items to account for partial quantities, these can be allowed by plugins such as Decimal Product Quantity for WooCommerce.

Closes https://linear.app/a8c/issue/SQUARE-156/a-critical-error-is-thrown-when-processing-orders-with-product
Closes #410

Steps to test the changes in this Pull Request:

1. Install Decimal Product Quantity for WooCommerce
2. Set up the site to use shortcode cart and checkout (required by plugin)
3. Create a $2 simple product with the quantity options:
   • Minimum: 0.5
   • Default set: 0.5
   • Step change +/-: 0.5
   • Price unit label: Price per half (or anything really)
4. Create a free shipping option
5. Purchase the product using the free shipping option
6. Ensure the purchase succeeds and does not trigger a fatal error

Noe: the fatal error happens in an ajax request so there's no white-screen-of-death on the front end of the site, the purchase fails with a generic error message.

Changelog entry

Fix - Fatal error when using partial product quantities via a plugin.