Checkout: Whitespace in front of coupon code causes "Coupon code is not valid"

[AndrewPenry]

Preconditions

1. Magento 2.1.10 with Sample Data
2. PHP Version 7.0.22

Steps to reproduce

1. Open checkout page and complete up to Payment step
2. Fill in a coupon code with leading whitespace, like " H20"
3. Click "Apply Discount"

Expected result

1. The Discount should be applied

Actual result

1. "Coupon code is not valid"
2. In the logs: PUT /rest/default/V1/guest-carts/64610d8402c5f9e919929442220967ca/coupons/%20H20 HTTP/1.1

Note that whitespace after the coupon code is not being encoded in the PUT string, so the coupon works with trailing whitespace, just not with leading whitespace.

[magento-engcom-team]

@AndrewPenry, thank you for your report.
We've created internal ticket(s) MAGETWO-85582 to track progress on the issue.

[okorshenko]

Hi @AndrewPenry
The issue has been fixed and delivered in 2.2-develop branch. Will be available with upcoming patch release.