Incorrect Backorder Quantity Handling When Adding Same Product to Cart With Different Custom Options

[rutvik-monpara]

Fixed Issues

1. Fixes Incorrect Backorder Quantity Handling When Adding Same Product to Cart With Different Custom Options #3446: Incorrect Backorder Quantity Handling When Adding Same Product to Cart With Different Custom Options

Manual testing scenarios

1. Create a simple product with custom options.
2. Set product stock quantity to 10.

3. Enable backorders: Catalog > Products > Advanced Inventory > Backorders > Allow Qty Below 0 and Notify Customer
4. On frontend, add the same product to the cart twice, each with a different custom option. For each cart item, set quantity to 20.

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds are green)

[engcom-Hotel]

@magento run all tests

[engcom-Hotel]

Hello @rutvik-monpara,

Thank you for your report and collaboration!

Please refer to the below review comments and also please cover the PR changes with some automated tests.

Thank you

[engcom-Hotel]

The PR introduces instance-level state in service classes, according to the Magento 2 coding guidelines "Services SHOULD be stateless".

[engcom-Hotel]

I guess the subtraction logic produces WRONG results.
It subtracts the previously stored backorder qty, resulting in 0 for the second item instead of showing the correct cumulative backorder.

for e.g.

Call	Scenario	Expected	Actual with this code
1st	Item A, qty=20, stock=10	backorder=10	backorder=10 ✓ (stored: 10)
2nd	Item B, qty=20, stock=10	backorder=20 (cumulative)	backorder=0 (10-10=0) ✗