Graphql - Merge cart not working correctly when Backorder is enabled

[tushardatar7]

Preconditions and environment

• Magento: 2.4.7-p5
  -PHP 8.3
• Backorder configuration enabled (Allow Qty Below 0)
• Simple / virtual product with 0 qty and Backorder flag set as (Use config settings)

Steps to reproduce

Admin -

1. Enable Backorders (Allow Qty Below 0)
2. Set Qty for product as 0

Frontend / Graphql-

1. Login as customer (mutation generateCustomerToken)
2. Create / Get Customer cart (customerCart query)
3. Add product with 2 qty
4. logout
5. Create empty guest cart (mutation createEmptyCart)
6. Add same product with 3 qty in guest cart.
7. Merge Guest cart to customer cart (mutation MergeCarts)
8. Fetch cart details (cart query)

Expected result

Customer Cart should have product with 5 qty.

Actual result

Customer cart have product with only 2 qty (guest qty is not merged)

Additional information

1. Merge Cart mutation calls Magento\QuoteGraphQl\Model\Cart\MergeCarts\CartQuantityValidatorInterface::validateFinalCartQuantities
2. In this, products current stock validates with customer cart qty + guest cart qty.
3. it deletes product from guest cart if product stock condition is not satisfied

if ($stockCurrentQty < $guestCartItem->getQty() + $customerCartItem->getQty()) {
$this->cartItemRepository->deleteById($guestCart->getId(), $guestCartItem->getItemId());
$modified = true;
}

Release note

No response

Triage and priority

• Severity: S0 - Affects critical data or functionality and leaves users without workaround.
• Severity: S1 - Affects critical data or functionality and forces users to employ a workaround.
• Severity: S2 - Affects non-critical data or functionality and forces users to employ a workaround.
• Severity: S3 - Affects non-critical data or functionality and does not force users to employ a workaround.
• Severity: S4 - Affects aesthetics, professional look and feel, “quality” or “usability”.

[m2-assistant]

Hi @tushardatar7. Thank you for your report.
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[tushardatar7]

@magento I am working on this

[m2-assistant]

Hi @engcom-November. Thank you for working on this issue.
In order to make sure that issue has enough information and ready for development, please read and check the following instruction: 👇

• 1. Verify that issue has all the required information. (Preconditions, Steps to reproduce, Expected result, Actual result).
• 2. Verify that issue has a meaningful description and provides enough information to reproduce the issue.
• 3. Add Area: XXXXX label to the ticket, indicating the functional areas it may be related to.
• 4. Verify that the issue is reproducible on 2.4-develop branch
  Details

  - If the issue is reproducible on 2.4-develop branch, please, add the label Reproduced on 2.4.x.
  - If the issue is not reproducible, add your comment that issue is not reproducible and close the issue and stop verification process here!
• 5. Add label Issue: Confirmed once verification is complete.
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[tushardatar7]

@magento give me 2.4-develop instance

[tushardatar7]

@magento give me 2.4-develop instance

[tushardatar7]

@engcom-November Can you please confirm if you are able to reproduce issue.

[engcom-November]

Hello @tushardatar7 ,

Thank you for the report and your collaboration.

We attempted to reproduce the reported issue on our latest 2.4-develop instance and were able to successfully replicate it. Please find the attached screenshots for your reference.

Steps to Reproduce:

• Log in as a customer (mutation generateCustomerToken)
• Create or retrieve the customer cart (customerCart query)
• Add a product with quantity 2
• Log out
• Create an empty guest cart (mutation createEmptyCart)
• Add the same product with quantity 3 to the guest cart
• Merge the guest cart into the customer cart (mutation MergeCarts)
• Fetch the cart details (cart query)

We followed the provided preconditions, description, and reproduction steps, and were able to observe the issue as described.

Accordingly, we are marking this as "Issue: Confirmed."

Thank you once again!