Incorrect discount amount when applying multiple 'Fixed amount discount for whole cart' rules

[nghia-34th]

Preconditions and environment

• Magento version: 2.4.7 and above

Steps to reproduce

1. Create at least three cart rules with the 'Fixed amount discount for whole cart' action.
2. Add product to cart.
3. Make sure the cart condition matches the three rules created in step 1.

Expected result

The Discount amount in the cart summary section should be correct.

Actual result

Incorrect Discount amount shown.

Additional information

Rule 1:

Rule 2:

Rule 3:

Expected discount amount should be 15,00 US$. The actual amount shown is 15,30 US$.

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 @nghia-34th. Thank you for your report.
To speed up processing of this issue, make sure that the issue is reproducible on the vanilla Magento instance following Steps to reproduce.

• For more details, review the Magento Contributor Assistant documentation.
• Add a comment to assign the issue: @magento I am working on this
• To learn more about issue processing workflow, refer to the Code Contributions.

---

Join Magento Community Engineering Slack and ask your questions in #github channel.
⚠️ According to the Magento Contribution requirements, all issues must go through the Community Contributions Triage process. Community Contributions Triage is a public meeting.
🕙 You can find the schedule on the Magento Community Calendar page.
📞 The triage of issues happens in the queue order. If you want to speed up the delivery of your contribution, join the Community Contributions Triage session to discuss the appropriate ticket.

[nghia-34th]

The issue is due to this class Magento\SalesRule\Model\Quote\Discount, line 209. $totalDiscount should be the sum of each rule's base discount applied to the current item.
Adding the item's base discount amount would re-add all the base discount amounts of previous rules to $totalDiscount, leading to incorrect discount amount calculation.

[m2-assistant]

Hi @engcom-Bravo. 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.
• 6. Make sure that automatic system confirms that report has been added to the backlog.

[engcom-Bravo]

Hi @nghia-34th,

Thanks for your reporting and collaboration.

We have tried to reproduce the issue in Latest 2.4-develop instance and the issue is not reproducible.Kindly refer the screenshots.

The Discount amount in the cart summary section was correctly applied.

Kindly recheck the issue in Latest 2.4-develop instance and elaborate the steps to reproduce if the issue is still reproducible.

Thanks.

[nghia-34th]

@magento give me 2.4-develop instance

[nghia-34th]

@engcom-Bravo I'm unable to request a 2.4-develop instance on this issue, do you have any advice?
This is reproducible on a fresh 2.4.7 installation btw.

[engcom-Bravo]

Hi @nghia-34th,

Thanks for your Update.

The Magento 2.4-develop instance service(MDS) has been decommissioned and since the issue is not reproducible in Latest 2.4-develop instance it might be possible the issue has been addressed and fixed in Latest 2.4-develop branch.Hence we are closing this issue.

Thanks.

[nghia-34th]

@engcom-Bravo Hold on now, you can't just make an assumption and immediately close the issue like that.
I've checked the code in 2.4-develop. Sure, it might resolve the example scenario that I've given above. But not all scenarios. Let's try again with multiple items in cart.

Step 1: Add more than one item to cart.
Step 2: Update one or more of the "Fixed amount discount for whole cart" rules configured above so that it should only apply to some specific items in cart but not all.

Step 3: Back to the cart page and reload

[engcom-Bravo]

Hi @nghia-34th,

Thanks for your update.

We are reopening this issue as per this comment #39536 (comment)

Thanks.

[engcom-Bravo]

Hi @nghia-34th,

Thanks for your update.

We have tried to reproduce the issue in Latest 2.4-develop instance and we are not able to reproduce the issue.Kindly refer the screenshots.

The Discount amount in the cart summary section was correctly applied.

Kindly recheck the issue in Latest 2.4-develop instance and elaborate the steps to reproduce if the issue is still reproducible.

Thanks.

[nghia-34th]

@engcom-Bravo I can see that you're adding two simple products, which both will match the condition of the rule "Test12". Please refer to the second step:

Update one or more of the "Fixed amount discount for whole cart" rules configured above so that it should only apply to some specific items in cart but not all.

English isn't my first language, so I might be wrong/missing context in this step. Maybe explaining it with an example would help you understand, it should look like this:

          |   ITEM A     |    ITEM B
RULE 1:   |   applied    |    applied
RULE 2:   |   applied    |    not applied
RULE 3:   |   applied    |    applied

In the above table, the RULE 2 condition is configured so that it only applies to one item, not all. And this is the scenario where it would trigger the error.

[engcom-Bravo]

Hi @nghia-34th,

Thanks for your update.

We have tried to reproduce the issue in Latest 2.4-develop instance and we are not able to reproduce the issue.Kindly refer the screenshots.

We have added one simple product and configurable product and the rule TEST12 only matches with the product Simple.The Discount amount in the cart summary section was correctly applied.

Kindly recheck the issue in Latest 2.4-develop instance and elaborate the steps to reproduce if the issue is still reproducible.

Thanks.

[nghia-34th]

Okay, you can close it then.

[engcom-Bravo]

Hi @nghia-34th,

Thanks for your Update.

We are closing this issue Please feel free to reopen the issue if the issue still persists.

Thanks.