Split Bill - Unequal split of the total amount entered on the BNP

[lanitochka17]

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Action Performed:

1. Launch New Expensify app
2. Tap on FAB button
3. Select Split Bill
4. Tap on the currency
5. Select MMK currency
6. Enter an amount in the big number pad page
7. Click on the Next button
8. Select a couple of attendees from the list
9. Tap the Next confirmation button

Expected Result:

In the final confirmation screen next to each attendee should be an equal split of the total amount entered on the BNP

Actual Result:

Split Bill is not shared equally when User select MMK currency

Workaround:

Unknown

Platforms:

Which of our officially supported platforms is this issue occurring on?

• [x] Android / native
• [x] Android / Chrome
• [x] iOS / native
• [x] iOS / Safari
• [x] MacOS / Chrome / Safari
• [x] MacOS / Desktop

Version Number: 1.3.63-0

Reproducible in staging?: Y

Reproducible in production?: Y

If this was caught during regression testing, add the test name, ID and link from TestRail:

Email or phone of affected tester (no customers):

Logs: https://stackoverflow.com/c/expensify/questions/4856

Notes/Photos/Videos: Any additional supporting documentation

https://github.com/Expensify/App/assets/78819774/f808b149-5b02-410c-baaf-75030c24fe7a

Expensify/Expensify Issue URL:

Issue reported by: Applause - Internal Team

Slack conversation:

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[melvin-bot[bot]]

Triggered auto assignment to @laurenreidexpensify (Bug), see https://stackoverflow.com/c/expensify/questions/14418 for more details.

[melvin-bot[bot]]

Bug0 Triage Checklist (Main S/O)

• [ ] This "bug" occurs on a supported platform (ensure Platforms in OP are ✅)
• [ ] This bug is not a duplicate report (check E/App issues and #expensify-bugs)
  • If it is, comment with a link to the original report, close the issue and add any novel details to the original issue instead
• [ ] This bug is reproducible using the reproduction steps in the OP. S/O
  • If the reproduction steps are clear and you're unable to reproduce the bug, check with the reporter and QA first, then close the issue.
  • If the reproduction steps aren't clear and you determine the correct steps, please update the OP.
• [ ] This issue is filled out as thoroughly and clearly as possible
  • Pay special attention to the title, results, platforms where the bug occurs, and if the bug happens on staging/production.
• [ ] I have reviewed and subscribed to the linked Slack conversation to ensure Slack/Github stay in sync

[alphaboss1104]

Proposal

Please re-state the problem that we are trying to solve in this issue.

Split Bill - Unequal split of the total amount entered on the BNP

What is the root cause of that problem?

If we are going to split the MMK 3 to 3 participants or split some money that currency's decimals is 0, currencyUnit is set as 1 and totalInCurrencySubunit is set as 3.

And Ideally amountPerPerson should be set as 0.75 but it is set as 1 because of Math.round().

https://github.com/Expensify/App/blob/1bdc5acc12f982b4f6e37bfadf9060ac3d2d3b3c/src/libs/IOUUtils.js#L15-L29

This is the first root cause.

And then minimumFractionDigits is the second root cause. In the code below if the currency isn't RSD, the minimumFractionDigits is set as undefined. And when minimumFractionDigits is undefined, the actual number of fraction digits used depends on the currency. So we couldn't get the correct value.

https://github.com/Expensify/App/blob/1bdc5acc12f982b4f6e37bfadf9060ac3d2d3b3c/src/libs/CurrencyUtils.js#L127C95-L119-L128

What changes do you think we should make in order to solve the problem?

We should remove the Math.round() in the code here.

      function calculateAmount(numberOfParticipants, total, currency, isDefaultUser = false) {
          const currencyUnit = Math.min(100, CurrencyUtils.getCurrencyUnit(currency));
-         const totalInCurrencySubunit = Math.round((total / 100) * currencyUnit);
+         const totalInCurrencySubunit = (total / 100) * currencyUnit;
          const totalParticipants = numberOfParticipants + 1;
-         const amountPerPerson = Math.round(totalInCurrencySubunit / totalParticipants);
+         const amountPerPerson = totalInCurrencySubunit / totalParticipants;
          let finalAmount = amountPerPerson;
          if (isDefaultUser) {
              const sumAmount = amountPerPerson * totalParticipants;
              const difference = totalInCurrencySubunit - sumAmount;
              finalAmount = totalInCurrencySubunit !== sumAmount ? amountPerPerson + difference : amountPerPerson;
          }
-         return Math.round((finalAmount * 100) / currencyUnit);
+         return (finalAmount * 100) / currencyUnit;
      }

And then also we should change the code here.

    return NumberFormatUtils.format(BaseLocaleListener.getPreferredLocale(), convertedAmount, {
        style: 'currency',
        currency,
-       minimumFractionDigits: currency === 'RSD' ? getCurrencyDecimals(currency) : undefined,
+       minimumFractionDigits: 2,
    });

What alternative solutions did you explore? (Optional)

None.

[hungvu193]

Dupe of https://github.com/Expensify/App/issues/14205. It was decided to close.

[laurenreidexpensify]

Thanks @hungvu193 am closing