Fix: Incorrect bill splits for some currencies

src/components/IOUConfirmationList.js

@@ -153,10 +153,17 @@ class IOUConfirmationList extends Component {
     getParticipantsWithAmount(participants) {
         return OptionsListUtils.getIOUConfirmationOptionsFromParticipants(
             participants,
-            this.props.numberFormat(IOUUtils.calculateAmount(participants, this.props.iouAmount) / 100, {
-                style: 'currency',
-                currency: this.props.iou.selectedCurrencyCode,
-            }),
+            this.props.numberFormat(
+                IOUUtils.calculateAmount(
+                    participants,
+                    this.props.iouAmount,
+                    this.props.iou.selectedCurrencyCode,
+                ) / IOUUtils.getCurrencyUnits(this.props.iou.selectedCurrencyCode),
+                {
+                    style: 'currency',
+                    currency: this.props.iou.selectedCurrencyCode,
+                },
+            ),
         );
     }
 
@@ -187,10 +194,18 @@ class IOUConfirmationList extends Component {
 
             const formattedMyPersonalDetails = OptionsListUtils.getIOUConfirmationOptionsFromMyPersonalDetail(
                 this.props.currentUserPersonalDetails,
-                this.props.numberFormat(IOUUtils.calculateAmount(selectedParticipants, this.props.iouAmount, true) / 100, {
-                    style: 'currency',
-                    currency: this.props.iou.selectedCurrencyCode,
-                }),
+                this.props.numberFormat(
+                    IOUUtils.calculateAmount(
+                        selectedParticipants,
+                        this.props.iouAmount,
+                        this.props.iou.selectedCurrencyCode,
+                        true,
+                    ) / IOUUtils.getCurrencyUnits(this.props.iou.selectedCurrencyCode),
+                    {
+                        style: 'currency',
+                        currency: this.props.iou.selectedCurrencyCode,
+                    },
+                ),
             );
 
             sections.push({

src/libs/IOUUtils.js

@@ -1,31 +1,80 @@
 import _ from 'underscore';
+import Onyx from 'react-native-onyx';
+import lodashGet from 'lodash/get';
 import CONST from '../CONST';
+import ONYXKEYS from '../ONYXKEYS';
+
+let currencyList = {};
+Onyx.connect({
+    key: ONYXKEYS.CURRENCY_LIST,
+    callback: (val) => {
+        if (_.isEmpty(val)) {
+            return;
+        }
+
+        currencyList = val;
+    },
+});
+
+/**
+ * Returns the number of digits after the decimal separator for a specific currency.
+ * For currencies that have decimal places > 2, floor to 2 instead:
+ * https://github.com/Expensify/App/issues/15878#issuecomment-1496291464
+ *
+ * @param {String} currency - IOU currency
+ * @returns {Number}
+ */
+function getCurrencyDecimals(currency) {
+    const decimals = lodashGet(currencyList, [currency, 'decimals']);
+    return _.isUndefined(decimals) ? 0 : Math.min(decimals, 2);
+}
+
+/**
+ * Returns the currency's minor unit quantity
+ * e.g. Cent in USD
+ *
+ * @param {String} currency - IOU currency
+ * @returns {Number}
+ */
+function getCurrencyUnits(currency) {
+    return 10 ** getCurrencyDecimals(currency);
+}
 
 /**
  * Calculates the amount per user given a list of participants
  * @param {Array} participants - List of logins for the participants in the chat. It should not include the current user's login.
  * @param {Number} total - IOU total amount
+ * @param {String} currency - IOU currency
  * @param {Boolean} isDefaultUser - Whether we are calculating the amount for the current user
+ * @param {Boolean} shouldConvertTo2DigitsFormat - Whether to convert the amount to 2-digits format
  * @returns {Number}
  */
-function calculateAmount(participants, total, isDefaultUser = false) {
+function calculateAmount(participants, total, currency, isDefaultUser = false, shouldConvertTo2DigitsFormat = false) {
     // Convert to cents before working with iouAmount to avoid
     // javascript subtraction with decimal problem -- when dealing with decimals,
     // because they are encoded as IEEE 754 floating point numbers, some of the decimal
     // numbers cannot be represented with perfect accuracy.
-    // Cents is temporary and there must be support for other currencies in the future
-    const iouAmount = Math.round(parseFloat(total * 100));
+    // Currencies that do not have minor units (i.e. no decimal place) are also supported.
+    // https://github.com/Expensify/App/issues/15878
+    const currencyUnits = getCurrencyUnits(currency);
+    const iouAmount = Math.round(parseFloat(total * currencyUnits));
+
     const totalParticipants = participants.length + 1;
     const amountPerPerson = Math.round(iouAmount / totalParticipants);
 
-    if (!isDefaultUser) {
-        return amountPerPerson;
+    let finalAmount = amountPerPerson;
+
+    if (isDefaultUser) {
+        const sumAmount = amountPerPerson * totalParticipants;
+        const difference = iouAmount - sumAmount;
+        finalAmount = iouAmount !== sumAmount ? (amountPerPerson + difference) : amountPerPerson;
     }
 
-    const sumAmount = amountPerPerson * totalParticipants;
-    const difference = iouAmount - sumAmount;
+    if (shouldConvertTo2DigitsFormat) {
+        finalAmount = (finalAmount * 100) / currencyUnits;
+    }
 
-    return iouAmount !== sumAmount ? (amountPerPerson + difference) : amountPerPerson;
+    return finalAmount;
 }
 
 /**
@@ -139,4 +188,6 @@ export {
     updateIOUOwnerAndTotal,
     getIOUReportActions,
     isIOUReportPendingCurrencyConversion,
+    getCurrencyUnits,
+    getCurrencyDecimals,
 };

src/libs/actions/IOU.js

@@ -311,8 +311,8 @@ function createSplitsAndOnyxData(participants, currentUserLogin, amount, comment
     ];
 
     // Loop through participants creating individual chats, iouReports and reportActionIDs as needed
-    const splitAmount = IOUUtils.calculateAmount(participants, amount);
-    const splits = [{email: currentUserEmail, amount: IOUUtils.calculateAmount(participants, amount, true)}];
+    const splitAmount = IOUUtils.calculateAmount(participants, amount, currency, false, true);
+    const splits = [{email: currentUserEmail, amount: IOUUtils.calculateAmount(participants, amount, currency, true, true)}];
 
     const hasMultipleParticipants = participants.length > 1;
     _.each(participants, (participant) => {

tests/unit/IOUUtilsTest.js

@@ -132,3 +132,28 @@ describe('isIOUReportPendingCurrencyConversion', () => {
     });
 });
 
+describe('getCurrencyDecimals', () => {
+    test('Currency decimals smaller than or equal 2', () => {
+        expect(IOUUtils.getCurrencyDecimals('JPY')).toBe(0);
+        expect(IOUUtils.getCurrencyDecimals('USD')).toBe(2);
+    });
+
+    test('Currency decimals larger than 2 should return 2', () => {
+        // Actual: 3
+        expect(IOUUtils.getCurrencyDecimals('LYD')).toBe(2);
+
+        // Actual: 4
+        expect(IOUUtils.getCurrencyDecimals('UYW')).toBe(2);
+    });
+});
+
+describe('getCurrencyUnits', () => {
+    test('Currency with decimals smaller than or equal 2', () => {
+        expect(IOUUtils.getCurrencyUnits('JPY')).toBe(1);
+        expect(IOUUtils.getCurrencyUnits('USD')).toBe(100);
+    });
+
+    test('Currency with decimals larger than 2 should be floor to 2', () => {
+        expect(IOUUtils.getCurrencyUnits('LYD')).toBe(100);
+    });
+});