Fix currency handling - always handle backend amounts as if they are in cents

src/libs/CurrencyUtils.js

@@ -28,7 +28,7 @@ Onyx.connect({
  */
 function getCurrencyDecimals(currency = CONST.CURRENCY.USD) {
     const decimals = lodashGet(currencyList, [currency, 'decimals']);
-    return _.isUndefined(decimals) ? 2 : Math.min(decimals, 2);
+    return _.isUndefined(decimals) ? 2 : decimals;
 }
 
 /**
@@ -73,54 +73,49 @@ function isCurrencySymbolLTR(currencyCode) {
 }
 
 /**
- * Takes an amount as a floating point number and converts it to an integer amount.
- * For example, given [25, USD], return 2500.
- * Given [25.50, USD] return 2550.
- * Given [2500, JPY], return 2500.
+ * Takes an amount as a floating point number and converts it to an integer equivalent to the amount in "cents".
+ * This is because the backend always stores amounts in "cents". The backend works in integer cents to avoid precision errors
+ * when doing math operations.
  *
- * @note we do not currently support any currencies with more than two decimal places. Sorry Tunisia :(
+ * @note we do not currently support any currencies with more than two decimal places. Decimal past the second place will be rounded. Sorry Tunisia :(
  *
- * @param {String} currency
  * @param {Number} amountAsFloat
  * @returns {Number}
  */
-function convertToSmallestUnit(currency, amountAsFloat) {
-    const currencyUnit = getCurrencyUnit(currency);
-    // We round off the number to resolve floating-point precision issues.
-    return Math.round(amountAsFloat * currencyUnit);
+function convertToBackendAmount(amountAsFloat) {
+    return Math.round(amountAsFloat * 100);
 }
 
 /**
- * Takes an amount as an integer and converts it to a floating point amount.
- * For example, give [25, USD], return 0.25
- * Given [2550, USD], return 25.50
- * Given [2500, JPY], return 2500
+ * Takes an amount in "cents" as an integer and converts it to a floating point amount used in the frontend.
  *
  * @note we do not support any currencies with more than two decimal places.
  *
- * @param {String} currency
  * @param {Number} amountAsInt
  * @returns {Number}
  */
-function convertToWholeUnit(currency, amountAsInt) {
-    const currencyUnit = getCurrencyUnit(currency);
-    return Math.trunc(amountAsInt) / currencyUnit;
+function convertToFrontendAmount(amountAsInt) {
+    return Math.trunc(amountAsInt) / 100.0;
 }
 
 /**
- * Given an amount in the smallest units of a currency, convert it to a string for display in the UI.
+ * Given an amount in the "cents", convert it to a string for display in the UI.
+ * The backend always handle things in "cents" (subunit equal to 1/100)
  *
- * @param {Number} amountInSmallestUnit – should be an integer. Anything after a decimal place will be dropped.
+ * @param {Number} amountInCents – should be an integer. Anything after a decimal place will be dropped.
  * @param {String} currency
  * @returns {String}
  */
-function convertToDisplayString(amountInSmallestUnit, currency = CONST.CURRENCY.USD) {
-    const currencyUnit = getCurrencyUnit(currency);
-    const convertedAmount = Math.trunc(amountInSmallestUnit) / currencyUnit;
+function convertToDisplayString(amountInCents, currency = CONST.CURRENCY.USD) {
+    const convertedAmount = convertToFrontendAmount(amountInCents);
     return NumberFormatUtils.format(BaseLocaleListener.getPreferredLocale(), convertedAmount, {
         style: 'currency',
         currency,
+
+        // We are forcindg the number of decimals because we overridden the default number of decimals in the backend for RSD
+        // See: https://github.com/Expensify/PHP-Libs/pull/834
+        minimumFractionDigits: currency === 'RSD' ? getCurrencyDecimals(currency) : undefined,
     });
 }
 
-export {getCurrencyDecimals, getCurrencyUnit, getLocalizedCurrencySymbol, isCurrencySymbolLTR, convertToSmallestUnit, convertToWholeUnit, convertToDisplayString};
+export {getCurrencyDecimals, getCurrencyUnit, getLocalizedCurrencySymbol, isCurrencySymbolLTR, convertToBackendAmount, convertToFrontendAmount, convertToDisplayString};

src/libs/ReportUtils.js

@@ -11,7 +11,6 @@ import * as Expensicons from '../components/Icon/Expensicons';
 import Navigation from './Navigation/Navigation';
 import ROUTES from '../ROUTES';
 import * as NumberUtils from './NumberUtils';
-import * as NumberFormatUtils from './NumberFormatUtils';
 import * as ReportActionsUtils from './ReportActionsUtils';
 import Permissions from './Permissions';
 import DateUtils from './DateUtils';
@@ -39,17 +38,6 @@ Onyx.connect({
     },
 });
 
-let preferredLocale = CONST.LOCALES.DEFAULT;
-Onyx.connect({
-    key: ONYXKEYS.NVP_PREFERRED_LOCALE,
-    callback: (val) => {
-        if (!val) {
-            return;
-        }
-        preferredLocale = val;
-    },
-});
-
 let allPersonalDetails;
 let currentUserPersonalDetails;
 Onyx.connect({
@@ -1724,8 +1712,7 @@ function buildOptimisticExpenseReport(chatReportID, policyID, payeeAccountID, to
  * @returns {Array}
  */
 function getIOUReportActionMessage(type, total, comment, currency, paymentType = '', isSettlingUp = false) {
-    const currencyUnit = CurrencyUtils.getCurrencyUnit(currency);
-    const amount = NumberFormatUtils.format(preferredLocale, Math.abs(total) / currencyUnit, {style: 'currency', currency});
+    const amount = CurrencyUtils.convertToDisplayString(total, currency);
     let paymentMethodMessage;
     switch (paymentType) {
         case CONST.IOU.PAYMENT_TYPE.ELSEWHERE:

src/pages/iou/steps/MoneyRequestAmountForm.js

@@ -62,7 +62,7 @@ function MoneyRequestAmountForm({amount, currency, isEditing, forwardedRef, onCu
 
     const textInput = useRef(null);
 
-    const selectedAmountAsString = amount ? CurrencyUtils.convertToWholeUnit(currency, amount).toString() : '';
+    const selectedAmountAsString = amount ? CurrencyUtils.convertToFrontendAmount(amount).toString() : '';
 
     const [currentAmount, setCurrentAmount] = useState(selectedAmountAsString);
     const [shouldUpdateSelection, setShouldUpdateSelection] = useState(true);
@@ -102,7 +102,7 @@ function MoneyRequestAmountForm({amount, currency, isEditing, forwardedRef, onCu
         if (!currencyCode || !amountInCurrencyUnits) {
             return;
         }
-        const amountAsStringForState = CurrencyUtils.convertToWholeUnit(currencyCode, amountInCurrencyUnits).toString();
+        const amountAsStringForState = CurrencyUtils.convertToFrontendAmount(amountInCurrencyUnits).toString();
         setCurrentAmount(amountAsStringForState);
         setSelection({
             start: amountAsStringForState.length,

src/pages/iou/steps/NewRequestAmountPage.js

@@ -147,7 +147,7 @@ function NewRequestAmountPage({route, iou, report, errors}) {
     };
 
     const navigateToNextPage = (currentAmount) => {
-        const amountInSmallestCurrencyUnits = CurrencyUtils.convertToSmallestUnit(currency, Number.parseFloat(currentAmount));
+        const amountInSmallestCurrencyUnits = CurrencyUtils.convertToBackendAmount(Number.parseFloat(currentAmount));
         IOU.setMoneyRequestAmount(amountInSmallestCurrencyUnits);
         IOU.setMoneyRequestCurrency(currency);
 

tests/unit/CurrencyUtilsTest.js

@@ -85,36 +85,36 @@ describe('CurrencyUtils', () => {
         });
     });
 
-    describe('convertToSmallestUnit', () => {
+    describe('convertToBackendAmount', () => {
         test.each([
-            [CONST.CURRENCY.USD, 25, 2500],
-            [CONST.CURRENCY.USD, 25.25, 2525],
-            [CONST.CURRENCY.USD, 25.5, 2550],
-            [CONST.CURRENCY.USD, 2500, 250000],
-            [CONST.CURRENCY.USD, 80.6, 8060],
-            [CONST.CURRENCY.USD, 80.9, 8090],
-            [CONST.CURRENCY.USD, 80.99, 8099],
-            ['JPY', 25, 25],
-            ['JPY', 25.25, 25],
-            ['JPY', 25.5, 26],
-            ['JPY', 2500, 2500],
-            ['JPY', 80.6, 81],
-            ['JPY', 80.9, 81],
-            ['JPY', 80.99, 81],
-        ])('Correctly converts %s to amount in smallest units', (currency, amount, expectedResult) => {
-            expect(CurrencyUtils.convertToSmallestUnit(currency, amount)).toBe(expectedResult);
+            [25, 2500],
+            [25.25, 2525],
+            [25.5, 2550],
+            [2500, 250000],
+            [80.6, 8060],
+            [80.9, 8090],
+            [80.99, 8099],
+            [25, 2500],
+            [25.25, 2525],
+            [25.5, 2550],
+            [2500, 250000],
+            [80.6, 8060],
+            [80.9, 8090],
+            [80.99, 8099],
+        ])('Correctly converts %s to amount in cents (subunit) handled in backend', (amount, expectedResult) => {
+            expect(CurrencyUtils.convertToBackendAmount(amount)).toBe(expectedResult);
         });
     });
 
-    describe('convertToWholeUnit', () => {
+    describe('convertToFrontendAmount', () => {
         test.each([
-            [CONST.CURRENCY.USD, 2500, 25],
-            [CONST.CURRENCY.USD, 2550, 25.5],
-            ['JPY', 25, 25],
-            ['JPY', 2500, 2500],
-            ['JPY', 25.5, 25],
-        ])('Correctly converts %s to amount in whole units', (currency, amount, expectedResult) => {
-            expect(CurrencyUtils.convertToWholeUnit(currency, amount)).toBe(expectedResult);
+            [2500, 25],
+            [2550, 25.5],
+            [25, 0.25],
+            [2500, 25],
+            [2500.5, 25], // The backend should never send a decimal .5 value
+        ])('Correctly converts %s to amount in units handled in frontend', (amount, expectedResult) => {
+            expect(CurrencyUtils.convertToFrontendAmount(amount)).toBe(expectedResult);
         });
     });
 
@@ -124,9 +124,13 @@ describe('CurrencyUtils', () => {
             [CONST.CURRENCY.USD, 2500, '$25.00'],
             [CONST.CURRENCY.USD, 150, '$1.50'],
             [CONST.CURRENCY.USD, 250000, '$2,500.00'],
-            ['JPY', 25, '¥25'],
-            ['JPY', 2500, '¥2,500'],
-            ['JPY', 25.5, '¥25'],
+            ['JPY', 2500, '¥25'],
+            ['JPY', 250000, '¥2,500'],
+            ['JPY', 2500.5, '¥25'],
+            ['RSD', 100, 'RSD\xa01.00'],
+            ['RSD', 145, 'RSD\xa01.45'],
+            ['BHD', 12345, 'BHD\xa0123.450'],
+            ['BHD', 1, 'BHD\xa00.010'],
         ])('Correctly displays %s', (currency, amount, expectedResult) => {
             expect(CurrencyUtils.convertToDisplayString(amount, currency)).toBe(expectedResult);
         });

tests/unit/currencyList.json

@@ -622,7 +622,6 @@
     "RSD": {
         "symbol": "РСД",
         "name": "Serbian Dinar",
-        "decimals": 0,
         "ISO4217": "941"
     },
     "RUB": {