[CP Staging] Fix tax rate being updated when currency is updated in offline mode

src/libs/ReportUtils.ts

@@ -2982,7 +2982,8 @@ function getModifiedExpenseOriginalMessage(
 
     // The amount is always a combination of the currency and the number value so when one changes we need to store both
     // to match how we handle the modified expense action in oldDot
-    if ('amount' in transactionChanges || 'currency' in transactionChanges) {
+    const didAmountOrCurrencyChange = 'amount' in transactionChanges || 'currency' in transactionChanges;
+    if (didAmountOrCurrencyChange) {
         originalMessage.oldAmount = TransactionUtils.getAmount(oldTransaction, isFromExpenseReport);
         originalMessage.amount = transactionChanges?.amount ?? transactionChanges.oldAmount;
         originalMessage.oldCurrency = TransactionUtils.getCurrency(oldTransaction);
@@ -2999,19 +3000,22 @@ function getModifiedExpenseOriginalMessage(
         originalMessage.tag = transactionChanges?.tag;
     }
 
+    // We only want to display a tax rate update system message when tax rate is updated by user.
+    // Tax rate can change as a result of currency update. In such cases, we want to skip displaying a system message, as discussed.
+    const didTaxCodeChange = 'taxCode' in transactionChanges;
+    if (didTaxCodeChange && !didAmountOrCurrencyChange) {
+        originalMessage.oldTaxRate = policy?.taxRates?.taxes[TransactionUtils.getTaxCode(oldTransaction)]?.value;
+        originalMessage.taxRate = transactionChanges?.taxCode && policy?.taxRates?.taxes[transactionChanges?.taxCode].value;
+    }
+
     // We only want to display a tax amount update system message when tax amount is updated by user.
     // Tax amount can change as a result of amount, currency or tax rate update. In such cases, we want to skip displaying a system message, as discussed.
-    if ('taxAmount' in transactionChanges && !('amount' in transactionChanges || 'currency' in transactionChanges || 'taxCode' in transactionChanges)) {
+    if ('taxAmount' in transactionChanges && !(didAmountOrCurrencyChange || didTaxCodeChange)) {
         originalMessage.oldTaxAmount = TransactionUtils.getTaxAmount(oldTransaction, isFromExpenseReport);
         originalMessage.taxAmount = transactionChanges?.taxAmount;
         originalMessage.currency = TransactionUtils.getCurrency(oldTransaction);
     }
 
-    if ('taxCode' in transactionChanges) {
-        originalMessage.oldTaxRate = policy?.taxRates?.taxes[TransactionUtils.getTaxCode(oldTransaction)]?.value;
-        originalMessage.taxRate = transactionChanges?.taxCode && policy?.taxRates?.taxes[transactionChanges?.taxCode].value;
-    }
-
     if ('billable' in transactionChanges) {
         const oldBillable = TransactionUtils.getBillable(oldTransaction);
         originalMessage.oldBillable = oldBillable ? Localize.translateLocal('common.billable').toLowerCase() : Localize.translateLocal('common.nonBillable').toLowerCase();

src/libs/actions/IOU.ts

@@ -5092,6 +5092,7 @@ type UpdateMoneyRequestAmountAndCurrencyParams = {
     policy?: OnyxEntry<OnyxTypes.Policy>;
     policyTagList?: OnyxEntry<OnyxTypes.PolicyTagList>;
     policyCategories?: OnyxEntry<OnyxTypes.PolicyCategories>;
+    taxCode: string;
 };
 
 /** Updates the amount and currency fields of an expense */
@@ -5104,10 +5105,12 @@ function updateMoneyRequestAmountAndCurrency({
     policy,
     policyTagList,
     policyCategories,
+    taxCode,
 }: UpdateMoneyRequestAmountAndCurrencyParams) {
     const transactionChanges = {
         amount,
         currency,
+        taxCode,
         taxAmount,
     };
     const transactionThreadReport = allReports?.[`${ONYXKEYS.COLLECTION.REPORT}${transactionThreadReportID}`] ?? null;

src/pages/iou/request/step/IOURequestStepAmount.tsx

@@ -56,16 +56,6 @@ type IOURequestStepAmountProps = IOURequestStepAmountOnyxProps &
         transaction: OnyxEntry<OnyxTypes.Transaction>;
     };
 
-function getTaxAmount(transaction: OnyxEntry<OnyxTypes.Transaction>, policy: OnyxEntry<OnyxTypes.Policy>, newAmount: number) {
-    if (!transaction?.amount) {
-        return 0;
-    }
-    const transactionTaxCode = transaction?.taxCode ?? '';
-    const defaultTaxCode = TransactionUtils.getDefaultTaxCode(policy, transaction) ?? '';
-    const taxPercentage = TransactionUtils.getTaxValue(policy, transaction, transactionTaxCode ?? defaultTaxCode) ?? '';
-    return CurrencyUtils.convertToBackendAmount(TransactionUtils.calculateTaxAmount(taxPercentage, newAmount));
-}
-
 function IOURequestStepAmount({
     report,
     route: {
@@ -279,7 +269,8 @@ function IOURequestStepAmount({
         }
 
         // If the value hasn't changed, don't request to save changes on the server and just close the modal
-        if (newAmount === TransactionUtils.getAmount(transaction) && currency === TransactionUtils.getCurrency(transaction)) {
+        const transactionCurrency = TransactionUtils.getCurrency(transaction);
+        if (newAmount === TransactionUtils.getAmount(transaction) && currency === transactionCurrency) {
             Navigation.dismissModal();
             return;
         }
@@ -290,9 +281,14 @@ function IOURequestStepAmount({
             return;
         }
 
-        const taxAmount = getTaxAmount(transaction, policy, newAmount);
+        // If currency has changed, then we get the default tax rate based on currency, otherwise we use the current tax rate selected in transaction, if we have it.
+        const transactionTaxCode = transaction?.taxCode ?? '';
+        const defaultTaxCode = TransactionUtils.getDefaultTaxCode(policy, transaction, currency) ?? '';
+        const taxCode = (currency !== transactionCurrency ? defaultTaxCode : transactionTaxCode) ?? defaultTaxCode;
+        const taxPercentage = TransactionUtils.getTaxValue(policy, transaction, taxCode) ?? '';
+        const taxAmount = CurrencyUtils.convertToBackendAmount(TransactionUtils.calculateTaxAmount(taxPercentage, newAmount));
 
-        IOU.updateMoneyRequestAmountAndCurrency({transactionID, transactionThreadReportID: reportID, currency, amount: newAmount, taxAmount});
+        IOU.updateMoneyRequestAmountAndCurrency({transactionID, transactionThreadReportID: reportID, currency, amount: newAmount, taxAmount, policy, taxCode});
         Navigation.dismissModal();
     };