Fix ESLint import alias and preserve Formula placeholder for invalid currency

- Use relative './Log' / '@libs/Log' instead of '@src/libs/Log' to satisfy
  @dword-design/import-alias/prefer-alias rule for files inside src/libs.
- Extract isValidCurrencyCode helper from sanitizeCurrencyCode in
  CurrencyUtils.ts and export it for callers that need to gate behavior
  on currency validity rather than transparently fall back to USD.
- Use isValidCurrencyCode in Formula.formatAmount to keep the original
  semantic of returning an empty string (which surfaces the formula
  placeholder upstream) when the source or display currency is malformed,
  instead of silently formatting as USD. Restores the
  'invalid source currency - should return placeholder' Jest expectation
  in FormulaTest that previously relied on Intl.NumberFormat throwing.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: mountiny

src/libs/CurrencyUtils.ts

@@ -1,10 +1,10 @@
 import Onyx from 'react-native-onyx';
 import CONST from '@src/CONST';
 import IntlStore from '@src/languages/IntlStore';
-import Log from '@src/libs/Log';
 import type {OnyxValues} from '@src/ONYXKEYS';
 import ONYXKEYS from '@src/ONYXKEYS';
 import type {Locale} from '@src/types/onyx';
+import Log from './Log';
 import {format, formatToParts} from './NumberFormatUtils';
 
 let currencyList: OnyxValues[typeof ONYXKEYS.CURRENCY_LIST] = {};
@@ -21,12 +21,20 @@ Onyx.connect({
 });
 
 /**
- * Validates a currency code and returns it unchanged if it is a valid ISO 4217 code (exactly 3 uppercase ASCII letters).
+ * Returns true when the provided value is a syntactically valid ISO 4217 currency code
+ * (exactly 3 uppercase ASCII letters).
+ */
+function isValidCurrencyCode(currencyCode: string | undefined | null): currencyCode is string {
+    return typeof currencyCode === 'string' && /^[A-Z]{3}$/.test(currencyCode);
+}
+
+/**
+ * Validates a currency code and returns it unchanged if it is a valid ISO 4217 code.
  * Returns CONST.CURRENCY.USD and logs a warning when the code is malformed or missing, to prevent Intl.NumberFormat
  * from throwing a RangeError. See https://github.com/Expensify/App/issues/91113
  */
 function sanitizeCurrencyCode(currencyCode: string): string {
-    if (/^[A-Z]{3}$/.test(currencyCode)) {
+    if (isValidCurrencyCode(currencyCode)) {
         return currencyCode;
     }
     Log.warn('CurrencyUtils: invalid currency code, defaulting to USD', {currencyCode});
@@ -209,6 +217,7 @@ function convertToDisplayStringWithoutCurrency(amountInCents: number, currency:
 }
 
 export {
+    isValidCurrencyCode,
     sanitizeCurrencyCode,
     getCurrencyDecimals,
     getCurrencyUnit,

src/libs/Formula.ts

@@ -4,7 +4,7 @@ import type {ValueOf} from 'type-fest';
 import CONST from '@src/CONST';
 import type {PersonalDetails, Policy, PolicyReportField, Report, Transaction} from '@src/types/onyx';
 import {isEmptyObject} from '@src/types/utils/EmptyObject';
-import {convertToDisplayString, convertToDisplayStringWithoutCurrency} from './CurrencyUtils';
+import {convertToDisplayString, convertToDisplayStringWithoutCurrency, isValidCurrencyCode} from './CurrencyUtils';
 import formatDate from './FormulaDatetime';
 import getBase62ReportID from './getBase62ReportID';
 import Log from './Log';
@@ -580,10 +580,19 @@ function formatAmount(amount: number | undefined, currency: string | undefined,
                 return null;
             }
 
+            // Return empty string for an unrecognized display currency so the placeholder is preserved upstream.
+            if (!isValidCurrencyCode(trimmedDisplayCurrency)) {
+                return '';
+            }
+
             return convertToDisplayString(absoluteAmount, trimmedDisplayCurrency);
         }
 
         if (currency) {
+            // Return empty string for an unrecognized source currency so the placeholder is preserved upstream.
+            if (!isValidCurrencyCode(currency)) {
+                return '';
+            }
             return convertToDisplayString(absoluteAmount, currency, true);
         }
 

src/libs/NumberFormatUtils/index.ts

@@ -1,7 +1,7 @@
 import intlPolyfill from '@libs/IntlPolyfill';
+import Log from '@libs/Log';
 import memoize from '@libs/memoize';
 import CONST from '@src/CONST';
-import Log from '@src/libs/Log';
 import type Locale from '@src/types/onyx/Locale';
 
 // Polyfill the Intl API if locale data is not as expected