Change in number format to fix loss of precision for very big values

Author: jpuri

ui/pages/confirmations/components/simulation-details/formatAmount.test.ts

@@ -37,14 +37,10 @@ describe('formatAmount', () => {
     [47361034.006, '47,361,034'],
     ['12130982923409.5', '12,130,982,923,410'],
     ['1213098292340944.5', '1,213,098,292,340,945'],
-    // Precision is lost after the value is greator than Number.MAX_SAFE_INTEGER. The digits after
-    // the 15th digit become 0's.
-    // TODO fix the precision
-    /** @see {@link https://github.com/MetaMask/metamask-extension/issues/25755} */
-    ['30001231231212312138768', '30,001,231,231,212,312,000,000'],
+    ['30001231231212312138768', '30,001,231,231,212,312,138,768'],
     [
-      '115792089237316195423570985008687907853269984665640564039457584007913129639935',
-      '115,792,089,237,316,200,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000',
+      '1157920892373161954235709850086879078532699846656405640394575.84007913129639935',
+      '1,157,920,892,373,161,954,235,709,850,086,879,078,532,699,846,656,405,640,394,576',
     ],
   ])(
     'formats amount greater than or equal to 1 with appropriate decimal precision (%s => %s)',

ui/pages/confirmations/components/simulation-details/formatAmount.ts

@@ -80,6 +80,12 @@ export function formatAmount(locale: string, amount: BigNumber): string {
     MAX_SIGNIFICANT_DECIMAL_PLACES - digitsLeftOfDecimal + 1,
   );
 
+  if (maximumFractionDigits === 0) {
+    // No decimals to display – we can use BigInt to localize without loss of precision.
+    return BigInt(amount.toFixed(0)).toLocaleString(locale);
+  }
+
+  // At most 4 (MAX_SIGNIFICANT_DECIMAL_PLACES + 1) significant digits – Use Intl.NumberFormat to localize
   return new Intl.NumberFormat(locale, {
     maximumFractionDigits,
   } as Intl.NumberFormatOptions).format(amount.toNumber());