From 7596548e9b836a5d12e966bf296a4dbba044b78f Mon Sep 17 00:00:00 2001
From: Xia Chao <236466140+bun-unsafe@users.noreply.github.com>
Date: Tue, 25 Aug 2026 15:50:22 +0800
Subject: [PATCH] fix(common): use locale NaN symbol in number formatting

Non-finite values all used NumberSymbol.Infinity, so formatNumber(NaN)
rendered as infinity. Locale data already defines NumberSymbol.NaN.
---
 packages/common/src/i18n/format_number.ts       |  6 +++++-
 packages/common/test/i18n/format_number_spec.ts | 10 ++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/packages/common/src/i18n/format_number.ts b/packages/common/src/i18n/format_number.ts
index 6c7aa111805..7ef0f8154cb 100644
--- a/packages/common/src/i18n/format_number.ts
+++ b/packages/common/src/i18n/format_number.ts
@@ -43,7 +43,11 @@ function formatNumberToLocaleString(
   let isZero = false;
 
   if (!isFinite(value)) {
-    formattedText = getLocaleNumberSymbol(locale, NumberSymbol.Infinity);
+    // `Number.isNaN` (not `!isFinite`) so NaN uses the locale NaN symbol, not Infinity.
+    formattedText = getLocaleNumberSymbol(
+      locale,
+      Number.isNaN(value) ? NumberSymbol.NaN : NumberSymbol.Infinity,
+    );
   } else {
     let parsedNumber = parseNumber(value);
 
diff --git a/packages/common/test/i18n/format_number_spec.ts b/packages/common/test/i18n/format_number_spec.ts
index 0f42e955c69..3f3049982bc 100644
--- a/packages/common/test/i18n/format_number_spec.ts
+++ b/packages/common/test/i18n/format_number_spec.ts
@@ -38,6 +38,16 @@ describe('Format number', () => {
         expect(formatNumber(1e100, ɵDEFAULT_LOCALE_ID)).toEqual('1E+100');
       });
 
+      it('should format NaN and Infinity with locale symbols', () => {
+        expect(formatNumber(NaN, ɵDEFAULT_LOCALE_ID)).toEqual('NaN');
+        expect(formatNumber(Infinity, ɵDEFAULT_LOCALE_ID)).toEqual('∞');
+        expect(formatNumber(-Infinity, ɵDEFAULT_LOCALE_ID)).toEqual('-∞');
+        expect(formatPercent(NaN, ɵDEFAULT_LOCALE_ID)).toEqual('NaN%');
+        expect(formatPercent(Infinity, ɵDEFAULT_LOCALE_ID)).toEqual('∞%');
+        expect(formatCurrency(NaN, ɵDEFAULT_LOCALE_ID, '$')).toEqual('$NaN');
+        expect(formatCurrency(Infinity, ɵDEFAULT_LOCALE_ID, '$')).toEqual('$∞');
+      });
+
       it('should throw if minFractionDigits is explicitly higher than maxFractionDigits', () => {
         expect(() => formatNumber(1.1, ɵDEFAULT_LOCALE_ID, '3.4-2')).toThrowError(
           /is higher than the maximum/,