toLocaleLowerCase and toLocaleUpperCase do not throw on empty string

Constellation · Constellation · commit e99f5f69bf90 · 2023-01-23T14:21:23.000-08:00
https://bugs.webkit.org/show_bug.cgi?id=250903 rdar://104568214 Reviewed by Alexey Shvayka. This patch aligns our toLocaleLowerCase and toLocaleUpperCase for invalid locale tag + empty string edge case to the spec. We should optimize empty string case only when locale is not specified. * JSTests/stress/empty-string-locale-case-convert.js: Added. (shouldThrow): * Source/JavaScriptCore/runtime/StringPrototype.cpp: (JSC::toLocaleCase): Canonical link: https://commits.webkit.org/259242@main
diff --git a/JSTests/stress/empty-string-locale-case-convert.js b/JSTests/stress/empty-string-locale-case-convert.js
@@ -0,0 +1,27 @@
+function shouldThrow(func, errorMessage) {
+    var errorThrown = false;
+    var error = null;
+    try {
+        func();
+    } catch (e) {
+        errorThrown = true;
+        error = e;
+    }
+    if (!errorThrown)
+        throw new Error('not thrown');
+    if (String(error) !== errorMessage)
+        throw new Error(`bad error: ${String(error)}`);
+}
+
+shouldThrow(() => {
+    'a'.toLocaleLowerCase('');
+}, `RangeError: invalid language tag: `);
+shouldThrow(() => {
+    'a'.toLocaleUpperCase('');
+}, `RangeError: invalid language tag: `);
+shouldThrow(() => {
+    ''.toLocaleLowerCase('');
+}, `RangeError: invalid language tag: `);
+shouldThrow(() => {
+    ''.toLocaleUpperCase('');
+}, `RangeError: invalid language tag: `);
diff --git a/Source/JavaScriptCore/runtime/StringPrototype.cpp b/Source/JavaScriptCore/runtime/StringPrototype.cpp
@@ -1370,12 +1370,14 @@ static EncodedJSValue toLocaleCase(JSGlobalObject* globalObject, CallFrame* call
     // 3. ReturnIfAbrupt(S).
     RETURN_IF_EXCEPTION(scope, encodedJSValue());
 
+    JSValue localeValue = callFrame->argument(0);
+
     // Optimization for empty strings.
-    if (s.isEmpty())
+    if (s.isEmpty() && localeValue.isUndefined())
         return JSValue::encode(sVal);
 
     // 4. Let requestedLocales be CanonicalizeLocaleList(locales).
-    Vector<String> requestedLocales = canonicalizeLocaleList(globalObject, callFrame->argument(0));
+    Vector<String> requestedLocales = canonicalizeLocaleList(globalObject, localeValue);
 
     // 5. ReturnIfAbrupt(requestedLocales).
     RETURN_IF_EXCEPTION(scope, encodedJSValue());
