From 2dc9ae00af130968af1f98cff4c39bf017149676 Mon Sep 17 00:00:00 2001
From: Timothy Flynn <trflynn89@pm.me>
Date: Tue, 27 Jul 2021 14:02:47 -0400
Subject: [PATCH] LibJS: Use special case folding for
 String.prototype.to{Lower,Upper}Case

Note we still have one String.prototype.toLowerCase test262 failure due
to not yet parsing WordBreakProperty.txt.
---
 .../LibJS/Runtime/StringPrototype.cpp         | 26 ++++++-------------
 .../String/String.prototype.toLowerCase.js    | 15 +++++++++++
 .../String/String.prototype.toUpperCase.js    | 17 ++++++++++++
 3 files changed, 40 insertions(+), 18 deletions(-)

diff --git a/Userland/Libraries/LibJS/Runtime/StringPrototype.cpp b/Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
index 08e3ea63d8..fcbde841cb 100644
--- a/Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
@@ -381,33 +381,23 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::index_of)
 // 22.1.3.26 String.prototype.toLowerCase ( ), https://tc39.es/ecma262/#sec-string.prototype.tolowercase
 JS_DEFINE_NATIVE_FUNCTION(StringPrototype::to_lowercase)
 {
-    auto string = utf16_string_from(vm, global_object);
-    if (vm.exception())
+    auto string = ak_string_from(vm, global_object);
+    if (!string.has_value())
         return {};
 
-    Utf16View utf16_string_view { string };
-    StringBuilder builder;
-
-    for (auto code_point : utf16_string_view)
-        builder.append_code_point(Unicode::to_unicode_lowercase(code_point));
-
-    return js_string(vm, builder.to_string());
+    auto lowercase = Unicode::to_unicode_lowercase_full(*string);
+    return js_string(vm, move(lowercase));
 }
 
 // 22.1.3.28 String.prototype.toUpperCase ( ), https://tc39.es/ecma262/#sec-string.prototype.touppercase
 JS_DEFINE_NATIVE_FUNCTION(StringPrototype::to_uppercase)
 {
-    auto string = utf16_string_from(vm, global_object);
-    if (vm.exception())
+    auto string = ak_string_from(vm, global_object);
+    if (!string.has_value())
         return {};
 
-    Utf16View utf16_string_view { string };
-    StringBuilder builder;
-
-    for (auto code_point : utf16_string_view)
-        builder.append_code_point(Unicode::to_unicode_uppercase(code_point));
-
-    return js_string(vm, builder.to_string());
+    auto uppercase = Unicode::to_unicode_uppercase_full(*string);
+    return js_string(vm, move(uppercase));
 }
 
 // 22.1.3.27 String.prototype.toString ( ), https://tc39.es/ecma262/#sec-string.prototype.tostring
diff --git a/Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.toLowerCase.js b/Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.toLowerCase.js
index da176af6d8..bf3cc754d5 100644
--- a/Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.toLowerCase.js
+++ b/Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.toLowerCase.js
@@ -11,3 +11,18 @@ test("basic functionality", () => {
 
     expect(("b" + "a" + +"a" + "a").toLowerCase()).toBe("banana");
 });
+
+test("special case folding", () => {
+    expect("\u00DF".toLowerCase()).toBe("\u00DF");
+    expect("\u0130".toLowerCase()).toBe("\u0069\u0307");
+    expect("\uFB00".toLowerCase()).toBe("\uFB00");
+    expect("\uFB01".toLowerCase()).toBe("\uFB01");
+    expect("\uFB02".toLowerCase()).toBe("\uFB02");
+    expect("\uFB03".toLowerCase()).toBe("\uFB03");
+    expect("\uFB04".toLowerCase()).toBe("\uFB04");
+    expect("\uFB05".toLowerCase()).toBe("\uFB05");
+    expect("\uFB06".toLowerCase()).toBe("\uFB06");
+    expect("\u1FB7".toLowerCase()).toBe("\u1FB7");
+    expect("\u1FC7".toLowerCase()).toBe("\u1FC7");
+    expect("\u1FF7".toLowerCase()).toBe("\u1FF7");
+});
diff --git a/Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.toUpperCase.js b/Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.toUpperCase.js
index 51526733c8..42631a4112 100644
--- a/Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.toUpperCase.js
+++ b/Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.toUpperCase.js
@@ -11,3 +11,20 @@ test("basic functionality", () => {
 
     expect(("b" + "a" + +"n" + "a").toUpperCase()).toBe("BANANA");
 });
+
+test("special case folding", () => {
+    expect("\u00DF".toUpperCase()).toBe("\u0053\u0053");
+    expect("\u0130".toUpperCase()).toBe("\u0130");
+    expect("\uFB00".toUpperCase()).toBe("\u0046\u0046");
+    expect("\uFB01".toUpperCase()).toBe("\u0046\u0049");
+    expect("\uFB02".toUpperCase()).toBe("\u0046\u004C");
+    expect("\uFB03".toUpperCase()).toBe("\u0046\u0046\u0049");
+    expect("\uFB04".toUpperCase()).toBe("\u0046\u0046\u004C");
+    expect("\uFB05".toUpperCase()).toBe("\u0053\u0054");
+    expect("\uFB06".toUpperCase()).toBe("\u0053\u0054");
+    expect("\u0390".toUpperCase()).toBe("\u0399\u0308\u0301");
+    expect("\u03B0".toUpperCase()).toBe("\u03A5\u0308\u0301");
+    expect("\u1FB7".toUpperCase()).toBe("\u0391\u0342\u0399");
+    expect("\u1FC7".toUpperCase()).toBe("\u0397\u0342\u0399");
+    expect("\u1FF7".toUpperCase()).toBe("\u03A9\u0342\u0399");
+});