fix: make StringEqualsIgnoreCase constexpr (#1021)

* fix: make StringEqualsIgnoreCase constexpr

Move utils::StringEqualsIgnoreCase into the header as a constexpr function using an ASCII-only lowercase helper, so it can be used from constexpr contexts such as InfoString's comparators with newer MSVC toolsets.

* test: add StringEqualsIgnoreCase tests

src/Utils/Utils/StringUtils.cpp

@@ -4,14 +4,6 @@
 #include <cctype>
 #include <sstream>
 
-namespace
-{
-    bool ichar_equals(const char a, const char b)
-    {
-        return std::tolower(static_cast<unsigned char>(a)) == std::tolower(static_cast<unsigned char>(b));
-    }
-} // namespace
-
 namespace utils
 {
     std::string EscapeStringForQuotationMarks(const std::string_view& str)
@@ -123,11 +115,6 @@ namespace utils
             c = static_cast<char>(toupper(static_cast<unsigned char>(c)));
     }
 
-    bool StringEqualsIgnoreCase(std::string_view lhs, std::string_view rhs)
-    {
-        return std::ranges::equal(lhs, rhs, ichar_equals);
-    }
-
     void StringTrimL(std::string& str)
     {
         str.erase(str.begin(),

src/Utils/Utils/StringUtils.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <algorithm>
 #include <string>
 #include <string_view>
 #include <vector>
@@ -20,7 +21,20 @@ namespace utils
     void MakeStringUpperCase(char* str);
     void MakeStringUpperCase(std::string& str);
 
-    bool StringEqualsIgnoreCase(std::string_view lhs, std::string_view rhs);
+    constexpr char CharToLowerAscii(const char c)
+    {
+        return c >= 'A' && c <= 'Z' ? static_cast<char>(c - 'A' + 'a') : c;
+    }
+
+    constexpr bool StringEqualsIgnoreCase(const std::string_view lhs, const std::string_view rhs)
+    {
+        return std::ranges::equal(lhs,
+                                  rhs,
+                                  [](const char a, const char b)
+                                  {
+                                      return CharToLowerAscii(a) == CharToLowerAscii(b);
+                                  });
+    }
 
     void StringTrimL(std::string& str);
     void StringTrimR(std::string& str);

test/CommonTests/Utils/StringUtilsTests.cpp

@@ -0,0 +1,23 @@
+#include "Utils/StringUtils.h"
+
+#include <catch2/catch_test_macros.hpp>
+
+static_assert(utils::StringEqualsIgnoreCase("", ""));
+static_assert(utils::StringEqualsIgnoreCase("Hello World", "hELLO wORLD"));
+static_assert(!utils::StringEqualsIgnoreCase("Hello", "Hello World"));
+static_assert(!utils::StringEqualsIgnoreCase("[", "{"));
+
+TEST_CASE("StringUtils: StringEqualsIgnoreCase", "[stringutils]")
+{
+    SECTION("matches strings that only differ in case")
+    {
+        REQUIRE(utils::StringEqualsIgnoreCase("mp_rust", "MP_Rust"));
+        REQUIRE(utils::StringEqualsIgnoreCase("ABCDEFGHIJKLMNOPQRSTUVWXYZ", "abcdefghijklmnopqrstuvwxyz"));
+    }
+
+    SECTION("does not match different strings")
+    {
+        REQUIRE_FALSE(utils::StringEqualsIgnoreCase("mp_rust", "mp_rust2"));
+        REQUIRE_FALSE(utils::StringEqualsIgnoreCase("@", "`"));
+    }
+}