Load GameUserSettings.ini from a UE4 build of a game in a UE5 build of a game

UE4GameUserSettingsLoader.cpp

#if PLATFORM_WINDOWS && !WITH_EDITOR && UE_BUILD_SHIPPING
static struct FUE4GameUserSettingsLoader
{
	FUE4GameUserSettingsLoader()
	{
		// This static constructor is called early enough that we can bind these required delegates before engine startup
		FCoreDelegates::TSCountPreLoadConfigFileRespondersDelegate().AddStatic(CountPreLoadConfigFileRespondersDelegate);
		FCoreDelegates::TSPreLoadConfigFileDelegate().AddStatic(PreLoadConfigFileDelegate);
		FCoreDelegates::TSPreSaveConfigFileDelegate().AddStatic(PreSaveConfigFileDelegate);
	}
	static bool Checked, UpgradeActive;
	static FString UE5Path, UE4Path;
	static void CountPreLoadConfigFileRespondersDelegate(const TCHAR* inipath, int32& responderCount)
	{
		if (!FCStringWide::Stristr(inipath, TEXT("GameUserSettings"))) return;
		const TCHAR* pWindows = FCString::Strrstr(inipath, TEXT("Windows"));
		if (!pWindows) return; // wrong path
		if (pWindows != inipath && pWindows[-1] != '/' && pWindows[-1] != '\\') return; // no slash before
		if (pWindows[7] != '/' && pWindows[7] != '\\') return; // no slash after
		if (!Checked)
		{
			(UE4Path = UE5Path = inipath).InsertAt((int32)(pWindows - inipath) + 7, TEXT("NoEditor")); // Change UE5's /Windows/ to UE4's /WindowsNoEditor/
			UpgradeActive = IFileManager::Get().FileExists(*UE4Path);
			Checked = true;
		}
		if (UpgradeActive) responderCount++;
	}
	static void PreLoadConfigFileDelegate(const TCHAR* inipath, FString& contents)
	{
		if (!UpgradeActive || UE5Path != inipath) return;
		FFileHelper::LoadFileToString(contents, *UE4Path);
	}
	static void PreSaveConfigFileDelegate(const TCHAR* inipath, const FString& contents, int32& savedCount)
	{
		if (!UpgradeActive || UE5Path != inipath) return;
		FFileHelper::SaveStringToFile(contents, *UE4Path, FFileHelper::EEncodingOptions::ForceUTF8WithoutBOM);
		savedCount++;
	}
} GDSIniUpgrader;
bool FUE4GameUserSettingsLoader::Checked, FUE4GameUserSettingsLoader::UpgradeActive;
FString FUE4GameUserSettingsLoader::UE5Path, FUE4GameUserSettingsLoader::UE4Path;
#endif