Merge PR #716: Fix Unicode paths on Windows

Preserve native Windows paths for filesystem operations, command-line options,
and game icons. Complete Unicode handling in recursive file listings and file
logging, restore unmounting by host directory, and extend regression coverage.

Original implementation by Augusto Domingos (@AghastyGD); retain all five of
his PR commits and include the reviewed follow-up fixes.

Closes #714

Co-authored-by: Augusto Domingos <augustodomingosvasco@gmail.com>

tests/KernelFileSystemTests.cpp

@@ -4,12 +4,14 @@
 #include "common/logging/log.h"
 #include "common/subsystems.h"
 #include "common/threads.h"
+#include "common/stringUtils.h"
 #include "graphics/presentation/window/windowInternal.h"
 #include "kernel/fileSystem.h"
 #include "libs/errno.h"
 #include "libs/network.h"
 #include "loader/symbolDatabase.h"
 
+#include <algorithm>
 #include <array>
 
 #include <chrono>
@@ -153,6 +155,94 @@ void CheckMountRoot(const std::filesystem::path &root) {
     }
   }
   FileSystem::Umount("/app0");
+  Check(FileSystem::GetRealFilename("/app0/rpf.cache") == "/app0/rpf.cache",
+        "unmount by guest path");
+  for (const auto &folder : {root, root / ""}) {
+    for (const auto &host : {root, root / ""}) {
+      FileSystem::Mount(folder, "/app0");
+      FileSystem::Umount(Common::PathToGenericString(host));
+      Check(FileSystem::GetRealFilename("/app0/rpf.cache") == "/app0/rpf.cache",
+            "unmount by host path with or without trailing separator");
+    }
+  }
+}
+
+void CheckUnicodePaths(const std::filesystem::path &root) {
+  constexpr std::string_view HostDirectory =
+      "Test\xc3\xa9-\xe6\x97\xa5\xe6\x9c\xac\xe8\xaa\x9e";
+  constexpr std::string_view GuestFilename =
+      "asset-\xc3\xa9-\xe6\x97\xa5\xe6\x9c\xac\xe8\xaa\x9e.bin";
+
+  const auto unicode_root =
+      root / Common::PathFromUtf8(HostDirectory);
+  const auto nested_root = unicode_root / "nested";
+
+  Check(Common::File::CreateDirectories(nested_root),
+        "create nested Unicode host directory");
+
+  CheckMountRoot(nested_root);
+
+  const auto native_file =
+      nested_root / Common::PathFromUtf8(GuestFilename);
+
+  Common::File fixture;
+  Check(fixture.Create(native_file), "create Unicode filename");
+  fixture.Close();
+
+  for (const auto &directory : {unicode_root, std::filesystem::relative(unicode_root)}) {
+    // A Windows temporary directory may be on a different drive from the working directory.
+    if (directory.empty()) {
+      continue;
+    }
+    const auto files = Common::File::FindFiles(directory);
+    const auto relative_file =
+        std::filesystem::path(u8"nested/asset-\u00e9-\u65e5\u672c\u8a9e.bin");
+    Check(std::any_of(files.begin(), files.end(), [&](const auto &file) {
+            return file.path_with_name.lexically_normal() ==
+                       (directory / relative_file).lexically_normal() &&
+                   file.rel_path_with_name == relative_file;
+          }), "recursive enumeration preserves native and relative Unicode paths");
+  }
+  const auto entries = Common::File::GetDirEntries(nested_root);
+  Check(std::any_of(entries.begin(), entries.end(), [&](const auto &entry) {
+          return entry.is_file && entry.name == GuestFilename;
+        }), "directory enumeration returns UTF-8 filenames");
+
+  FileSystem::Mount(nested_root, "/app0");
+
+  const auto guest_file =
+      std::string("/app0/") + std::string(GuestFilename);
+
+  Check(FileSystem::GetRealFilename(guest_file) == native_file,
+        "resolve Unicode guest path");
+
+  const int fd = FileSystem::KernelOpen(guest_file.c_str(), 0, 0);
+  Check(fd >= 3, "open Unicode guest path");
+  Check(FileSystem::KernelClose(fd) == OK,
+        "close Unicode guest path");
+
+  FileSystem::Umount("/app0");
+}
+
+void CheckUnicodeLogPath(const std::filesystem::path &root) {
+  Config::ConfigOptions options;
+  options.printf_direction = Config::LogDirection::File;
+  options.printf_output_file = root / u8"logs-\u65e5\u672c\u8a9e-\U0001f600" / u8"log-\u00e9.txt";
+  Config::Load(options);
+  Log::Initialize();
+  constexpr std::string_view Payload = "Unicode log path\n";
+  Log::Write(Payload);
+  Log::Shutdown();
+
+  Common::File result(options.printf_output_file, Common::File::Mode::Read);
+  Check(!result.IsInvalid(), "open Unicode log file");
+  const auto data = result.ReadWholeBuffer();
+  Check(data.size() == Payload.size() &&
+            std::memcmp(data.data(), Payload.data(), data.size()) == 0,
+        "Unicode log file contains output");
+  options.printf_direction = Config::LogDirection::Silent;
+  Config::Load(options);
+  Log::Initialize();
 }
 
 void CheckDirectoryStream(const std::filesystem::path &root) {
@@ -414,6 +504,8 @@ int main() {
   TempDirectory temporary;
   FileSystem::Initialize();
   CheckMountRoot(temporary.Path());
+  CheckUnicodePaths(temporary.Path());
+  CheckUnicodeLogPath(temporary.Path());
   CheckDirectoryStream(temporary.Path());
   CheckAprPaths(temporary.Path());
   FileSystem::Mount(temporary.Path(), "/savedata0");