file_sys: serve an empty archive for missing Switch 2 system data

Switch 2 system data (ids 04...) is not part of Switch 1 firmware, and a
title aborts when it cannot mount it: Nintendo Switch Sports Resort asks
for 0400000000000849 right after boot. Synthesize an empty archive for
such ids (logged), so it boots to its first screens.
EDEN_NX2_EMPTY_SYSTEM_DATA=0 fails the request as before.

1 files changed, 14 insertions, 0 deletions

diff --git a/src/core/file_sys/system_archive/system_archive.cpp b/src/core/file_sys/system_archive/system_archive.cpp
index d47332a9d0..c3931b6f62 100644
--- a/src/core/file_sys/system_archive/system_archive.cpp
+++ b/src/core/file_sys/system_archive/system_archive.cpp
@@ -4,6 +4,8 @@
 // SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
+#include <cstdlib>
+
 #include "common/logging.h"
 #include "core/file_sys/romfs.h"
 #include "core/file_sys/system_archive/mii_model.h"
@@ -12,6 +14,7 @@
 #include "core/file_sys/system_archive/system_archive.h"
 #include "core/file_sys/system_archive/system_version.h"
 #include "core/file_sys/system_archive/time_zone_binary.h"
+#include "core/file_sys/vfs/vfs_vector.h"
 
 namespace FileSys::SystemArchive {
 
@@ -78,6 +81,17 @@ VirtualFile SynthesizeSystemArchive(const u64 title_id) {
     auto const desc = GetSystemArchive(title_id);
     if (desc.name == nullptr) {
         // Not a system archive Eden knows (fmt throws on a null string, ending the process).
+        // Switch 2 system data (ids 04...) is not installed with Switch 1 firmware, and titles
+        // abort when it cannot be mounted (Nintendo Switch Sports Resort, 0400000000000849):
+        // serve an empty archive. EDEN_NX2_EMPTY_SYSTEM_DATA=0 fails the request instead.
+        static const bool empty_nx2 = [] {
+            const char* setting = std::getenv("EDEN_NX2_EMPTY_SYSTEM_DATA");
+            return setting == nullptr || setting[0] != '0';
+        }();
+        if (empty_nx2 && (title_id >> 56) == 0x04) {
+            LOG_WARNING(Service_FS, "Empty archive for Switch 2 system data {:#016x}", title_id);
+            return CreateRomFS(std::make_shared<VectorVfsDirectory>());
+        }
         LOG_WARNING(Service_FS, "No system archive {:#016x} to synthesize", title_id);
         return nullptr;
     }