From e562a7d72cb7b1bf00840a10c97af37c833a3735 Mon Sep 17 00:00:00 2001
From: Wojtek Figat <wojtek@figat.pl>
Date: Fri, 31 Mar 2023 18:31:25 +0200
Subject: [PATCH] Fix loading C# assemblies from Mono AOT output

---
 Source/Engine/Scripting/ManagedCLR/MCore.cpp | 13 ++++++++++---
 Source/Engine/Scripting/Runtime/DotNet.cpp   | 10 ++++++++++
 Source/Engine/Scripting/Runtime/Mono.cpp     |  5 +++++
 3 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/Source/Engine/Scripting/ManagedCLR/MCore.cpp b/Source/Engine/Scripting/ManagedCLR/MCore.cpp
index bc2f934d6..f56eb566c 100644
--- a/Source/Engine/Scripting/ManagedCLR/MCore.cpp
+++ b/Source/Engine/Scripting/ManagedCLR/MCore.cpp
@@ -65,16 +65,23 @@ bool MAssembly::Load(const String& assemblyPath, const StringView& nativePath)
     PROFILE_CPU();
     ZoneText(*assemblyPath, assemblyPath.Length());
 
+    const String* pathPtr = &assemblyPath;
+    String path;
     if (!FileSystem::FileExists(assemblyPath))
     {
-        Log::FileNotFoundException ex(assemblyPath);
-        return true;
+        path = assemblyPath;
+        pathPtr = &path;
+        if (ResolveMissingFile(path))
+        {
+            Log::FileNotFoundException ex(assemblyPath);
+            return true;
+        }
     }
 
     const auto startTime = DateTime::NowUTC();
     OnLoading();
 
-    if (LoadImage(assemblyPath, nativePath))
+    if (LoadImage(*pathPtr, nativePath))
     {
         OnLoadFailed();
         return true;
diff --git a/Source/Engine/Scripting/Runtime/DotNet.cpp b/Source/Engine/Scripting/Runtime/DotNet.cpp
index f19fdf4d7..aab075306 100644
--- a/Source/Engine/Scripting/Runtime/DotNet.cpp
+++ b/Source/Engine/Scripting/Runtime/DotNet.cpp
@@ -761,6 +761,16 @@ MClass::MClass(const MAssembly* parentAssembly, void* handle, const char* name,
     classHandles.Add(handle, this);
 }
 
+bool MAssembly::ResolveMissingFile(String& assemblyPath) const
+{
+#if DOTNET_HOST_MONO
+    // Fallback to AOT-ed assembly location
+    assemblyPath = Globals::BinariesFolder / TEXT("Dotnet") / StringUtils::GetFileName(assemblyPath);
+    return !FileSystem::FileExists(assemblyPath);
+#endif
+    return true;
+}
+
 MClass::~MClass()
 {
     _methods.ClearDelete();
diff --git a/Source/Engine/Scripting/Runtime/Mono.cpp b/Source/Engine/Scripting/Runtime/Mono.cpp
index 363acdefb..3ebb92ccc 100644
--- a/Source/Engine/Scripting/Runtime/Mono.cpp
+++ b/Source/Engine/Scripting/Runtime/Mono.cpp
@@ -1170,6 +1170,11 @@ bool MAssembly::UnloadImage(bool isReloading)
     return false;
 }
 
+bool MAssembly::ResolveMissingFile(String& assemblyPath) const
+{
+    return true;
+}
+
 MClass::MClass(const MAssembly* parentAssembly, MonoClass* monoClass, const StringAnsi& fullname)
     : _assembly(parentAssembly)
     , _fullname(fullname)