[Editor]: Stop Loading .Net Project Assembly when TOOLS is not Defined

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/GodotPluginsInitializerGenerator.cs

@@ -52,6 +52,12 @@ private static godot_bool InitializeFromGameProject(IntPtr godotDllHandle, IntPt
                 return false.ToGodotBool();
             }
         }
+
+#if TOOLS
+#pragma warning disable CS0169
+        private static bool ToolsDefined;
+#pragma warning restore CS0169
+#endif
     }
 }
 ";

modules/mono/glue/GodotSharp/GodotPlugins/Main.cs

@@ -131,33 +131,49 @@ private static unsafe godot_bool InitializeFromEngine(IntPtr godotDllHandle, god
         [StructLayout(LayoutKind.Sequential)]
         private struct PluginsCallbacks
         {
-            public unsafe delegate* unmanaged<char*, godot_string*, godot_bool> LoadProjectAssemblyCallback;
+            public unsafe delegate* unmanaged<char*, godot_string*, godot_string*, godot_bool*, godot_bool> LoadProjectAssemblyCallback;
             public unsafe delegate* unmanaged<char*, IntPtr, int, IntPtr> LoadToolsAssemblyCallback;
             public unsafe delegate* unmanaged<godot_bool> UnloadProjectPluginCallback;
         }
 
         [UnmanagedCallersOnly]
-        private static unsafe godot_bool LoadProjectAssembly(char* nAssemblyPath, godot_string* outLoadedAssemblyPath)
+        private static unsafe godot_bool LoadProjectAssembly(char* nAssemblyPath, godot_string* outLoadedAssemblyPath, godot_string* outFailedReason, godot_bool* shouldRetry)
         {
             try
             {
                 if (_projectLoadContext != null)
                     return godot_bool.True; // Already loaded
 
+                *shouldRetry = godot_bool.False;
                 string assemblyPath = new(nAssemblyPath);
 
                 (var projectAssembly, _projectLoadContext) = LoadPlugin(assemblyPath, isCollectible: _editorHint);
 
                 string loadedAssemblyPath = _projectLoadContext.AssemblyLoadedPath ?? assemblyPath;
                 *outLoadedAssemblyPath = Marshaling.ConvertStringToNative(loadedAssemblyPath);
 
+                // This generated field is here to ensure that
+                // the developer do not drop the TOOLS compiler preprocessor
+                // from their csproj, which breaks the C# Editor Functionality.
+                var isToolsDefinedField =
+                    projectAssembly
+                        .GetType("GodotPlugins.Game.Main")?
+                        .GetField("ToolsDefined", BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic);
+
+                if (isToolsDefinedField == null)
+                {
+                    *outFailedReason = Marshaling.ConvertStringToNative("The csproj was missing the `TOOLS` compiler symbol, which is required for C# editor functionality. Please modify the csproj file and rebuild the C# project, check https://github.com/godotengine/godot/issues/98124 for more information.");
+                    return godot_bool.False;
+                }
+
                 ScriptManagerBridge.LookupScriptsInAssembly(projectAssembly);
 
                 return godot_bool.True;
             }
             catch (Exception e)
             {
                 Console.Error.WriteLine(e);
+                *outFailedReason = Marshaling.ConvertStringToNative(e.Message);
                 return godot_bool.False;
             }
         }

modules/mono/mono_gd/gd_mono.cpp

@@ -605,9 +605,15 @@ void GDMono::_try_load_project_assembly() {
 	// Load the project's main assembly. This doesn't necessarily need to succeed.
 	// The game may not be using .NET at all, or if the project does use .NET and
 	// we're running in the editor, it may just happen to be it wasn't built yet.
-	if (!_load_project_assembly()) {
+	String error_message;
+	bool should_retry;
+	if (!_load_project_assembly(&error_message, &should_retry)) {
 		if (OS::get_singleton()->is_stdout_verbose()) {
-			print_error(".NET: Failed to load project assembly");
+			if (error_message.is_empty()) {
+				print_error(".NET: Failed to load project assembly");
+			} else {
+				print_error(".NET: Failed to load project assembly: " + error_message);
+			}
 		}
 	}
 }
@@ -624,19 +630,22 @@ void GDMono::_init_godot_api_hashes() {
 }
 
 #ifdef TOOLS_ENABLED
-bool GDMono::_load_project_assembly() {
+bool GDMono::_load_project_assembly(String *p_error_message, bool *p_should_retry) {
+	*p_should_retry = true;
+
 	String assembly_name = path::get_csharp_project_name();
 
 	String assembly_path = GodotSharpDirs::get_res_temp_assemblies_dir()
 								   .path_join(assembly_name + ".dll");
 	assembly_path = ProjectSettings::get_singleton()->globalize_path(assembly_path);
 
 	if (!FileAccess::exists(assembly_path)) {
+		*p_error_message = String("Assembly Path \"" + assembly_path + "\" does not exist");
 		return false;
 	}
 
 	String loaded_assembly_path;
-	bool success = plugin_callbacks.LoadProjectAssemblyCallback(assembly_path.utf16(), &loaded_assembly_path);
+	bool success = plugin_callbacks.LoadProjectAssemblyCallback(assembly_path.utf16(), &loaded_assembly_path, p_error_message, p_should_retry);
 
 	if (success) {
 		project_assembly_path = loaded_assembly_path.simplify_path();
@@ -679,10 +688,19 @@ Error GDMono::reload_project_assemblies() {
 
 	// Load the project's main assembly. Here, during hot-reloading, we do
 	// consider failing to load the project's main assembly to be an error.
-	if (!_load_project_assembly()) {
-		ERR_PRINT_ED(".NET: Failed to load project assembly.");
+	String error_message;
+	bool should_retry;
+	if (!_load_project_assembly(&error_message, &should_retry)) {
+		if (error_message.is_empty()) {
+			ERR_PRINT_ED(".NET: Failed to load project assembly.");
+		} else {
+			ERR_PRINT_ED(".NET: Failed to load project assembly: " + error_message);
+		}
+		if (!should_retry) {
+			project_load_failure_count = (int)GLOBAL_GET("dotnet/project/assembly_reload_attempts");
+		}
 		reload_failure();
-		return ERR_CANT_OPEN;
+		return FAILED;
 	}
 
 	if (project_load_failure_count > 0) {

modules/mono/mono_gd/gd_mono.h

@@ -47,7 +47,7 @@ namespace gdmono {
 
 #ifdef TOOLS_ENABLED
 struct PluginCallbacks {
-	using FuncLoadProjectAssemblyCallback = bool(GD_CLR_STDCALL *)(const char16_t *, String *);
+	using FuncLoadProjectAssemblyCallback = bool(GD_CLR_STDCALL *)(const char16_t *, String *, String *, bool *);
 	using FuncLoadToolsAssemblyCallback = Object *(GD_CLR_STDCALL *)(const char16_t *, const void **, int32_t);
 	using FuncUnloadProjectPluginCallback = bool(GD_CLR_STDCALL *)();
 	FuncLoadProjectAssemblyCallback LoadProjectAssemblyCallback = nullptr;
@@ -73,7 +73,7 @@ class GDMono {
 #endif
 
 #ifdef TOOLS_ENABLED
-	bool _load_project_assembly();
+	bool _load_project_assembly(String *p_error_message, bool *p_should_retry);
 	void _try_load_project_assembly();
 #endif