Mono/C#: Fix load hook not called for some assemblies on domain reload

modules/mono/mono_gd/gd_mono_assembly.cpp

@@ -277,12 +277,25 @@ no_pdb:
 
 #endif
 
+	bool need_manual_load_hook = mono_image_get_assembly(image) != nullptr; // Re-using an existing image with an assembly loaded
+
 	status = MONO_IMAGE_OK;
 
 	MonoAssembly *assembly = mono_assembly_load_from_full(image, image_filename.utf8().get_data(), &status, p_refonly);
 
 	ERR_FAIL_COND_V_MSG(status != MONO_IMAGE_OK || !assembly, nullptr, "Failed to load assembly for image");
 
+	if (need_manual_load_hook) {
+		// For some reason if an assembly survived domain reloading (maybe because it's referenced somewhere else),
+		// the mono internal search hook don't detect it, yet mono_image_open_from_data_with_name re-uses the image
+		// and assembly, and mono_assembly_load_from_full doesn't call the load hook. We need to call it manually.
+		String name = String::utf8(mono_assembly_name_get_name(mono_assembly_get_name(assembly)));
+		bool has_extension = name.ends_with(".dll") || name.ends_with(".exe");
+		GDMonoAssembly *loaded_asm = GDMono::get_singleton()->get_loaded_assembly(has_extension ? name.get_basename() : name);
+		if (!loaded_asm)
+			assembly_load_hook(assembly, nullptr);
+	}
+
 	// Decrement refcount which was previously incremented by mono_image_open_from_data_with_name
 	mono_image_close(image);