Properly handle mod-errors in on_shutdown

src/client/game.cpp

@@ -1300,7 +1300,8 @@ bool Game::createSingleplayerServer(const std::string &map_dir,
 		return false;
 	}
 
-	server = new Server(map_dir, gamespec, simple_singleplayer_mode, bind_addr, false);
+	server = new Server(map_dir, gamespec, simple_singleplayer_mode, bind_addr,
+			false, nullptr, error_message);
 	server->start();
 
 	return true;

src/server.cpp

@@ -213,7 +213,8 @@ Server::Server(
 		bool simple_singleplayer_mode,
 		Address bind_addr,
 		bool dedicated,
-		ChatInterface *iface
+		ChatInterface *iface,
+		std::string *on_shutdown_errmsg
 	):
 	m_bind_addr(bind_addr),
 	m_path_world(path_world),
@@ -232,6 +233,7 @@ Server::Server(
 	m_thread(new ServerThread(this)),
 	m_clients(m_con),
 	m_admin_chat(iface),
+	m_on_shutdown_errmsg(on_shutdown_errmsg),
 	m_modchannel_mgr(new ModChannelMgr())
 {
 	if (m_path_world.empty())
@@ -314,7 +316,18 @@ Server::~Server()
 
 		// Execute script shutdown hooks
 		infostream << "Executing shutdown hooks" << std::endl;
-		m_script->on_shutdown();
+		try {
+			m_script->on_shutdown();
+		} catch (ModError &e) {
+			errorstream << "ModError: " << e.what() << std::endl;
+			if (m_on_shutdown_errmsg) {
+				if (m_on_shutdown_errmsg->empty()) {
+					*m_on_shutdown_errmsg = std::string("ModError: ") + e.what();
+				} else {
+					*m_on_shutdown_errmsg += std::string("\nModError: ") + e.what();
+				}
+			}
+		}
 
 		infostream << "Server: Saving environment metadata" << std::endl;
 		m_env->saveMeta();

src/server.h

@@ -131,7 +131,8 @@ class Server : public con::PeerHandler, public MapEventReceiver,
 		bool simple_singleplayer_mode,
 		Address bind_addr,
 		bool dedicated,
-		ChatInterface *iface = nullptr
+		ChatInterface *iface = nullptr,
+		std::string *on_shutdown_errmsg = nullptr
 	);
 	~Server();
 	DISABLE_CLASS_COPY(Server);
@@ -596,6 +597,10 @@ class Server : public con::PeerHandler, public MapEventReceiver,
 	ChatInterface *m_admin_chat;
 	std::string m_admin_nick;
 
+	// if a mod-error occurs in the on_shutdown callback, the error message will
+	// be written into this
+	std::string *const m_on_shutdown_errmsg;
+
 	/*
 		Map edit event queue. Automatically receives all map edits.
 		The constructor of this class registers us to receive them through