Fix #10568: "can savegame be loaded check" failed in dedicated server

* If loading fails, it usually returns SL_REINIT which doesn't trigger check
 * If savegame has NewGRFs, it complains NewGRFs are not allowed in intro game

src/openttd.cpp

@@ -969,37 +969,51 @@ bool SafeLoad(const std::string &filename, SaveLoadOperation fop, DetailedFileTy
 
 	_game_mode = newgm;
 
-	switch (lf == nullptr ? SaveOrLoad(filename, fop, dft, subdir) : LoadWithFilter(lf)) {
+	SaveOrLoadResult result = (lf == nullptr) ? SaveOrLoad(filename, fop, dft, subdir) : LoadWithFilter(lf);
-		case SL_OK: return true;
+	if (result == SL_OK) return true;
-
+
-		case SL_REINIT:
+	if (_network_dedicated && ogm == GM_MENU) {
-			if (_network_dedicated) {
+		/*
-				/*
+		 * If we are a dedicated server *and* we just were in the menu, then we
-				 * We need to reinit a network map...
+		 * are loading the first savegame. If that fails, not starting the
-				 * We can't simply load the intro game here as that game has many
+		 * server is a better reaction than starting the server with a newly
-				 * special cases which make clients desync immediately. So we fall
+		 * generated map as it is quite likely to be started from a script.
-				 * back to just generating a new game with the current settings.
+		 */
-				 */
+		Debug(net, 0, "Loading requested map failed; closing server.");
-				Debug(net, 0, "Loading game failed, so a new (random) game will be started");
+		_exit_game = true;
-				MakeNewGame(false, true);
+		return false;
-				return false;
+	}
-			}
-			if (_network_server) {
-				/* We can't load the intro game as server, so disconnect first. */
-				NetworkDisconnect();
-			}
 
-			switch (ogm) {
+	if (result != SL_REINIT) {
-				default:
+		_game_mode = ogm;
-				case GM_MENU:   LoadIntroGame();      break;
+		return false;
-				case GM_EDITOR: MakeNewEditorWorld(); break;
+	}
-			}
+
-			return false;
+	if (_network_dedicated) {
+		/*
+		 * If we are a dedicated server, have already loaded/started a game,
+		 * and then loading the savegame fails in a manner that we need to
+		 * reinitialize everything. We must not fall back into the menu mode
+		 * with the intro game, as that is unjoinable by clients. So there is
+		 * nothing else to do than start a new game, as it might have failed
+		 * trying to reload the originally loaded savegame/scenario.
+		 */
+		Debug(net, 0, "Loading game failed, so a new (random) game will be started");
+		MakeNewGame(false, true);
+		return false;
+	}
+
+	if (_network_server) {
+		/* We can't load the intro game as server, so disconnect first. */
+		NetworkDisconnect();
+	}
 
+	switch (ogm) {
 		default:
-			_game_mode = ogm;
+		case GM_MENU:   LoadIntroGame();      break;
-			return false;
+		case GM_EDITOR: MakeNewEditorWorld(); break;
 	}
+	return false;
 }
 
 void SwitchToMode(SwitchMode new_mode)

src/video/dedicated_v.cpp

@@ -251,17 +251,6 @@ void VideoDriver_Dedicated::MainLoop()
 	/* If SwitchMode is SM_LOAD_GAME, it means that the user used the '-g' options */
 	if (_switch_mode != SM_LOAD_GAME) {
 		StartNewGameWithoutGUI(GENERATE_NEW_SEED);
-	} else {
-		/* First we need to test if the savegame can be loaded, else we will end up playing the
-		 *  intro game... */
-		if (SaveOrLoad(_file_to_saveload.name, _file_to_saveload.file_op, _file_to_saveload.detail_ftype, BASE_DIR) == SL_ERROR) {
-			/* Loading failed, pop out.. */
-			Debug(net, 0, "Loading requested map failed; closing server.");
-			return;
-		} else {
-			/* We can load this game, so go ahead */
-			_switch_mode = SM_LOAD_GAME;
-		}
 	}
 
 	this->is_game_threaded = false;