EmergeManager: Fix Lua mapgen override param handling

src/emerge.cpp

@@ -181,8 +181,15 @@ void EmergeManager::initMapgens(MapgenParams *mgparams) {
 
 	// Apply mapgen parameter overrides from Lua
 	if (luaoverride_params) {
-		if (luaoverride_params_modified & MGPARAMS_SET_MGNAME)
+		if (luaoverride_params_modified & MGPARAMS_SET_MGNAME) {
-			mgparams->mg_name = luaoverride_params->mg_name;
+			MapgenParams *mgp = setMapgenType(mgparams, luaoverride_params->mg_name);
+			if (!mgp) {
+				errorstream << "EmergeManager: Failed to set new mapgen name"
+							<< std::endl;
+			} else {
+				mgparams = mgp;
+			}
+		}
 
 		if (luaoverride_params_modified & MGPARAMS_SET_SEED)
 			mgparams->seed = luaoverride_params->seed;
@@ -202,18 +209,47 @@ void EmergeManager::initMapgens(MapgenParams *mgparams) {
 	// Create the mapgens
 	this->params = mgparams;
 	for (size_t i = 0; i != emergethread.size(); i++) {
-		mg = createMapgen(params->mg_name, 0, params);
+		mg = createMapgen(params->mg_name, i, params);
 		if (!mg) {
-			infostream << "EmergeManager: falling back to mapgen v6" << std::endl;
+			infostream << "EmergeManager: Falling back to Mapgen V6" << std::endl;
-			delete params;
+
-			params = createMapgenParams("v6");
+			params = setMapgenType(params, "v6");
-			mg = createMapgen("v6", 0, params);
+			mg = createMapgen(params->mg_name, i, params);
+			if (!mg) {
+				errorstream << "EmergeManager: CRITICAL ERROR: Failed to fall"
+					"back to Mapgen V6, not generating map" << std::endl;
+			}
 		}
 		mapgen.push_back(mg);
 	}
 }
 
 
+MapgenParams *EmergeManager::setMapgenType(MapgenParams *mgparams,
+	std::string newname) {
+	MapgenParams *newparams = createMapgenParams(newname);
+	if (!newparams) {
+		errorstream << "EmergeManager: Mapgen override failed" << std::endl;
+		return NULL;
+	}
+
+	newparams->mg_name     = newname;
+	newparams->seed        = mgparams->seed;
+	newparams->water_level = mgparams->water_level;
+	newparams->chunksize   = mgparams->chunksize;
+	newparams->flags       = mgparams->flags;
+
+	if (!newparams->readParams(g_settings)) {
+		errorstream << "EmergeManager: Mapgen override failed" << std::endl;
+		delete newparams;
+		return NULL;
+	}
+
+	delete mgparams;
+	return newparams;
+}
+
+
 Mapgen *EmergeManager::getCurrentMapgen() {
 	for (unsigned int i = 0; i != emergethread.size(); i++) {
 		if (emergethread[i]->IsSameThread())
@@ -229,6 +265,7 @@ void EmergeManager::triggerAllThreads() {
 		emergethread[i]->trigger();
 }
 
+
 bool EmergeManager::enqueueBlockEmerge(u16 peer_id, v3s16 p, bool allow_generate) {
 	std::map<v3s16, BlockEmergeData *>::const_iterator iter;
 	BlockEmergeData *bedata;
@@ -286,7 +323,7 @@ bool EmergeManager::enqueueBlockEmerge(u16 peer_id, v3s16 p, bool allow_generate
 int EmergeManager::getGroundLevelAtPoint(v2s16 p) {
 	if (mapgen.size() == 0 || !mapgen[0]) {
 		errorstream << "EmergeManager: getGroundLevelAtPoint() called"
-		" before mapgen initialized" << std::endl;
+			" before mapgen initialized" << std::endl;
 		return 0;
 	}
 
@@ -483,7 +520,7 @@ void *EmergeThread::Thread() {
 		MapBlock *block = NULL;
 		std::map<v3s16, MapBlock *> modified_blocks;
 
-		if (getBlockOrStartGen(p, &block, &data, allow_generate)) {
+		if (getBlockOrStartGen(p, &block, &data, allow_generate) && mapgen) {
 			{
 				ScopeProfiler sp(g_profiler, "EmergeThread: Mapgen::makeChunk", SPT_AVG);
 				TimeTaker t("mapgen::make_block()");

src/emerge.h

@@ -112,6 +112,7 @@ public:
 	~EmergeManager();
 
 	void initMapgens(MapgenParams *mgparams);
+	MapgenParams *setMapgenType(MapgenParams *mgparams, std::string newname);
 	Mapgen *getCurrentMapgen();
 	Mapgen *createMapgen(std::string mgname, int mgid,
 						MapgenParams *mgparams);