[ServerModLoader] Dependencies: OK.

source/server/lua/ServerModLoader.cpp

@@ -38,7 +38,12 @@ namespace fs = ghc::filesystem;
 struct ModEntry {
 	fs::path path;
 	std::string id;
+
 	std::vector<std::string> dependencies;
+	std::vector<ModEntry *> requiredBy;
+
+	bool isLoaded = false;
+	bool isValid = true;
 };
 
 void ServerModLoader::loadMods() {
@@ -93,58 +98,75 @@ void ServerModLoader::loadMods() {
 			gkError() << ("The mod at '" + entry.path().string() + "' doesn't contain a 'config.lua' file.").c_str();
 	}
 
-	{
-		// Small BFS to check cyclic dependencies
-		for (auto &modit : mods) {
-			std::queue<std::string> queue;
-			queue.emplace(modit.first);
-			while (!queue.empty()) {
-				std::string modID = queue.front();
-				queue.pop();
-
-				auto it = mods.find(modID);
-				if (it == mods.end())
-					break;
+	std::queue<ModEntry *> dependencyTree;
+
+	// Small BFS to check cyclic dependencies and build the dependency tree
+	for (auto &modit : mods) {
+		std::queue<ModEntry *> queue;
+		queue.emplace(&modit.second);
+		while (!queue.empty()) {
+			ModEntry *mod = queue.front();
+			queue.pop();
 
-				for (auto &dep : it->second.dependencies) {
-					if (dep == modit.first)
-						throw EXCEPTION("Cyclic dependency detected for mod '"
-								+ modit.second.id + "' in mod '" + it->second.id + "'");
+			if (mod->dependencies.empty())
+				dependencyTree.emplace(mod);
+
+			for (const std::string &dependencyID : mod->dependencies) {
+				if (dependencyID == modit.second.id) {
+					gkError() << ("Cyclic dependency detected for mod '" + modit.second.id + "' in mod '" + mod->id + "'").c_str();
+					mod->isValid = false;
+					break;
+				}
 
-					queue.emplace(dep);
+				auto it = mods.find(dependencyID);
+				if (it != mods.end()) {
+					it->second.requiredBy.emplace_back(mod);
+					queue.emplace(&it->second);
+				}
+				else {
+					gkError() << ("Mod '" + mod->id + "' cannot be loaded: Missing dependency '" + dependencyID + "'").c_str();
+					mod->isValid = false;
 				}
 			}
 		}
 	}
 
-	// TODO: Build a dependency graph
-	//       Two types of dependencies should be handled
+	// TODO: Two types of dependencies should be handled
 	//       - Required (cyclic depedencies not handled)
 	//       - Optional (cyclic dependencies handled)
 
-	// TODO: Load 'mods/config.lua' to let user define a preferred mod path (see #82)
-
 	m_scriptEngine.init();
 	m_scriptEngine.luaCore().setModLoader(this);
 
-	for (auto &it : mods) {
-		if (fs::exists(it.second.path.string() + "/init.lua")) {
-			fs::current_path(it.second.path.string());
+	while (!dependencyTree.empty()) {
+		ModEntry *mod = dependencyTree.front();
+		dependencyTree.pop();
+
+		if (mod->isLoaded || !mod->isValid) continue;
+
+		if (fs::exists(mod->path.string() + "/init.lua")) {
+			fs::current_path(mod->path.string());
 
 			try {
 				m_scriptEngine.lua().safe_script_file("init.lua");
 			}
 			catch (const sol::error &e) {
-				gkError() << "Error: Failed to load mod at" << it.second.path.string();
+				gkError() << "Error: Failed to load mod at" << mod->path.string();
 				gkError() << e.what();
 			}
 
 			fs::current_path(basePath);
 
-			gkInfo() << "Mod" << it.first << "loaded";
+			gkInfo() << "Mod" << mod->id << "loaded";
 		}
 		else
-			gkError() << ("The mod at '" + it.second.path.string() + "' doesn't contain an 'init.lua' file.").c_str();
+			gkError() << ("The mod at '" + mod->path.string() + "' doesn't contain an 'init.lua' file.").c_str();
+
+		mod->isLoaded = true;
+
+		for (ModEntry *entry : mod->requiredBy) {
+			dependencyTree.emplace(entry);
+		}
 	}
 
 	for (auto &it : m_mods) {