MP Lobby: actually properly display required addon names

Turns out I implemented ba9274e incorrectly. I had naively thought
that the name= key in both instances (required addon parsing and version compatibility check) was
the right key to use. I was wrong.

In the case of required addon parsing, it turns out there was no name= key in the first place, so
the "Missing addon: foo" message was using the addon id. In the case of the version compatibility
check, it was using the *content* name, not the *addon* name. For example, it was displaying the name
of a given modification shipped with an addon, but not the actual addon that shipped it. That was
definitely not what we wanted.

To fix this issue, I've added a name field to the config for required addons. This is populated with
the addon_title= key (see below) of the required addon when the host creates a game. Do note the list
of required addons is sent over the network. In the case of the version compatibility check, I made
use of the same addon_title= key, except taken from the player's local config (this is because the
version compatibility check only happens if you already have the given modification/era/etc installed
from an addon).

The addon_title= key itself is added to an era/mod/scenario/campaign/etc's config when addons are
loaded, same as the addon_id= and addon_version= key. Currently it takes its value from _info.cfg's
[info] title= field. If that isn't present, it falls back to addon_id=.

src/game_config_manager.cpp

@@ -339,9 +339,11 @@ void game_config_manager::load_game_config(FORCE_RELOAD_CONFIG force_reload,
 	paths_manager_.set_paths(game_config());
 }
 
-struct addon_source {
+struct addon_source
+{
 	std::string main_cfg;
 	std::string addon_id;
+	std::string addon_title;
 	version_info version;
 };
 
@@ -394,21 +396,37 @@ void game_config_manager::load_addons_cfg()
 		addon.main_cfg = main_cfg;
 		addon.addon_id = addon_id;
 
-		if (filesystem::file_exists(main_cfg)) {
-			if (filesystem::file_exists(info_cfg)) {
+		if(filesystem::file_exists(main_cfg)) {
+			if(filesystem::file_exists(info_cfg)) {
 				config info;
 				cache_.get_config(info_cfg, info);
-				const config info_tag = info.child_or_empty("info");
+
+				const config& info_tag = info.child_or_empty("info");
+
 				std::string core = info_tag["core"];
-				if (core.empty()) core = "default";
-				if ( !info_tag.empty() && // Don't skip addons which have no [info], they are most likely manually installed.
-						info_tag["type"] != "core" && // Don't skip cores, we want them selectable at all times.
-						core != preferences::core_id() // Don't skip addons matching our current core.
-				) {
-					continue; // Skip add-ons not matching our current core.
+				if(core.empty()) {
+					core = "default";
+				}
+
+				addon.addon_title = info_tag["title"];
+
+				// Skip add-ons not matching our current core.
+				//
+				// Don't skip:
+				// - addons which have no [info], they are most likely manually installed.
+				// - cores, we want them selectable at all times.
+				// - addons matching our current core.
+				if(!info_tag.empty() && info_tag["type"] != "core" && core != preferences::core_id()) {
+					continue;
 				}
 			}
 
+			// Fall back to ID if no title was found (most likely in the case of missing _info.cfg).
+			// TODO: account for case where _info.cfg is missing but a .pbl file is present.
+			if(addon.addon_title.empty()) {
+				addon.addon_title = addon_id;
+			}
+
 			// Ask the addon manager to find version info for us (from info, pbl file)
 			addon.version = get_addon_version_info(addon_id);
 			addons_to_load.push_back(addon);
@@ -429,6 +447,7 @@ void game_config_manager::load_addons_cfg()
 				if(tags_with_addon_id.count(child.key) > 0) {
 					auto& cfg = child.cfg;
 					cfg["addon_id"] = addon.addon_id;
+					cfg["addon_title"] = addon.addon_title;
 					// Note that this may reformat the string in a canonical form.
 					cfg["addon_version"] = addon.version.str();
 				}

src/game_initialization/lobby_data.cpp

@@ -474,18 +474,12 @@ game_info::ADDON_REQ game_info::check_addon_version_compatibility(const config&
 
 		remote_min_ver = std::min(remote_min_ver, remote_ver);
 
-		// Use content name if provided, else fall back on the addon id.
-		// TODO: should this use t_string?
-		const std::string content_name = local_item.has_attribute("name")
-			? local_item["name"].str()
-			: local_item["addon_id"].str();
-
 		// Check if the host is too out of date to play.
 		if(local_min_ver > remote_ver) {
 			r.outcome = CANNOT_SATISFY;
 
 			r.message = vgettext("The host's version of <i>$addon</i> is incompatible. They have version <b>$host_ver</b> while you have version <b>$local_ver</b>.", {
-				{"addon",     content_name},
+				{"addon",     local_item["addon_title"]},
 				{"host_ver",  remote_ver.str()},
 				{"local_ver", local_ver.str()}
 			});
@@ -499,7 +493,7 @@ game_info::ADDON_REQ game_info::check_addon_version_compatibility(const config&
 			r.outcome = NEED_DOWNLOAD;
 
 			r.message = vgettext("Your version of <i>$addon</i> is incompatible. You have version <b>$local_ver</b> while the host has version <b>$host_ver</b>.", {
-				{"addon",     content_name},
+				{"addon",     local_item["addon_title"]},
 				{"host_ver",  remote_ver.str()},
 				{"local_ver", local_ver.str()}
 			});

src/mp_game_settings.cpp

@@ -145,6 +145,7 @@ config mp_game_settings::to_config() const
 mp_game_settings::addon_version_info::addon_version_info(const config & cfg)
 	: version()
 	, min_version()
+	, name(cfg["name"])
 {
 	if (!cfg["version"].empty()) {
 		version = cfg["version"].str();
@@ -161,6 +162,8 @@ void mp_game_settings::addon_version_info::write(config & cfg) const {
 	if (min_version) {
 		cfg["min_version"] = *min_version;
 	}
+
+	cfg["name"]	= name;
 }
 
 void mp_game_settings::update_addon_requirements(const config & cfg) {

src/mp_game_settings.hpp

@@ -72,17 +72,23 @@ struct mp_game_settings
 
 	config options;
 
-	struct addon_version_info {
+	struct addon_version_info
+	{
 		boost::optional<version_info> version;
 		boost::optional<version_info> min_version;
 
+		std::string name;
+
 		explicit addon_version_info(const config &);
 		void write(config &) const;
 	};
 
 	std::map<std::string, addon_version_info> addons; // the key is the addon_id
 
-	// Takes a config with addon metadata (id =, version =, min_version =), formatted similarly to how mp_game_settings is written that is,
-	// and adds this as a requirement, updating the min_version if there was already an entry for this addon_id.
-	void update_addon_requirements(const config & addon_cfg);
+	/**
+	 * Takes a config with addon metadata (id, name, version, min_version) and adds
+	 * it as a requirement for this game. It also updates min_version if there was
+	 * already an entry for this addon_id.
+	 */
+	void update_addon_requirements(const config& addon_cfg);
 };

src/saved_game.cpp

@@ -233,11 +233,14 @@ void saved_game::expand_scenario()
 
 			// Add addon_id information if it exists.
 			if(!scenario["addon_id"].empty() && scenario["require_scenario"].to_bool(false)) {
-				mp_settings_.update_addon_requirements(config {
-					"id", scenario["addon_id"],
-					"version", scenario["addon_version"],
-					"min_version", scenario["addon_min_version"]
-				});
+				config required_scenario;
+
+				required_scenario["id"] = scenario["addon_id"];
+				required_scenario["name"] = scenario["addon_title"];
+				required_scenario["version"] = scenario["addon_version"];
+				required_scenario["min_version"] = scenario["addon_min_version"];
+
+				mp_settings_.update_addon_requirements(required_scenario);
 			}
 
 			update_label();
@@ -282,8 +285,14 @@ void saved_game::load_mod(const std::string& type, const std::string& id)
 		bool require_default = (type == "era");
 
 		if(!cfg["addon_id"].empty() && cfg[require_attr].to_bool(require_default)) {
-			mp_settings_.update_addon_requirements(config{
-				"id", cfg["addon_id"], "version", cfg["addon_version"], "min_version", cfg["addon_min_version"]});
+			config required_mod;
+
+			required_mod["id"] = cfg["addon_id"];
+			required_mod["name"] = cfg["addon_title"];
+			required_mod["version"] = cfg["addon_version"];
+			required_mod["min_version"] = cfg["addon_min_version"];
+
+			mp_settings_.update_addon_requirements(required_mod);
 		}
 
 		// Copy events