3 files changed, 87 insertions, 0 deletions

diff --git a/base/commandLine.cpp b/base/commandLine.cpp
index 74a5982f32..5c823b2425 100644
--- a/base/commandLine.cpp
+++ b/base/commandLine.cpp
@@ -769,6 +769,7 @@ static Common::Error listSaves(const Common::String &target) {
 		const Plugin *plugin = nullptr;
 		PlainGameDescriptor game;
 		if (domain) {
+			EngineMan.upgradeTargetIfNecessary(target);
 			game = EngineMan.findTarget(target, &plugin);
 		} else {
 			game = EngineMan.findGame(target, &plugin);
diff --git a/base/main.cpp b/base/main.cpp
index 45c8e393b7..85fdbb2986 100644
--- a/base/main.cpp
+++ b/base/main.cpp
@@ -545,6 +545,8 @@ extern "C" int scummvm_main(int argc, const char * const argv[]) {
 	while (0 != ConfMan.getActiveDomain()) {
 		saveLastLaunchedTarget(ConfMan.getActiveDomainName());
 
+		EngineMan.upgradeTargetIfNecessary(ConfMan.getActiveDomainName());
+
 		// Try to find a plugin which feels responsible for the specified game.
 		const Plugin *plugin = detectPlugin();
 		if (plugin) {
diff --git a/base/plugins.cpp b/base/plugins.cpp
index a64dbdd65c..ac98de4d15 100644
--- a/base/plugins.cpp
+++ b/base/plugins.cpp
@@ -675,6 +675,90 @@ PlainGameDescriptor EngineManager::findTarget(const Common::String &target, cons
 	return desc;
 }
 
+void EngineManager::upgradeTargetIfNecessary(const Common::String &target) const {
+	Common::ConfigManager::Domain *domain = ConfMan.getDomain(target);
+	assert(domain);
+
+	if (!domain->contains("engineid")) {
+		upgradeTargetForEngineId(target);
+	}
+}
+
+void EngineManager::upgradeTargetForEngineId(const Common::String &target) const {
+	Common::ConfigManager::Domain *domain = ConfMan.getDomain(target);
+	assert(domain);
+
+	debug("Target '%s' lacks an engine ID, upgrading...", target.c_str());
+
+	Common::String oldGameId = domain->getVal("gameid");
+	Common::String path = domain->getVal("path");
+
+	// At this point the game ID and game path must be known
+	if (oldGameId.empty()) {
+		warning("The game ID is required to upgrade target '%s'", target.c_str());
+		return;
+	}
+	if (path.empty()) {
+		warning("The game path is required to upgrade target '%s'", target.c_str());
+		return;
+	}
+
+	// Game descriptor for the upgraded target
+	Common::String engineId;
+	Common::String newGameId;
+
+	// First, try to update entries for engines that previously used the "single id" system
+	// Search for an engine whose ID is the game ID
+	const Plugin *plugin = findPlugin(oldGameId);
+	if (plugin) {
+		// Run detection on the game path
+		Common::FSNode dir(path);
+		Common::FSList files;
+		if (!dir.getChildren(files, Common::FSNode::kListAll)) {
+			warning("Failed to access path '%s' when upgrading target '%s'", path.c_str(), target.c_str());
+			return;
+		}
+
+		// Take the first detection entry
+		const MetaEngine &metaEngine = plugin->get<MetaEngine>();
+		DetectedGames candidates = metaEngine.detectGames(files);
+		if (candidates.empty()) {
+			warning("No games supported by the engine '%s' were found in path '%s' when upgrading target '%s'",
+			        metaEngine.getEngineId(), path.c_str(), target.c_str());
+			return;
+		}
+
+		engineId = candidates[0].engineId;
+		newGameId = candidates[0].gameId;
+	}
+
+	// Next, try to find an engine with the game ID in its supported games list
+	if (engineId.empty()) {
+		PlainGameDescriptor pgd = findGame(oldGameId, &plugin);
+		if (plugin) {
+			engineId = plugin->get<MetaEngine>().getEngineId();
+			newGameId = pgd.gameId;
+		}
+	}
+
+	if (engineId.empty() || newGameId.empty()) {
+		warning("No matching engine was found when upgrading target '%s'", target.c_str());
+		return;
+	}
+
+	domain->setVal("engineid", engineId);
+	domain->setVal("gameid", newGameId);
+
+	// Save a backup of the pre-upgrade gameId to the config file
+	if (newGameId != oldGameId) {
+		domain->setVal("oldgameid", oldGameId);
+	}
+
+	debug("Upgrade complete (engine ID '%s', game ID '%s')", engineId.c_str(), newGameId.c_str());
+
+	ConfMan.flushToDisk();
+}
+
 // Music plugins
 
 #include "audio/musicplugin.h"