5 files changed, 44 insertions, 9 deletions

diff --git a/modules/multiplayer/multiplayer_spawner.cpp b/modules/multiplayer/multiplayer_spawner.cpp
index e8f3aecc69..9d28feef09 100644
--- a/modules/multiplayer/multiplayer_spawner.cpp
+++ b/modules/multiplayer/multiplayer_spawner.cpp
@@ -86,23 +86,41 @@ void MultiplayerSpawner::_get_property_list(List<PropertyInfo> *p_list) const {
 	}
 }
 #endif
+
+PackedStringArray MultiplayerSpawner::get_configuration_warnings() const {
+	PackedStringArray warnings = Node::get_configuration_warnings();
+
+	if (spawn_path.is_empty() || !has_node(spawn_path)) {
+		warnings.push_back(RTR("A valid NodePath must be set in the \"Spawn Path\" property in order for MultiplayerSpawner to be able to spawn Nodes."));
+	}
+	bool has_scenes = get_spawnable_scene_count() > 0;
+	// Can't check if method is overriden in placeholder scripts.
+	bool has_placeholder_script = get_script_instance() && get_script_instance()->is_placeholder();
+	if (!has_scenes && !GDVIRTUAL_IS_OVERRIDDEN(_spawn_custom) && !has_placeholder_script) {
+		warnings.push_back(RTR("A list of PackedScenes must be set in the \"Auto Spawn List\" property in order for MultiplayerSpawner to automatically spawn them remotely when added as child of \"spawn_path\"."));
+		warnings.push_back(RTR("Alternatively, a Script implementing the function \"_spawn_custom\" must be set for this MultiplayerSpawner, and \"spawn\" must be called explicitly in code."));
+	}
+	return warnings;
+}
+
 void MultiplayerSpawner::add_spawnable_scene(const String &p_path) {
 	SpawnableScene sc;
 	sc.path = p_path;
 	if (Engine::get_singleton()->is_editor_hint()) {
 		ERR_FAIL_COND(!FileAccess::exists(p_path));
-	} else {
-		sc.cache = ResourceLoader::load(p_path);
-		ERR_FAIL_COND_MSG(sc.cache.is_null(), "Invalid spawnable scene: " + p_path);
 	}
 	spawnable_scenes.push_back(sc);
 }
+
 int MultiplayerSpawner::get_spawnable_scene_count() const {
 	return spawnable_scenes.size();
 }
+
 String MultiplayerSpawner::get_spawnable_scene(int p_idx) const {
+	ERR_FAIL_INDEX_V(p_idx, (int)spawnable_scenes.size(), "");
 	return spawnable_scenes[p_idx].path;
 }
+
 void MultiplayerSpawner::clear_spawnable_scenes() {
 	spawnable_scenes.clear();
 }
@@ -230,8 +248,8 @@ void MultiplayerSpawner::_track(Node *p_node, const Variant &p_argument, int p_s
 	ObjectID oid = p_node->get_instance_id();
 	if (!tracked_nodes.has(oid)) {
 		tracked_nodes[oid] = SpawnInfo(p_argument.duplicate(true), p_scene_id);
-		p_node->connect(SceneStringNames::get_singleton()->tree_exiting, callable_mp(this, &MultiplayerSpawner::_node_exit).bind(p_node->get_instance_id()), CONNECT_ONESHOT);
-		p_node->connect(SceneStringNames::get_singleton()->ready, callable_mp(this, &MultiplayerSpawner::_node_ready).bind(p_node->get_instance_id()), CONNECT_ONESHOT);
+		p_node->connect(SceneStringNames::get_singleton()->tree_exiting, callable_mp(this, &MultiplayerSpawner::_node_exit).bind(p_node->get_instance_id()), CONNECT_ONE_SHOT);
+		p_node->connect(SceneStringNames::get_singleton()->ready, callable_mp(this, &MultiplayerSpawner::_node_ready).bind(p_node->get_instance_id()), CONNECT_ONE_SHOT);
 	}
 }
 
@@ -270,9 +288,12 @@ const Variant MultiplayerSpawner::get_spawn_argument(const ObjectID &p_id) const
 Node *MultiplayerSpawner::instantiate_scene(int p_id) {
 	ERR_FAIL_COND_V_MSG(spawn_limit && spawn_limit <= tracked_nodes.size(), nullptr, "Spawn limit reached!");
 	ERR_FAIL_UNSIGNED_INDEX_V((uint32_t)p_id, spawnable_scenes.size(), nullptr);
-	Ref<PackedScene> scene = spawnable_scenes[p_id].cache;
-	ERR_FAIL_COND_V(scene.is_null(), nullptr);
-	return scene->instantiate();
+	SpawnableScene &sc = spawnable_scenes[p_id];
+	if (sc.cache.is_null()) {
+		sc.cache = ResourceLoader::load(sc.path);
+	}
+	ERR_FAIL_COND_V_MSG(sc.cache.is_null(), nullptr, "Invalid spawnable scene: " + sc.path);
+	return sc.cache->instantiate();
 }
 
 Node *MultiplayerSpawner::instantiate_custom(const Variant &p_data) {
diff --git a/modules/multiplayer/multiplayer_spawner.h b/modules/multiplayer/multiplayer_spawner.h
index fc3befc2d4..587c99efd1 100644
--- a/modules/multiplayer/multiplayer_spawner.h
+++ b/modules/multiplayer/multiplayer_spawner.h
@@ -91,6 +91,8 @@ protected:
 	void _get_property_list(List<PropertyInfo> *p_list) const;
 #endif
 public:
+	PackedStringArray get_configuration_warnings() const override;
+
 	Node *get_spawn_node() const {
 		return spawn_node.is_valid() ? Object::cast_to<Node>(ObjectDB::get_instance(spawn_node)) : nullptr;
 	}
diff --git a/modules/multiplayer/multiplayer_synchronizer.cpp b/modules/multiplayer/multiplayer_synchronizer.cpp
index eee1495c14..2c3ebccaeb 100644
--- a/modules/multiplayer/multiplayer_synchronizer.cpp
+++ b/modules/multiplayer/multiplayer_synchronizer.cpp
@@ -94,6 +94,16 @@ void MultiplayerSynchronizer::_update_process() {
 	}
 }
 
+PackedStringArray MultiplayerSynchronizer::get_configuration_warnings() const {
+	PackedStringArray warnings = Node::get_configuration_warnings();
+
+	if (root_path.is_empty() || !has_node(root_path)) {
+		warnings.push_back(RTR("A valid NodePath must be set in the \"Root Path\" property in order for MultiplayerSynchronizer to be able to synchronize properties."));
+	}
+
+	return warnings;
+}
+
 Error MultiplayerSynchronizer::get_state(const List<NodePath> &p_properties, Object *p_obj, Vector<Variant> &r_variant, Vector<const Variant *> &r_variant_ptrs) {
 	ERR_FAIL_COND_V(!p_obj, ERR_INVALID_PARAMETER);
 	r_variant.resize(p_properties.size());
diff --git a/modules/multiplayer/multiplayer_synchronizer.h b/modules/multiplayer/multiplayer_synchronizer.h
index e84d41db86..f10a95a1d4 100644
--- a/modules/multiplayer/multiplayer_synchronizer.h
+++ b/modules/multiplayer/multiplayer_synchronizer.h
@@ -66,6 +66,8 @@ public:
 	static Error get_state(const List<NodePath> &p_properties, Object *p_obj, Vector<Variant> &r_variant, Vector<const Variant *> &r_variant_ptrs);
 	static Error set_state(const List<NodePath> &p_properties, Object *p_obj, const Vector<Variant> &p_state);
 
+	PackedStringArray get_configuration_warnings() const override;
+
 	void set_replication_interval(double p_interval);
 	double get_replication_interval() const;
 	uint64_t get_replication_interval_msec() const;
diff --git a/modules/multiplayer/scene_replication_state.cpp b/modules/multiplayer/scene_replication_state.cpp
index 25442bb7fa..fbcf0acadb 100644
--- a/modules/multiplayer/scene_replication_state.cpp
+++ b/modules/multiplayer/scene_replication_state.cpp
@@ -39,7 +39,7 @@ SceneReplicationState::TrackedNode &SceneReplicationState::_track(const ObjectID
 	if (!tracked_nodes.has(p_id)) {
 		tracked_nodes[p_id] = TrackedNode(p_id);
 		Node *node = Object::cast_to<Node>(ObjectDB::get_instance(p_id));
-		node->connect(SceneStringNames::get_singleton()->tree_exited, callable_mp(this, &SceneReplicationState::_untrack).bind(p_id), Node::CONNECT_ONESHOT);
+		node->connect(SceneStringNames::get_singleton()->tree_exited, callable_mp(this, &SceneReplicationState::_untrack).bind(p_id), Node::CONNECT_ONE_SHOT);
 	}
 	return tracked_nodes[p_id];
 }