4 files changed, 50 insertions, 15 deletions

diff --git a/modules/multiplayer/multiplayer_spawner.cpp b/modules/multiplayer/multiplayer_spawner.cpp
index 7ed69a84d0..0aa54b69f9 100644
--- a/modules/multiplayer/multiplayer_spawner.cpp
+++ b/modules/multiplayer/multiplayer_spawner.cpp
@@ -199,10 +199,6 @@ void MultiplayerSpawner::_notification(int p_what) {
 				Node *node = Object::cast_to<Node>(ObjectDB::get_instance(E.key));
 				ERR_CONTINUE(!node);
 				node->disconnect(SceneStringNames::get_singleton()->tree_exiting, callable_mp(this, &MultiplayerSpawner::_node_exit));
-				// This is unlikely, but might still crash the engine.
-				if (node->is_connected(SceneStringNames::get_singleton()->ready, callable_mp(this, &MultiplayerSpawner::_node_ready))) {
-					node->disconnect(SceneStringNames::get_singleton()->ready, callable_mp(this, &MultiplayerSpawner::_node_ready));
-				}
 				get_multiplayer()->object_configuration_remove(node, this);
 			}
 			tracked_nodes.clear();
@@ -244,11 +240,11 @@ void MultiplayerSpawner::_track(Node *p_node, const Variant &p_argument, int p_s
 	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_ONE_SHOT);
-		p_node->connect(SceneStringNames::get_singleton()->ready, callable_mp(this, &MultiplayerSpawner::_node_ready).bind(p_node->get_instance_id()), CONNECT_ONE_SHOT);
+		_spawn_notify(p_node->get_instance_id());
 	}
 }
 
-void MultiplayerSpawner::_node_ready(ObjectID p_id) {
+void MultiplayerSpawner::_spawn_notify(ObjectID p_id) {
 	get_multiplayer()->object_configuration_add(ObjectDB::get_instance(p_id), this);
 }
 
diff --git a/modules/multiplayer/multiplayer_spawner.h b/modules/multiplayer/multiplayer_spawner.h
index 8d401a6818..8a54140e32 100644
--- a/modules/multiplayer/multiplayer_spawner.h
+++ b/modules/multiplayer/multiplayer_spawner.h
@@ -77,7 +77,7 @@ private:
 	void _track(Node *p_node, const Variant &p_argument, int p_scene_id = INVALID_ID);
 	void _node_added(Node *p_node);
 	void _node_exit(ObjectID p_id);
-	void _node_ready(ObjectID p_id);
+	void _spawn_notify(ObjectID p_id);
 
 	Vector<String> _get_spawnable_scenes() const;
 	void _set_spawnable_scenes(const Vector<String> &p_scenes);
diff --git a/modules/multiplayer/scene_replication_interface.cpp b/modules/multiplayer/scene_replication_interface.cpp
index e1b7b0c346..233ff76c7d 100644
--- a/modules/multiplayer/scene_replication_interface.cpp
+++ b/modules/multiplayer/scene_replication_interface.cpp
@@ -125,6 +125,20 @@ void SceneReplicationInterface::on_reset() {
 }
 
 void SceneReplicationInterface::on_network_process() {
+	// Prevent endless stalling in case of unforseen spawn errors.
+	if (spawn_queue.size()) {
+		ERR_PRINT("An error happened during last spawn, this usually means the 'ready' signal was not emitted by the spawned node.");
+		for (const ObjectID &oid : spawn_queue) {
+			Node *node = get_id_as<Node>(oid);
+			ERR_CONTINUE(!node);
+			if (node->is_connected(SceneStringNames::get_singleton()->ready, callable_mp(this, &SceneReplicationInterface::_node_ready))) {
+				node->disconnect(SceneStringNames::get_singleton()->ready, callable_mp(this, &SceneReplicationInterface::_node_ready));
+			}
+		}
+		spawn_queue.clear();
+	}
+
+	// Process timed syncs.
 	uint64_t msec = OS::get_singleton()->get_ticks_msec();
 	for (KeyValue<int, PeerInfo> &E : peers_info) {
 		const HashSet<ObjectID> to_sync = E.value.sync_nodes;
@@ -144,17 +158,39 @@ Error SceneReplicationInterface::on_spawn(Object *p_obj, Variant p_config) {
 	// Track node.
 	const ObjectID oid = node->get_instance_id();
 	TrackedNode &tobj = _track(oid);
+
+	// Spawn state needs to be callected after "ready", but the spawn order follows "enter_tree".
 	ERR_FAIL_COND_V(tobj.spawner != ObjectID(), ERR_ALREADY_IN_USE);
 	tobj.spawner = spawner->get_instance_id();
-	spawned_nodes.insert(oid);
+	spawn_queue.insert(oid);
+	node->connect(SceneStringNames::get_singleton()->ready, callable_mp(this, &SceneReplicationInterface::_node_ready).bind(oid), Node::CONNECT_ONE_SHOT);
+	return OK;
+}
+
+void SceneReplicationInterface::_node_ready(const ObjectID &p_oid) {
+	ERR_FAIL_COND(!spawn_queue.has(p_oid)); // Bug.
 
-	if (multiplayer->has_multiplayer_peer() && spawner->is_multiplayer_authority()) {
-		if (tobj.net_id == 0) {
-			tobj.net_id = ++last_net_id;
+	// If we are a nested spawn, we need to wait until the parent is ready.
+	if (p_oid != *(spawn_queue.begin())) {
+		return;
+	}
+
+	for (const ObjectID &oid : spawn_queue) {
+		ERR_CONTINUE(!tracked_nodes.has(oid));
+
+		TrackedNode &tobj = tracked_nodes[oid];
+		MultiplayerSpawner *spawner = get_id_as<MultiplayerSpawner>(tobj.spawner);
+		ERR_CONTINUE(!spawner);
+
+		spawned_nodes.insert(oid);
+		if (multiplayer->has_multiplayer_peer() && spawner->is_multiplayer_authority()) {
+			if (tobj.net_id == 0) {
+				tobj.net_id = ++last_net_id;
+			}
+			_update_spawn_visibility(0, oid);
 		}
-		_update_spawn_visibility(0, oid);
 	}
-	return OK;
+	spawn_queue.clear();
 }
 
 Error SceneReplicationInterface::on_despawn(Object *p_obj, Variant p_config) {
diff --git a/modules/multiplayer/scene_replication_interface.h b/modules/multiplayer/scene_replication_interface.h
index a5e610cff6..cf45db2138 100644
--- a/modules/multiplayer/scene_replication_interface.h
+++ b/modules/multiplayer/scene_replication_interface.h
@@ -51,7 +51,6 @@ private:
 
 		bool operator==(const ObjectID &p_other) { return id == p_other; }
 
-		_FORCE_INLINE_ MultiplayerSpawner *get_spawner() const { return spawner.is_valid() ? Object::cast_to<MultiplayerSpawner>(ObjectDB::get_instance(spawner)) : nullptr; }
 		TrackedNode() {}
 		TrackedNode(const ObjectID &p_id) { id = p_id; }
 		TrackedNode(const ObjectID &p_id, uint32_t p_net_id) {
@@ -75,7 +74,10 @@ private:
 	HashSet<ObjectID> spawned_nodes;
 	HashSet<ObjectID> sync_nodes;
 
-	// Pending spawn information.
+	// Pending local spawn information (handles spawning nested nodes during ready).
+	HashSet<ObjectID> spawn_queue;
+
+	// Pending remote spawn information.
 	ObjectID pending_spawn;
 	int pending_spawn_remote = 0;
 	const uint8_t *pending_buffer = nullptr;
@@ -89,6 +91,7 @@ private:
 
 	TrackedNode &_track(const ObjectID &p_id);
 	void _untrack(const ObjectID &p_id);
+	void _node_ready(const ObjectID &p_oid);
 
 	void _send_sync(int p_peer, const HashSet<ObjectID> p_synchronizers, uint16_t p_sync_net_time, uint64_t p_msec);
 	Error _make_spawn_packet(Node *p_node, MultiplayerSpawner *p_spawner, int &r_len);