[MP] Add warnings to spawner and synchronizer.

MultiplayerSpawner:
- When spawn_path is invalid.
- When the auto spawn list is empty and _spawn_custom is not overridden.
  Note: We remove the warning for placeholder scripts since there's no
  way of knowing if they have a certain method.

MultiplayerSynchronizer:
- When root_path is invalid.

1 files changed, 10 insertions, 0 deletions

diff --git a/modules/multiplayer/multiplayer_synchronizer.cpp b/modules/multiplayer/multiplayer_synchronizer.cpp
index eee1495c14..01ecd1a7de 100644
--- a/modules/multiplayer/multiplayer_synchronizer.cpp
+++ b/modules/multiplayer/multiplayer_synchronizer.cpp
@@ -94,6 +94,16 @@ void MultiplayerSynchronizer::_update_process() {
 	}
 }
 
+TypedArray<String> MultiplayerSynchronizer::get_configuration_warnings() const {
+	TypedArray<String> 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());