Clearer warning message, the old one lacked information and was perhaps misleading (#2927) (#2931)

* change misleading warning message, making it more correct and informative



* Fix compile error. Needed to also build rcl from source.



* explicitely initialize pointer as null, to adhere to best practice



---------


(cherry picked from commit 3767779)

Signed-off-by: Peter Mitrano (AR) <[email protected]>
Co-authored-by: Peter Mitrano (AR) <[email protected]>

Author: mergify[bot]

rclcpp_lifecycle/src/lifecycle_node_interface_impl.cpp

@@ -390,6 +390,7 @@ LifecycleNode::LifecycleNodeInterfaceImpl::change_state(
   constexpr bool publish_update = true;
   State initial_state;
   unsigned int current_state_id;
+  const rcl_lifecycle_transition_t * original_transition{nullptr};
 
   {
     std::lock_guard<std::recursive_mutex> lock(state_machine_mutex_);
@@ -405,6 +406,10 @@ LifecycleNode::LifecycleNodeInterfaceImpl::change_state(
     // keep the initial state to pass to a transition callback
     initial_state = State(state_machine_.current_state);
 
+    original_transition =
+      rcl_lifecycle_get_transition_by_id(state_machine_.current_state, transition_id);
+
+
     if (
       rcl_lifecycle_trigger_transition_by_id(
         &state_machine_, transition_id, publish_update) != RCL_RET_OK)
@@ -455,12 +460,15 @@ LifecycleNode::LifecycleNodeInterfaceImpl::change_state(
   // Update the internal current_state_
   current_state_ = State(state_machine_.current_state);
 
-  // error handling ?!
+  // error handling
   // TODO(karsten1987): iterate over possible ret value
   if (cb_return_code == node_interfaces::LifecycleNodeInterface::CallbackReturn::ERROR) {
-    RCLCPP_WARN(
-      node_logging_interface_->get_logger(),
-      "Error occurred while doing error handling.");
+    if (original_transition) {
+      RCLCPP_WARN(
+        node_logging_interface_->get_logger(),
+        "Callback returned ERROR during the transition: %s", original_transition->label);
+    }
+
 
     auto error_cb_code = execute_callback(current_state_id, initial_state);
     auto error_cb_label = get_label_for_return_code(error_cb_code);