rosbridge can’t subscribe to ROS 2 action topic `/navigate_to_pose/_action/feedback`

[AdarshKaran]

Description

• Library Version: rosbridge suite v2.3.0 (binaries installed using apt: ros-rolling-rosbridge-msgs ros-rolling-rosbridge-library ros-rolling-rosbridge-server ros-rolling-rosbridge-suite), roslibjs npm 1.4.1 (we understand this version doesn't support Actions and only the v2 version does, but the issue wasn't with roslib, added only for context), Nav2 build from src (Rolling)
• ROS Version: ROS 2 Rolling (Debian)
• Platform / OS: Ubuntu 24.04

Subscribing to the ROS 2 action feedback topic /navigate_to_pose/_action/feedback (type nav2_msgs/action/NavigateToPose_FeedbackMessage) from rosbridge throws the error

[rosbridge_websocket-1] [ERROR] [1756883713.567298692] [rosbridge_websocket]: [Client fc2f145c-2bf9-47e4-82dc-1c08d08975e5] [id: subscribe:/navigate_to_pose/_action/feedback:22] subscribe: Unable to import msg class NavigateToPose_FeedbackMessage from package nav2_msgs. Caused by module 'nav2_msgs.msg' has no attribute 'NavigateToPose_FeedbackMessage'

since rosbridge tries to import from nav2_msgs.msg instead of nav2_msgs.action.

This seems like rosbridge’s type loader is looking for nav2_msgs.msg.NavigateToPose_FeedbackMessage, but in ROS 2 these wrapper types used by these actions are under nav2_msgs.action.

RViz nav2 panel (here https://github.com/ros-navigation/navigation2/blob/main/nav2_rviz_plugins/src/nav2_panel.cpp) does a similar thing. rclcpp subscribes to the action’s feedback topic using the generated C++ type nav2_msgs::action::NavigateToPose::Impl::FeedbackMessage.

Rosbridge Action API works fine in our testing if the goal is sent via rosbridge. Meaning, if we don't use our pkg to send action goals. The problem here is subscribe to the hidden wrapper topic when goals are sent by another node.

@padhupradheep and I have been working on a GUI tool that uses WebSockets for communicating with ROS 2. Hence we decided to use rosbridge suite with roslibjs .We trigger navigation via our package neo_waypoint_follower by calling the /start_waypoint_loop service (std_srvs/srv/Trigger, implemented by the waypoint_looper node);

We are not sending the action goal via rosbridge, so rosbridge’s Action API callbacks (which are tied to a client-side goal handle) cannot be used in our setup. Instead, we try to subscribe directly to /navigate_to_pose/_action/feedback, and hence the issue.

As a workaround, we could have the neo_waypoint_follower pkg node republish a feedback topics for the specific fields our GUI needs -estimated_time_remaining, distance_remaining and navigation_time and have the GUI subscribe to that. However, this is redundant because Nav2 already publishes these via the /navigate_to_pose/_action/feedback topic.

Looking at rosbridge_library/internal/ros_loader.py, the message loader for subscribe paths might be importing from pkg.msg. For types provided as pkg/action/Name_* it could instead import from pkg.action.

This would bring subscribing capability close to what was done in RViz’s Nav2 panel that subscribes to nav2_msgs::action::NavigateToPose::Impl::FeedbackMessage.

Please advise on the correct path forward. Is this a rosbridge limitation or bug in the subscribe path for ROS 2 action wrapper message types, or are we misusing the API?
Happy to provide additional logs or context. Thanks in advance.

---

Steps To Reproduce

1. With a navigate_to_pose task active, we verified the hidden feedback topics exist:

   ros2 topic list -a | grep navigate_to_pose
   # includes  /navigate_to_pose/_action/feedback
   ros2 topic info -t /navigate_to_pose/_action/feedback
   # Type: nav2_msgs/action/NavigateToPose_FeedbackMessage
   

2. Connecting a roslibjs client and subscribe:

   new ROSLIB.Topic({
     ros,
     name: '/navigate_to_pose/_action/feedback',
     messageType: 'nav2_msgs/action/NavigateToPose_FeedbackMessage',
   }).subscribe(msg => {
     const fb = msg.feedback || msg;
     const secs = t => (t?.sec ?? 0) + (t?.nanosec ?? 0) / 1e9;
     // consume fb.navigation_time, fb.estimated_time_remaining, fb.distance_remaining …
   });
   

   This is what causes the following error.

3. In our launch file we do:

   IncludeLaunchDescription(
           XMLLaunchDescriptionSource(
               os.path.join(get_package_share_directory('rosbridge_server'), 'launch', 'rosbridge_websocket_launch.xml')
               )
           )
   

---

Expected Behavior

Rosbridge should successfully import the wrapper type from the *.action module and deliver messages to the client, identical to native rclcpp/rclpy subscribers and RViz.

---

Actual Behavior

the error message

[rosbridge_websocket-1] [ERROR] [1756883713.567298692] [rosbridge_websocket]: [Client fc2f145c-2bf9-47e4-82dc-1c08d08975e5] [id: subscribe:/navigate_to_pose/_action/feedback:22] subscribe: Unable to import msg class NavigateToPose_FeedbackMessage from package nav2_msgs. Caused by module 'nav2_msgs.msg' has no attribute 'NavigateToPose_FeedbackMessage'

Type import fails because rosbridge attempts to import from the *.msg module:

nav2_msgs.msg.NavigateToPose_FeedbackMessage  # (does not exist)

[bjsowa]

Type import fails because rosbridge attempts to import from the *.msg module:

nav2_msgs.msg.NavigateToPose_FeedbackMessage  # (does not exist)

The problem is: nav2_msgs.action.NavigateToPose_FeedbackMessage also does not exist. The actual message class is:

nav2_msgs.action._navigate_through_poses.NavigateThroughPoses_FeedbackMessage

or

nav2_msgs.action._navigate_through_poses.NavigateThroughPoses.Impl.FeedbackMessage

I looked at how ros2 topic commands import the correct message class and they use rosidl_runtime_py package which has a special case for action feedback messages.

Maybe we could add similar exception, or, even better, replace ros_loader with functions from rosidl_runtime_py