Cannot echo topic as it contains more than one type (but the type naming seems the same)

[TSC21]

Bug report

I am sure that this is not a problem with the ros2cli, since the binding still fails, but it's kinda awkward what's happening in terms of the topic echo part. I am not certain what's causing this, but what I am seeing is, theoretically, the same type name being considered different.

The full description of the problem and reproduction of the steps can be found under eProsima/Fast-DDS#829. To add: the fact that the type name on the agent side was changed on both Publisher and Subscribers using the Fast-RTPS TopicDataType API:

    myType.setName("@(package)/msg/@(topic)");

In order to match the type naming that the ROS2 Pub/Subs expect.

Required Info:

• Operating System:
  • Ubuntu 18.04
• Installation type:
  • Dashing, from binaries
• Version or commit hash:
  • ros2cli 0.7.9-1bionic.20191212.194301
• DDS implementation:
  • rmw_fastrtps
• Client library (if applicable):
  • rclcpp

Expected behavior

I expected the topic to have only data of the same type and ros2 topic echo actually output the data stream.

Actual behavior

eProsima/Fast-DDS#829 (comment):

$ ros2 topic echo /SensorCombined_PubSubTopic 
Cannot echo topic '/SensorCombined_PubSubTopic', as it contains more than one type: [px4_msgs/msg/SensorCombined, px4_msgs/msg/SensorCombined]

Additional information

All the information can be found under eProsima/Fast-DDS#829.

@dirk-thomas thanks in advance for your time and patience.

[thomasgubler]

@tfoote @dirk-thomas FYI this issue is blocking integration of ROS2 Dashing into PX4. We might have missed something in our setup and would be very thankful for your input.

[TSC21]

This was solved in PX4/PX4-Autopilot#13907.