Bug report

Required Info:

• Operating System:
  • Ubuntu 20.04, Foxy
• Installation type:
  • From debians
• Version or commit hash:
  • rclcpp 2.0.0
• DDS implementation:
  • Fast-RTPS
• Client library (if applicable):
  • rclcpp

Steps to reproduce issue

I created a full test node here: https://github.com/mikeferguson/ros2_bugs/blob/master/rclcpp_issues/src/count_subscriber_issue.cpp

If you run the node without remapping:

ros2 run rclcpp_issues count_subscriber_issue 

and then echo it:

$ros2 topic echo test
linear:
  x: 42.0
  y: 0.0
  z: 0.0
angular:
  x: 0.0
  y: 0.0
  z: 0.0
---

You get the expected output:

$ros2 run rclcpp_issues count_subscriber_issue
[INFO] [1591928821.734257323] [count_subscriber_issue]: Num of subscribers: 0
[INFO] [1591928822.734171864] [count_subscriber_issue]: Num of subscribers: 0
[INFO] [1591928831.734110847] [count_subscriber_issue]: Num of subscribers: 1
[INFO] [1591928832.734076414] [count_subscriber_issue]: Num of subscribers: 1
[INFO] [1591928833.734027599] [count_subscriber_issue]: Num of subscribers: 1

However, if you remap and then echo the "remapped_test" topic:

ros2 run rclcpp_issues count_subscriber_issue --ros-args -r test:=remapped_test

The subscriber will still subscribe properly and echo the data, but the num of subscribers remains 0 forever.

Expected behavior

I would expect that the count would still be 1 even when remapped. In theory you'd want to define a string that is your "default topic name" and use that same string for create_publisher and count_subscribers and remapping would happen seamlessly under the hood.

Actual behavior

Things don't work with remapping.