Bug report

Required Info:

• Operating System:
  • Ubuntu 24.04.3 LTS
• Computer:
  • AMD Ryzen 5 3500U
• ROS2 Version:
  • Jazzy binaries
• Version or commit hash:
  • ros-jazzy-navigation2 1.3.10-1noble.20251108.013534
• DDS implementation:
  • Tested with FastDDS and CycloneDDS

Steps to reproduce issue

Configure both the local_costmap and global_costmap with a scan topic name that does not start with a leading slash (/) in a params file:

local_costmap:
  local_costmap:
    ros__parameters:
      voxel_layer:
        observation_sources: scan
        scan:
          topic: prefix/scan  # <--- Topic name without leading slash

global_costmap:
  global_costmap:
    ros__parameters:
      obstacle_layer:
        observation_sources: scan
        scan:
          topic: prefix/scan  # <--- Topic name without leading slash

Expected behavior

Both local_costmap and global_costmap should successfully subscribe to the configured scan source, as the topic name is a valid relative topic name in ROS 2.

Actual behavior

The local_costmap and global_costmap observation layers start without any subscription to the configured scan source and without emitting any warning or error regarding the failure.

• The global_costmap generates a costmap based only on the static map (from amcl).
• The local_costmap generates an empty costmap.

Reproduction instructions

For now, the issue is resolved by adding a leading slash (/) in front of the scan topic name in the params file (e.g., changing prefix/scan to /prefix/scan).

Additional information

This suggests an inconsistent approach in the scan topic name parsing and resolution within the Nav2 stack:

• The local_costmap and global_costmap observation layers fail silently when the scan topic lacks a leading slash.
• Conversely, other core Nav2 components, such as amcl and the collision_monitor, appear to handle the same topic naming convention (relative names without a leading slash) correctly, highlighting a functional divergence in how scan topic names are resolved across the Nav2 package.