Diagnose Configuration and Launch Failures

Not every failure is a broken executable.

Configuration can be wrong while code remains fine.

Parameter mismatch

Inspect:

ros2 param list
ros2 param get <node_name> <parameter_name>

Compare running values to the intended parameter file or launch configuration.

Remapping mismatch

Inspect resolved graph names:

ros2 topic list -t
ros2 topic info <topic_name> --verbose

Compare with the launch file's remappings.

Launch file missing

If direct file launch works but package launch cannot discover the file, inspect package installation metadata and rebuild.

Launch starts one process and another exits

Read the launch terminal. Launch reports process start/exit evidence. Then classify whether the failed process had an import, executable-discovery, configuration, or application error.

Parameter-file problems

When using --params-file, distinguish:

• file path not found;
• YAML structure invalid;
• parameter name absent/read-only;
• node starts but value is not what you intended.

Checkpoint

Choose one configuration failure and show how the graph can be wrong even when both Python source files are unchanged.