Add parameter default_planning_scene to load planning scene geometry on startup

[pac48]

Description

This PR adds a new parameter to the move_group node that allows users to specify a planning scene file to load on startup. The parameter is a string containing the absolute file path. The parameter can be set with either $(find-pkg-share pkg-wth-planning-file) for XML or ament_index_python.packages.get_package_share_directory in Python to facilitate specifying the path. If the parameter is not specified, the move_group node will behave as it previously did. If there is an error loading the file, the node will exit with a fatal error.

Checklist

• Extend the tutorials / documentation reference
• Create tests, which fail without this PR reference

[sjahr]

I think this is too dangerous because you're not locking the planning scene when writing to it (see

moveit2/moveit_ros/planning/planning_scene_monitor/include/moveit/planning_scene_monitor/planning_scene_monitor.h

Line 170 in 19d4a28

* @warning Most likely you do not want to call this function

).
You can get thread safe access like this:

{
  planning_scene_monitor::LockedPlanningSceneRW ps = planning_display_->getPlanningSceneRW();
  if (ps)
     FANCY MODIFICATIONS
} // End scope to release lock

[github-actions]

This PR is stale because it has been open for 45 days with no activity. Please tag a maintainer for help on completing this PR, or close it if you think it has become obsolete.

[sjahr]

@pac48 Should we close this?

[pac48]

@sjahr We should try to merge this. I think the change to the test should either be deleted or more effort has to be put in to make it not flaky.

[sjahr]

I think it is a useful addition but it could be hardened a bit to make it harder to misuse. Also can you add the PR description as a documentation comment on top of this function call? At the moment there is nothing explaining what this is doing or how it is supposed to be used

[sjahr]

Given that ps is never used, would make sense to revert this change?

[sjahr]

I am a bit concerned about tying this to only the existence of the parameter. How about checking whether or not the parameter is set.

const auto default_planning_scene_file = std::string();
nh->get_parameter_or("default_planning_scene", default_planning_scene_file, std::string());
// Maybe add function to validate the string pattern if it actually representing  path
if(validateFilePath(default_planning_scene_file))
{
...
}