Should support libsdformat in robot_state_publisher

[azeey]

Should extend robot_state_publisher to use libsdformat, parse a subset of SDFormat (KDL-compatible).

Should target:
https://github.com/ros/robot_state_publisher

[EricCousineau-TRI]

Created per convo with @IanTheEngineer.

Some additional things to consider:

• Could be supported by having libsdformat depend on KDL (or whatever intermediate representation robot_state_publisher uses), and emit a structure
• I haven't looked yet at how robot_state_publisher handles multi-dof joint names. We should ensure this is handled here as well.

(Possibly relates #253 in how joint dofs are named.)

\cc @joemasterjohn

[EricCousineau-TRI]

Per f2f with @scpeters, @azeey, @IanTheEngineer:

My suggestion is to make users can "hook" / override URIs. package:// should only be handled by ROS, not by some weird shim in libsdformat. (If there is a shim, it should get overridden.)

[EricCousineau-TRI]

FTR The "weird" shim is the current "addURIPath" API:
https://github.com/osrf/sdformat/blob/sdformat9_9.0.0/include/sdf/SDFImpl.hh#L67-L72

A better mechanism would be to purely something like setFindCallback, but strictly associated with a given URL prefix:
https://github.com/osrf/sdformat/blob/sdformat9_9.0.0/include/sdf/SDFImpl.hh#L74-L79

(Saw this when reviewing gazebosim/sdf_tutorials#14)

[IanTheEngineer]

It seems this task can be accomplished by the steps I've outline in
ros/urdf#34

Namely, a sdformat_parser ROS package that populates the urdf::Model API through urdf::Model::initString()

[EricCousineau-TRI]

@sloretz Would you say this task is now done, given your most recent ROS2 contributions?

[sloretz]

@sloretz Would you say this task is now done, given your most recent ROS2 contributions?

Definitely (linking: https://github.com/ros/sdformat_urdf)

[EricCousineau-TRI]

Sweet! Marking this as resolved.