Port point_cloud_transport_plugins to ROS2

[john-maidbot]

Sister PR to ros-perception/point_cloud_transport#1

See there for commentary and reports on progress.

[ahcorde]

I'm getting some errors like this one:

/home/ahcorde/ros2_rolling/src/point_cloud_transport_plugins/draco_point_cloud_transport/src/draco_publisher.cpp: In member function ‘tl::expected<std::unique_ptr<draco::PointCloud>, std::__cxx11::basic_string<char> > draco_point_cloud_transport::DracoPublisher::convertPC2toDraco(const PointCloud2&, const string&, bool, bool) const’:
/home/ahcorde/ros2_rolling/src/point_cloud_transport_plugins/draco_point_cloud_transport/src/draco_publisher.cpp:155:43: error: could not convert ‘tl::make_unexpected<const char (&)[53]>("Invalid data type in PointCloud2 to Draco conversion")’ from ‘tl::unexpected<const char*>’ to ‘tl::expected<std::unique_ptr<draco::PointCloud>, std::__cxx11::basic_string<char> >’
  155 |       default:return cras::make_unexpected("Invalid data type in PointCloud2 to Draco conversion");
      |                      ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |                                           |
      |                                           tl::unexpected<const char*>

[john-maidbot]

Hrmmm, if you don’t mind me asking, what is your setup? (OS version / ROS version / g++ compiler version) This seems like it could be compiler related, as I do not see that error.
I.e. you compiler is interpreting that text as a const char* but mine sees it as a std::string (or ignoring that line for some reason).

We could maybe fix it by explicitly passing an std::string rather than something that is open to interpretation?
E.g.

cras::make_unexpected(std::string("Invalid data type in PointCloud2 to Draco conversion"));

Or we could refactor the behavior to return a nullptr rather than using the expected<> mechanism.

[peci1]

You can also try updating the https://raw.githubusercontent.com/TartanLlama/expected library. There were a few releases since I pulled it into cras_cpp_common.

We could maybe fix it by explicitly passing an std::string rather than something that is open to interpretation? E.g.

cras::make_unexpected(std::string("Invalid data type in PointCloud2 to Draco conversion"));

This would most probably fix it, but it is ugly.

It's weird a compiler for a ROS 2 system would not understand this. I tested this on C++14-only compilers and they work with the library.

[john-maidbot]

You can also try updating the https://raw.githubusercontent.com/TartanLlama/expected library.

I tried this, but the only diff is that they altered the version number. the code seems unaltered according to git.

This would most probably fix it, but it is ugly.

fair point 😅

i will wait to hear back about @ahcorde 's build setup before making any changes.

rn I am building with
Ubuntu 22.04
humble ros2
CMAKE_CXX_STANDARD 17
gcc version 11.3.0 (Ubuntu 11.3.0-1ubuntu1~22.04.1)

and see no build errors/warnings.

[john-maidbot]

@ahcorde i assume you found a way around this issue?