Context: Working on a pure cmake package (mrpt/package.xml), which can be built standalone, in ROS 1 and in ROS 2. Building in ROS 1/2 with colcon correctly compiles the pure C++ libraries into .so files and their Python3 wrappers (based on pybind11), which are installed via colcon under:

install/mrpt2/lib/python3
install/mrpt2/lib/python3/dist-packages
install/mrpt2/lib/python3/dist-packages/pymrpt.so

The problem: Sourcing . install/setup.bash does NOT populate PYTHONPATH with install/<PKG>/lib/python3/dist-packages/ as would be needed.

What should be added to package.xml or CMakeLists.txt to make colcon to realize there is a Python library out there? Solutions that would work in general with colcon and catkin (for those still using it in ROS 1) would be great! :-)

The current method already generates the python libraries in the correct place when building ROS .deb packages, the unique remaining issue is adding PYTHONPATH when in local builds.