Revision history [back]

I suggest do always install dependencies via apt, if there is not a very specific reason to build from source. Thus, install the dependency ros-melodic-pcl-conversions (as this is what you want to include) via apt (any dependencies of that will automatically be installed as well, another advantage vs. from source builds) and you should be good to go.

perception_pcl is only the repository, that contains the packages pcl_conversions, pcl_ros and the perception_pcl metapackage. You can install any package alone (besides dependencies, obviously) via apt. But if you want to build from source, you obviously need to fetch the full repo.