Implicitly linked libraries ignore INTERFACE_LINK_LIBRARIES

[rotu]

Implicitly linking a library through ament_cmake by importing a package that uses ament_export_libraries will cause that library target's INTERFACE_LINK_LIBRARIES to be ignored.

Say I create a library with

cmake_minimum_required(VERSION 3.5)
project(ProjectA)

add_library(LibA my_library.cpp)
target_link_libraries(LibA PUBLIC systemLib)
# ...
ament_export_libraries(LibA)
ament_package()

Then including this library downstream with:

ament_target_dependencies(LibB LibA)

will cause a link-time error, as systemLib is not recursively linked.
On the other hand, this does cause systemLib to get linked:

find_package(ProjectA REQUIRED)
target_link_libraries(LibB ProjectA::LibA)

It is expected that ament_cmake will respect the standard interface link property.

[rotu]

Possibly useful discussion here https://answers.ros.org/question/331277/ament_cmake-confused-about-ament_export_dependencies-and-ament_export_interfaces/