CMake export a target that is using rosidl_target_interfaces.

[MaximilienNaveau]

Bug report

Required Info:

• Operating System:
  • Ubuntu 18.04 / RT_PREEMPT
• Installation type:
  • ROS eloquent binaries
• Version or commit hash:
  • unknown?
• DDS implementation:
  • unknown?
• Client library (if applicable):
  • rclcpp, rosidl_default_generators

Steps to reproduce issue

CMakeLists.txt

...

find_package(rosidl_default_generators REQUIRED)
rosidl_generate_interfaces(${PROJECT_NAME}_msg_srv "msg/MyMessage.msg")
...
add_library(mylib SHARED my_cpp_file.cpp)
target_include_directories(
  mylib PUBLIC $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
               $<INSTALL_INTERFACE:include>)
rosidl_target_interfaces(mylib ${PROJECT_NAME}_msg_srv "rosidl_typesupport_cpp")
...
# install and export
ament_export_interfaces(export_${PROJECT_NAME} HAS_LIBRARY_TARGET)
install(
  TARGETS mylib
  EXPORT export_${PROJECT_NAME}
  LIBRARY DESTINATION lib
  ARCHIVE DESTINATION lib
  RUNTIME DESTINATION lib/${PROJECT_NAME}
  INCLUDES
  DESTINATION include)

Expected behavior

Successfull build.

Actual behavior

CMake Error in src/CMakeLists.txt:
  Target "my_package" INTERFACE_INCLUDE_DIRECTORIES property
  contains path:

    "<full_path_to>/workspace_ros2/build/my_package/rosidl_generator_cpp"

  which is prefixed in the build directory.

Additional information

I do think the problem comes from here: https://github.com/ros2/rosidl/blob/eloquent/rosidl_cmake/cmake/rosidl_target_interfaces.cmake#L52

This:

target_include_directories(${target} PUBLIC ${include_directories})

should become this:

target_include_directories(${target} PUBLIC $<BUILD_INTERFACE:${include_directories}>)

Or maybe I am not using these tools properly...

[sloretz]

The function rosidl_target_interfaces() is being deprecated in the next release in favor of a new function rosidl_get_typesupport_target(). I don't think that will be backported to ROS Eloquent, but it's very easy to copy what it does - adds two underscores between the generation target name and the type support name.

rosidl/rosidl_cmake/cmake/rosidl_get_typesupport_target.cmake

Lines 27 to 40 in e76ed13

	function(rosidl_get_typesupport_target var generate_interfaces_target typesupport_name)
	if(NOT TARGET ${generate_interfaces_target})
	message(FATAL_ERROR
	"${generate_interfaces_target} is not a CMake target. Maybe rosidl_generate_interfaces was given a different target name?")
	endif()
	set(output_target "${generate_interfaces_target}__${typesupport_name}")
	if(NOT TARGET ${output_target})
	message(FATAL_ERROR "${output_target} is not a CMake target - maybe the typesupport '${typesupport_name}' doesn't exist?")
	endif()
	set("${var}" "${output_target}" PARENT_SCOPE)
	endfunction()

A solution might look like this:

rosidl_generate_interfaces(${PROJECT_NAME}_msg_srv "msg/MyMessage.msg")
...
add_library(mylib SHARED my_cpp_file.cpp)
...
target_link_libraries(mylib PUBLIC "${PROJECT_NAME}_msg_srv__rosidl_typesupport_cpp")

ros2/ros2_documentation#1798

I'll close this since ROS Eloquent is EOL and the problematic function is already deprecated in future ROS releases

[MaximilienNaveau]

Thank you very much for the answer!