Ament_cmake - recommended way to link a library doesn't work?

edit

I'm trying to pull in the Eigen3 library as a dependency of my library on Dashing (latest patch release, on Ubuntu), but I'm not sure the "most correct" way to do this.

This does not build, but is what I thought was the recommendation:

find_package(Eigen3 REQUIRED)
ament_target_dependencies(sba Eigen3)

It fails with something like:

--- stderr: sparse_bundle_adjustment                                                                               
In file included from /home/dan/ros2_ws/src/sparse_bundle_adjustment/src/sba.cpp:39:0:
/home/dan/ros2_ws/src/sparse_bundle_adjustment/include/sparse_bundle_adjustment/sba.h:48:10: fatal error: Eigen/Core: No such file or directory
 #include <Eigen/Core>
          ^~~~~~~~~~~~
compilation terminated.
make[2]: *** [CMakeFiles/sba.dir/src/sba.cpp.o] Error 1
make[1]: *** [CMakeFiles/sba.dir/all] Error 2
make: *** [all] Error 2

This builds, and is listed as the way to do it up to ROS Crystal, with caveats:

find_package(Eigen3 REQUIRED)
target_link_libraries(sba Eigen3::Eigen)

This builds, is not in the docs, and I know is terrible practice:

find_package(Eigen3 REQUIRED)
target_include_directories(sba PRIVATE ${EIGEN3_INCLUDE_DIRS})
target_compile_definitions(sba PRIVATE ${EIGEN3_DEFINITIONS})

Entire CMakeLists for context:

cmake_minimum_required(VERSION 3.5)
project(sparse_bundle_adjustment)

if(NOT CMAKE_CXX_STANDARD)
  set(CMAKE_CXX_STANDARD 11)
endif()

find_package(ament_cmake REQUIRED)

add_library(sba
  src/sba.cpp src/spa.cpp src/spa2d.cpp src/csparse.cpp src/proj.cpp src/node.cpp src/sba_file_io.cpp)

target_include_directories(sba
  PUBLIC
  $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
  $<INSTALL_INTERFACE:include>)

# this does not build
find_package(Eigen3 REQUIRED)
ament_target_dependencies(sba Eigen3)

## this builds
#find_package(Eigen3 REQUIRED)
#target_link_libraries(sba Eigen3::Eigen)

## this builds
#find_package(Eigen3 REQUIRED)
#target_include_directories(sba PUBLIC ${EIGEN3_INCLUDE_DIRS})
#target_compile_definitions(sba PUBLIC ${EIGEN3_DEFINITIONS})


target_compile_definitions(sba
  PRIVATE SBA_CHOLMOD
  )

ament_export_interfaces(export_sba HAS_LIBRARY_TARGET)
ament_export_dependencies(Eigen3)

target_link_libraries(sba blas lapack cholmod cxsparse)

install(DIRECTORY include/
        DESTINATION include/)

install(
  TARGETS sba
  EXPORT export_sba
  RUNTIME DESTINATION bin
  LIBRARY DESTINATION lib
  INCLUDES DESTINATION include
)
ament_package()