Fixed missing grid_map_core include dir in installed cmake config

[matlabbe]

When including grid_map_core (latest version or jazzy) in a cmake project like this:

find_package(grid_map_core)

we get error like this:

<command-line>: fatal error: grid_map_core/eigen_plugins/FunctorsPlugin.hpp: No such file or directory
compilation terminated.

It is because the include directory of that file is not propagated downstream. In Jazzy install directory, we see:

$ ls /opt/ros/jazzy/share/grid_map_core/cmake
ament_cmake_export_dependencies-extras.cmake  grid_map_core-extras.cmake
ament_cmake_export_targets-extras.cmake       grid_map_coreConfig-version.cmake
export_grid_map_coreExport-none.cmake         grid_map_coreConfig.cmake
export_grid_map_coreExport.cmake

And the header file above is added though ADD_DEFINITIONS to downstream projects (grid_map_core-extras.cmake):

set(EIGEN_FUNCTORS_PLUGIN_PATH "grid_map_core/eigen_plugins/FunctorsPlugin.hpp")
if(EIGEN_FUNCTORS_PLUGIN)
  if(NOT EIGEN_FUNCTORS_PLUGIN STREQUAL EIGEN_FUNCTORS_PLUGIN_PATH)
    message(FATAL_ERROR "EIGEN_FUNCTORS_PLUGIN already defined")
  endif()
else()
  add_definitions(-DEIGEN_FUNCTORS_PLUGIN=\"${EIGEN_FUNCTORS_PLUGIN_PATH}\")
endif()

set(EIGEN_DENSEBASE_PLUGIN_PATH "grid_map_core/eigen_plugins/DenseBasePlugin.hpp")
if(EIGEN_DENSEBASE_PLUGIN)
  if(NOT EIGEN_DENSEBASE_PLUGIN STREQUAL EIGEN_DENSEBASE_PLUGIN_PATH)
    message(FATAL_ERROR "EIGEN_DENSEBASE_PLUGIN already defined!")
  endif()
else()
    add_definitions(-DEIGEN_DENSEBASE_PLUGIN=\"${EIGEN_DENSEBASE_PLUGIN_PATH}\")

Comparing to humble release (v2.0.0, which is working), we see there is a missing ament_cmake_export_include_directories-extras.cmake. The line in this PR will make that file generated, and the content would look like this:

# generated from ament_cmake_export_include_directories/cmake/ament_cmake_export_include_directories-extras.cmake.in

set(_exported_include_dirs "${grid_map_core_DIR}/../../../include/grid_map_core")

# append include directories to grid_map_core_INCLUDE_DIRS
# warn about not existing paths
if(NOT _exported_include_dirs STREQUAL "")
  find_package(ament_cmake_core QUIET REQUIRED)
  foreach(_exported_include_dir ${_exported_include_dirs})
    if(NOT IS_DIRECTORY "${_exported_include_dir}")
      message(WARNING "Package 'grid_map_core' exports the include directory '${_exported_include_dir}' which doesn't exist")
    endif()
    normalize_path(_exported_include_dir "${_exported_include_dir}")
    list(APPEND grid_map_core_INCLUDE_DIRS "${_exported_include_dir}")
  endforeach()
endif()

When searching grid_map_core from cmake, it will then state:

Found grid_map_core 2.3.0: /opt/ros/jazzy/include/grid_map_core;/usr/include/eigen3

instead of just:

Found grid_map_core 2.3.0: /usr/include/eigen3

[Ryanf55]

Can you please review the alternative patch at #475 and associated comments on the issue?

[matlabbe]

I just realized that I was using the "old way" to include the library with grid_map_core_INCLUDE_DIRS and grid_map_core_LIBRARIES, which are not defined anymore. We should use target grid_map_core::grid_map_core instead.

find_package(grid_map_core REQUIRED)
target_link_libraries(my_app 
  PRIVATE 
  grid_map_core::grid_map_core
)

When using the correct target (grid_map_core::grid_map_core), it includes the include directory. The original branch (ros2 or rolling) would still fail afterwards when building files unrelated to grid_map_core because the whole cmake project will include the definitions (without linking to that target):

<command-line>: fatal error: grid_map_core/eigen_plugins/FunctorsPlugin.hpp: No such file or directory
compilation terminated.

The patch #475 fixes that issue. I can successfully build my downstream project.

I'll close this PR as it is already fixed by #475.