Building a node with a custom IDL message with conan2

Question

I am migrating from conan1 to conan2. Unfortunately my ROS node which depends on a custom IDL message interface is not built successfully anymore in conan2. The linking stage fails with:

undefined reference to `rosidl_message_type_support_t const* rosidl_typesupport_cpp::get_message_type_support_handle<ros2_custom_message_interface::msg::CustomMessage_<std::allocator<void> > >()'`

Using a combination of grep and find I tracked down that rosidl_message_type_support_t const is defined in the file /opt/ros/humble/include/rosidl_runtime_c/rosidl_runtime_c/message_type_support_struct.h

How can I get cmake to take the file into account? I tried adding rosidl_runtime_c in find_package, ament_target_dependencies and target_link_libraries options without success.

Note: Before I execute the build with conan, I am sourcing the ROS environment in my terminal.

My CMakeLists.txt file is:

cmake_minimum_required(VERSION 3.5)
project(ros2_custom_message_node)

if(NOT CMAKE_CXX_STANDARD)
  set(CMAKE_CXX_STANDARD 14)
  set(CMAKE_CXX_STANDARD_REQUIRED ON)
  set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
endif()

if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  add_compile_options(-Wall -Wextra -Wpedantic)
endif()

set(TARGET_NAME custom_message_node)
add_executable(${TARGET_NAME} src/main.cpp)
install(TARGETS ${TARGET_NAME})

# Parts that are more specific to ROS 2.
find_package(ament_cmake_auto REQUIRED)
find_package(rclcpp REQUIRED)
find_package(rclcpp_components REQUIRED)
ament_auto_find_build_dependencies()

ament_target_dependencies(${TARGET_NAME} rclcpp ros2_custom_message_interface)

if(BUILD_TESTING)
  find_package(ament_lint_auto REQUIRED)
  ament_lint_auto_find_test_dependencies()
endif()

# export dependencies correctly
ament_auto_package()

and my conanfile.py is

from conan import ConanFile
from conan.tools.cmake import CMake

class Ros2CustomMessageNode(ConanFile):
    name = "ros2_custom_message_node"
    version = "0.1.0"
    settings = "os", "compiler", "build_type", "arch"
    generators = "CMakeToolchain", "CMakeDeps"
    exports_sources = "CMakeLists.txt", "package.xml", "src/*"

    def requirements(self):
        self.requires("ros2_custom_message_interface/0.1.0")

    def build(self):
        cmake = CMake(self)
        cmake.configure()
        cmake.build()
        cmake.install()

Answer 1

I might be late to answer here but better late than never :D

I think you are missing the find_package(ros2_custom_message_interface) call in your CMakeLists. Conan generates the CMake target config files with the CMakeDeps generator and the CMakeToolchain is able to inject those files to be discoverable by CMake. But still you have to find_package() and link the dependency target via ament_target_dependencies().

Something in the line of:

cmake_minimum_required(VERSION 3.5)
project(ros2_custom_message_node)
...
find_package(ros2_custom_message_interface)
...
ament_target_dependencies(${TARGET_NAME} rclcpp ros2_custom_message_interface)
...

Hope it helps!