find_package failing on prescan stage

[SMorettini]

After migrating to Fprime 3, the find_package(rclcpp QUIET) is failing with the following errors:

-- Target build toolchain/platform: Linux/Linux
-- Including /home/user/project_path...../Fprime/cmake/platform/Linux.cmake
-- Installation directory: /home/user/project_path...../build-artifacts
-- Including library /home/user/project_path..... with manifests 
-- Using PYTHON_EXECUTABLE: /usr/bin/python3
CMake Warning at /opt/ros/foxy/share/rcutils/cmake/ament_cmake_export_libraries-extras.cmake:116 (message):
  Package 'rcutils' exports library 'dl' which couldn't be found
Call Stack (most recent call first):
  /opt/ros/foxy/share/rcutils/cmake/rcutilsConfig.cmake:41 (include)
  /opt/ros/foxy/share/rosidl_runtime_c/cmake/ament_cmake_export_dependencies-extras.cmake:21 (find_package)
  /opt/ros/foxy/share/rosidl_runtime_c/cmake/rosidl_runtime_cConfig.cmake:41 (include)
  /opt/ros/foxy/share/builtin_interfaces/cmake/ament_cmake_export_dependencies-extras.cmake:21 (find_package)
  /opt/ros/foxy/share/builtin_interfaces/cmake/builtin_interfacesConfig.cmake:41 (include)
  /opt/ros/foxy/share/rcl_interfaces/cmake/ament_cmake_export_dependencies-extras.cmake:21 (find_package)
  /opt/ros/foxy/share/rcl_interfaces/cmake/rcl_interfacesConfig.cmake:41 (include)
  /opt/ros/foxy/share/rcl/cmake/ament_cmake_export_dependencies-extras.cmake:21 (find_package)
  /opt/ros/foxy/share/rcl/cmake/rclConfig.cmake:41 (include)
  /opt/ros/foxy/share/libstatistics_collector/cmake/ament_cmake_export_dependencies-extras.cmake:21 (find_package)
  /opt/ros/foxy/share/libstatistics_collector/cmake/libstatistics_collectorConfig.cmake:41 (include)
  /opt/ros/foxy/share/rclcpp/cmake/ament_cmake_export_dependencies-extras.cmake:21 (find_package)
  /opt/ros/foxy/share/rclcpp/cmake/rclcppConfig.cmake:41 (include)
  CMakeLists.txt:78 (find_package)


-- Using all available rosidl_typesupport_c: rosidl_typesupport_fastrtps_c;rosidl_typesupport_introspection_c
-- Found rosidl_adapter: 1.2.1 (/opt/ros/foxy/share/rosidl_adapter/cmake)
-- Using all available rosidl_typesupport_cpp: rosidl_typesupport_fastrtps_cpp;rosidl_typesupport_introspection_cpp
CMake Warning at /opt/ros/foxy/share/libyaml_vendor/cmake/ament_cmake_export_libraries-extras.cmake:116 (message):
  Package 'libyaml_vendor' exports library 'yaml' which couldn't be found
Call Stack (most recent call first):
  /opt/ros/foxy/share/libyaml_vendor/cmake/libyaml_vendorConfig.cmake:41 (include)
  /opt/ros/foxy/share/rcl_yaml_param_parser/cmake/ament_cmake_export_dependencies-extras.cmake:21 (find_package)
  /opt/ros/foxy/share/rcl_yaml_param_parser/cmake/rcl_yaml_param_parserConfig.cmake:41 (include)
  /opt/ros/foxy/share/rcl/cmake/ament_cmake_export_dependencies-extras.cmake:21 (find_package)
  /opt/ros/foxy/share/rcl/cmake/rclConfig.cmake:41 (include)
  /opt/ros/foxy/share/libstatistics_collector/cmake/ament_cmake_export_dependencies-extras.cmake:21 (find_package)
  /opt/ros/foxy/share/libstatistics_collector/cmake/libstatistics_collectorConfig.cmake:41 (include)
  /opt/ros/foxy/share/rclcpp/cmake/ament_cmake_export_dependencies-extras.cmake:21 (find_package)
  /opt/ros/foxy/share/rclcpp/cmake/rclcppConfig.cmake:41 (include)
  CMakeLists.txt:78 (find_package)


-- Found rmw_implementation_cmake: 1.0.3 (/opt/ros/foxy/share/rmw_implementation_cmake/cmake)
-- Using RMW implementation 'rmw_fastrtps_cpp' as default
CMake Error at /opt/ros/foxy/share/rcl_logging_spdlog/cmake/ament_cmake_export_dependencies-extras.cmake:21 (find_package):
  By not providing "Findspdlog.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "spdlog", but
  CMake did not find one.

  Could not find a package configuration file provided by "spdlog" with any
  of the following names:

    spdlogConfig.cmake
    spdlog-config.cmake

  Add the installation prefix of "spdlog" to CMAKE_PREFIX_PATH or set
  "spdlog_DIR" to a directory containing one of the above files.  If "spdlog"
  provides a separate development package or SDK, be sure it has been
  installed.
Call Stack (most recent call first):
  /opt/ros/foxy/share/rcl_logging_spdlog/cmake/rcl_logging_spdlogConfig.cmake:41 (include)
  /opt/ros/foxy/share/rcl/cmake/ament_cmake_export_dependencies-extras.cmake:21 (find_package)
  /opt/ros/foxy/share/rcl/cmake/rclConfig.cmake:41 (include)
  /opt/ros/foxy/share/libstatistics_collector/cmake/ament_cmake_export_dependencies-extras.cmake:21 (find_package)
  /opt/ros/foxy/share/libstatistics_collector/cmake/libstatistics_collectorConfig.cmake:41 (include)
  /opt/ros/foxy/share/rclcpp/cmake/ament_cmake_export_dependencies-extras.cmake:21 (find_package)
  /opt/ros/foxy/share/rclcpp/cmake/rclcppConfig.cmake:41 (include)
  CMakeLists.txt:78 (find_package)


-- Configuring incomplete, errors occurred!
See also "/home/user/project_path...../build-fprime-automatic-native-ut/prescan/CMakeFiles/CMakeOutput.log".
See also "/home/user/project_path...../build-fprime-automatic-native-ut/prescan/CMakeFiles/CMakeError.log".
CMake Error at /home/user/project_path...../Fprime/cmake/prescan.cmake:103 (message):
  Failed to run prescan, cannot continue.
Call Stack (most recent call first):
  /home/user/project_path...../Fprime/cmake/FPrime.cmake:78 (perform_prescan)
  CMakeLists.txt:48 (include)


-- Configuring incomplete, errors occurred!

After some tests and debugging I find out that if I add the following condition the CMake run smoothly:

if (NOT DEFINED FPRIME_PRESCAN)
    find_package(rclcpp QUIET) 
endif()

Instead, if I use the following code I obtain again the error posted above:

if (DEFINED FPRIME_PRESCAN)
    find_package(rclcpp QUIET) 
endif()

It seems that on the prescan the find_package(rclcpp QUIET) fails. Any idea of why it is happening? Is there in the prescan something that could influence the find_package?

From my research it seems that some environment variables are cleaned and so the prescan is not able to find packages. But I'm not sure about that.

[LeStarch]

#1642 is the crux of the issue. In short, your CMAKE variables aren't being fully forwarded over.

[LeStarch]

if (NOT DEFINED FPRIME_PRESCAN)
    find_package(rclcpp QUIET) 
endif()

Is the appropriate fix for packages that do not define FPP files inside.

[SMorettini]

It's this solution still valid? I saw that in the last versions of Fprime the FPRIME_PRESCAN is never defined. Should I use FPRIME_SUB_BUILD_TARGETS instead?

Moreover FPRIME_PRESCAN is still used in a couple of places(https://github.com/search?q=repo%3Anasa%2Ffprime%20FPRIME_PRESCAN&type=code), if I understood correctly the changes I think it should be removed. Am I right?

[LeStarch]

In short, I believe so. We moved from prescanning (specific subbuild) to generic subbuilds, so we could reuse the code.

We should take an action to review the use of FPRIME_PRESCAN above! Good catch!