I am failing at adding a meson project to a cmake project as a dependent library

Question

I need to add a meson project (specifically jose) to my project where I am using cmake.

This post: CMake: How to build external projects and include their targets is trying to acheive a similar goal but now that time has pass the recommendation is to use FetchContent. However, that does seem to only apply to other cmake projects, not "foreign" projects. At least, I failed to see how to run meson in the examples.

So. I am trying to use ExternalProject_Add, which works perfectly (configure and eventually build jose). But conceptually there is an issue since I also need to add the jose library to target_link_libraries. However, the library is not yet built when cmake configures the whole project.

I think I understand that I need to have jose built during the global cmake configuration.

I try to use execute_process and ExternalProject_Add_Step but failed at making them to work properly. Here are the details

ExternalProject_Add(
  jose
  UPDATE_COMMAND ""
  PATCH_COMMAND ""

  SOURCE_DIR  ${CMAKE_CURRENT_SOURCE_DIR}/jose

  # Configure
  CONFIGURE_HANDLED_BY_BUILD true
  CONFIGURE_COMMAND meson setup ${CMAKE_CURRENT_SOURCE_DIR}/jose --prefix=${INSTALL_DIR} --pkg-config-path ${CMAKE_CURRENT_BINARY_DIR}/vcpkg_installed/x64-linux/lib/pkgconfig

  BUILD_COMMAND ninja

  INSTALL_COMMAND ""
  TEST_COMMAND ""

)

set(jose_BINARY_DIR "${BINARY_DIR}")
ExternalProject_Add_Step(jose build
    COMMENT "Building jose project..."
    COMMAND ${CMAKE_COMMAND} --build ${jose_BINARY_DIR}
    RESULT_VARIABLE jose_build_result
    OUTPUT_QUIET
    DEPENDEES download update
    WORKING_DIRECTORY ${jose_BINARY_DIR}
)

add_dependencies(${CMAKE_PROJECT_NAME} jose)

There are 2 problems:

• target_link_libraries is still trying to look for josé before it is being built
• if I remove josé from target_link_libraries (for testing) the ExternalProject_Add_Step fails with a message indicating that add_custom_command is trying to add a duplicate custom rule (in jose-build.rule).

My questions

• Am I on the right track with ExternalProject_Add_Step
• If so, how to make it executed before target_link_libraries is evaluated