Adapt test/CMakeLists.txt for standalone vs. super-project builds

[chandryan]

Adapt test/CMakeLists.txt as discussed in #99:

• by linking against Boost::msm when built as part of the super-project
• with find_package and selective linking when built standalone (might not be required when sticking to build as super-project)

[Flamefire]

If you check if the build happens from the parent directory, why don't you link against the target created there too? I.e. target_link_libraries(boost_msm_tests Boost::msm) can be unconditional and replace the target_include_directories line.

But as you link a lot of other Boost libraries there this won't work as the targets for e.g. Boost::assert will be missing.

What is your intention? Running cmake /path/to/msm or cmake /path/to/msm/test?

For the latter the check needs to be if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR) or it will never match

For the former you could move the logic to the main CML and just add this before target_link_libraries:

if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
    find_package(Boost COMPONENTS serialization any preprocessor type_traits [...] REQUIRED)
endif()

The the tests just link against Boost::msm and the whole if-else here is not required.

I have something similar in Nowide: https://github.com/boostorg/nowide/blob/c05f07fedf95cadbb8402f0af62c6333313758cf/CMakeLists.txt#L84-L97

There I just search for Boost in general, assume a full build with all libraries available and link against the header-target Boost::boost In your case that could be:

if(BOOST_SUPERPROJECT_SOURCE_DIR)
  target_link_libraries(boost_msm
  INTERFACE
    Boost::any
    Boost::assert
    Boost::bind
    Boost::circular_buffer
    Boost::config
    Boost::core
    Boost::function
    Boost::fusion
    Boost::mp11
    Boost::mpl
    Boost::parameter
    Boost::phoenix
    Boost::preprocessor
    Boost::proto
    Boost::serialization
    Boost::tuple
    Boost::type_traits
    Boost::typeof
)
else()
  # Standalone build, requires (almost) all (header-only) Boost libraries to be installed, see above list
  if(NOT TARGET Boost::boost)
    find_package(Boost 1.56 REQUIRED)
  endif()
  target_link_libraries(boost_msm INTERFACE Boost::boost)
endif()

[chandryan]

Thank you for your suggestions for cleaning up the CMakeList.txt's, I appreciate it :)

The intention was the former: Calling cmake from msm, though I just tried out building the tests as part of the super-project and it works well for me - I'll stick to that in the future.

The use case of building the tests standalone was rather due to missing knowledge about Boost on my side than something useful. MSM is the first Boost project I contributed to and when I first set it up, I neither invoked b2 properly, nor did I know about the approach using the super-project for building and testing (thanks again for pointing that out).
Those contents in test/CMakeLists.txt were the initial result of running the tests standalone with a half-baked Boost installation on my machine.

Despite my need of running the tests standalone having vanished, I guess the option to build MSM standalone might be useful. I'll create another PR for this :)

[chandryan]

The PR is here: #107

Would you like to take another look @Flamefire ?