Full fix for broken yaml detection

[SlawekNowy]

Fixes #1858

[linux-foundation-easycla]

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• ✅ login: SlawekNowy (aa4d263, f14e3af, ed9b4b7, e1a127d, c67164e)

[remia]

Thanks for the PR @SlawekNowy !

[tobim]

With this patch I get:

CMake Error in tests/cpu/CMakeLists.txt:
  Imported target "yaml-cpp" includes non-existent path
    "yaml-cpp_INCLUDE_DIR-NOTFOUND"
  in its INTERFACE_INCLUDE_DIRECTORIES.  Possible reasons include:
  * The path was deleted, renamed, or moved to another location.
  * An install or uninstall procedure did not complete successfully.
  * The installation package was faulty and references files it does not
  provide.

CMake Error in src/OpenColorIO/CMakeLists.txt:
  Imported target "yaml-cpp" includes non-existent path
    "yaml-cpp_INCLUDE_DIR-NOTFOUND"
  in its INTERFACE_INCLUDE_DIRECTORIES.  Possible reasons include:
  * The path was deleted, renamed, or moved to another location.
  * An install or uninstall procedure did not complete successfully.
  * The installation package was faulty and references files it does not
  provide.

A better approach would be to switch to yaml-cpp::yaml-cpp in the code and create a backwards compatibility alias in case that target does not exist:

if(TARGET yaml-cpp AND NOT TARGET yaml-cpp::yaml-cpp)
  add_library(yaml-cpp::yaml-cpp ALIAS yaml-cpp)
endif()

Afaics the get_target_property lines can be dropped.

[SlawekNowy]

A better approach would be to switch to yaml-cpp::yaml-cpp in the code and create a backwards compatibility alias in case that target does not exist:

if(TARGET yaml-cpp AND NOT TARGET yaml-cpp::yaml-cpp)
  add_library(yaml-cpp::yaml-cpp ALIAS yaml-cpp)
endif()

Do we really need to break root CMakeLists? Though the bug is still concerning.

[tobim]

Do we really need to break root CMakeLists?

I don't understand what you mean by break? Do you want me to submit another PR?

[SlawekNowy]

I meant that "Does this change break anything using this file?"

[SlawekNowy]

@tobim also what system do you use?

[SlawekNowy]

Ok from beginning. The minimum requirement for yaml-cpp is 0.7.0. Its installed cmake module exports that lib as yaml-cpp. In 0.8.0 this is changed to yaml-cpp::yaml-cpp prompting this very PR. I am afraid that your (@tobim) patch instead of mine would fail builds both on 0.7 and 0.8 version of yaml.

[SlawekNowy]

A better approach would be to switch to yaml-cpp::yaml-cpp in the code and create a backwards compatibility alias in case that target does not exist:

if(TARGET yaml-cpp AND NOT TARGET yaml-cpp::yaml-cpp)
  add_library(yaml-cpp::yaml-cpp ALIAS yaml-cpp)
endif()

Do we really need to break root CMakeLists? Though the bug is still concerning.

That code is already present in the affected file, and yet in some setups it still isn't sufficient.

[remia]

Sorry for adding yet another version but wouldn't it be simpler to make the alias target right after the initial find_package, similar to what we already do for Findexpat.cmake? Did a quick test here, only tested on macOS with 0.8.0 though.

[SlawekNowy]

I theorize that was what @tobim was trying to say, and I agree @remia. Confirmed working on Linux host with yaml-cpp 0.8.0 and Linux chroot with yaml-cpp 0.7.0

[tobim]

Indeed, and that is already implemented in #1891, among some other cleanups.

[remia]

@SlawekNowy Is this PR now superseded by #1891 ? Do you think we should close this one?

[SlawekNowy]

Indeed. Closing in favor of #1891.