Support for disabling optional dependencies even if they can be found.

more precise description in: https://github.com/mesonbuild/meson/issues/8224#issuecomment-763809674

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continuation of #2452 Seems like this is not solved. #2411 was closed and not merged. Even with #3376 it actually requires meson.build to do the correct thing (which it often does not or the build script is a mix of correct and wrong).

You probably want to have a look at CMAKE_DISABLE_FIND_PACKAGE_<PackageName> from CMake to actually learn from it. On a different but related issue: I also saw people suggesting/looking for something like <PackageName>_DIR from CMake

[mensinda]

So, if I understand correctly, the main issue here is that some projects do stuff like:

someDep = dependency('someDep', required: false)

if someDep.found()
  # Do stuff you want to explicitly disable even if someDep is found
  # and the user did not provide another toggle for this condition
endif

If this is the case, I would suggest trying to find a solution for this particular use case, instead of arguing why/if exactly, CMAKE_DISABLE_FIND_PACKAGE is bad. Also, we could argue if we want to actually do something about this / if we actually recognize this as a problem. Debating some CMake design decisions won’t be to anyone’s benefit.

[eli-schwartz]

I have actually, for real, told people “cmake sucks, don’t use cmake. Cmake lets you do nonsense like DISABLE_FIND_PACKAGE instead of proper options. Use meson instead.”

It would feel pretty weird to me if meson then went around and added support for this misfeature.