[question] Should cmake_additional_variables_prefixes generate {{prefix}}_FOUND and {{prefix}}_VERSION?

[AbrilRBS]

What is your question?

In conan-io/conan-center-index#26063, a gap in the current CMakeDeps cmake_additional_variables_prefixes property shows up:

• Upstream defines uppercase variants of the FOUND and VERSION variables, alongside the rest of them, so I used cmake_additional_variables_prefixes to generate those.
• This works great, up until the point where any of the FOUND/VERSION variables is used. Conan does not generate them by default, leaving CMake to do it on its own

But a issue arises as cmake_additional_variables_prefixes does not generate extra versions of FOUND and VERSION, which forces me to define them in the CMakeToolchain to make the recipe compile

cc/ @franramirez688

Have you read the CONTRIBUTING guide?

• I've read the CONTRIBUTING guide

[memsharded]

Just to make sure, the _FOUND variables are only generated for the modules, but not for Config files:

{% if is_module %}
        include(FindPackageHandleStandardArgs)
        set({{ file_name }}_FOUND 1)

Is this issue related to modules? Does curl uses zstd by default using a module and not a config.cmake file?

[valgur]

The issue is quite widely applicable, I would say. There's a number of recipes on CCI that export a CMake config and also upper-case CMake vars:

• armadillo
• bullet3
• ceres-solver
• freetype
• gnutls
• jasper
• libgeotiff
• ncurses
• openal
• openal-soft
• openjpeg
• openscenegraph
• openssl
• osgearth
• xapian-core
• xz_utils

Also, a sizable fraction of patches on CCI are for injecting Conan dependencies into CMake projects, where the project does something like find_package(Eigen ...) and then continues to use it like if(EIGEN_FOUND) .... It could be worked around by setting deps.set_property("eigen", "cmake_find_mode", "module"), but it would be great if that could be avoided.

On the other hand, generating XYZ_FOUND and XYZ_VERSION might indeed be somewhat difficult for CMakeDeps, since it's something that is handled by CMake itself, usually.