[question] How do you use conan.tools.cmake.CMake with conanbuildinfo.cmake?

[jkleve]

I set up my cmake project to include conanbuildinfo.cmake and do the basic setup. There's a lot of useful stuff in there so I'd like to keep using it. I switched from conans.CMake to conan.tools.cmake.CMake and now when I try to create the package I get:

ERROR: my-example/0.1: Error in build() method, line 90
        cmake = CMake(self)
        ConanException: Usage of toolchain is only supported with 'cmake_find_package' or 'cmake_find_package_multi' generators

So my question is why is the cmake generator forbidden with conan.tools.cmake.CMake?

See cmake.py:13

def _validate_recipe(conanfile):
    forbidden_generators = ["cmake", "cmake_multi"]
    if any(it in conanfile.generators for it in forbidden_generators):
        raise ConanException("Usage of toolchain is only supported with 'cmake_find_package'"
                             " or 'cmake_find_package_multi' generators")

[memsharded]

Hi @jkleve

They are completely different integrations. The conan.tools.cmake import CMake works together with CMakeDeps and CMakeToolchain, and implements a fully transparent integration that does not use a conanbuildinfo.cmake file at all. The new CMake for example assumes that CMakeToolchain created the conan_toolchain.cmake file (or at least a file telling the toolchain). The new conan.tools.cmake is intended to fully replace the legacy integrations, and it is the only one that will remain in 2.0, all the others have already been removed.

[jkleve]

That was my incline. I think I've read quite a bit of the documentation and this wasn't clear to me. We should mark the old CMake build helper as going away in 2.0 and/or mention this is not to be used with the newer CMake method. The second point is covered by the ConanException but I don't believe the documentation covers it.

[memsharded]

Moving this to the "docs" repo.

We should mark the old CMake build helper as going away in 2.0 and/or mention this is not to be used with the newer CMake method

This is not easy to do in production code, because that is the declared "stable" integration, so we cannot pollute it with warnings or anything, because users will complain. So it needs to be a docs thing (which is also in a bad place at the moment, we know, because it is not easy to swap the old by new without breaking somethings, because for example all recipes in ConanCenter still uses the old integrations)

[jkleve]

We can go ahead and close this if you'd like. It's documented in code.