[SOLVED] How-to create a Conan 2.0 package that consists only of CMake source code and allows consumers to include its CMake source files?

Issue

Using Conan v2.0.14 and CMake v3.27.8 I'd like to create a reusable "only-CMake-code" Conan package (foo) that can be consumed by another CMake project (bar) and allows to use the include([...]) command in the CMakeLists.txt of the bar project in order to pull in CMake modules defined in foo.

I assume (I'm totally new to Conan, but have good knowledge of CMake) the way to go is to create a proper CMake package (either via Conan or via CMakeLists.txt) for foo that generates a foo-config.cmake file. This should allow bar to find foo using the find_package(foo REQUIRED) command. Afterwards a CMake variable defined in foo-config.cmake file should be accessible in bar, allowing the following in the CMakeLists.txt of bar:

include("${foo_ROOT}/foo_module.cmake")

My current conanfile.py of foo looks as follows:

from os import path
from conan import ConanFile
from conan.tools.cmake import CMake, CMakeToolchain
from conan.tools.files import copy

required_conan_version = ">=2.0.14"

class Recipe(ConanFile):
    name = "foo"
    version = "latest"

    exports_sources = "tool/cmake/*"
    no_copy_source = True

    def generate(self):
        tc = CMakeToolchain(self)
        tc.generate()

    def package(self):
        cmake = CMake(self)
        cmake.install()

        copy(self, "tool/cmake/*", self.source_folder, self.package_folder)

    def package_info(self):
        self.cpp_info.bindirs = []
        self.cpp_info.libdirs = []

Running conan create outputs the following error:

cmake.install()
ConanException: build_type setting should be defined.

I do understand the message, but now I think maybe I've chosen the wrong approach. I'd like to simply install foo using a CMake Package Config, but do not want to care about build configs, toolchains, etc. at all. I'm also unsure whether foo also requires a CMakeLists.txt (maybe with additional install commands) in order to be properly installable via Conan.

I've read the related question How to use CMake file provided by a Conan package? and its answers but it didn't help me.

Solution

There are a couple of examples in the docs that might be useful:

• using a macro from a regular dependency requires, see this docs docs.conan.io/2/examples/graph/requires/…
• Using a macro from a tool_requires

If the intent is to reuse some script, it might not be necessary to do a find_package() and make the xxx-config.cmake scripts bring the modules to use, but it is probably easier to do a plain include(myscript), because the toolchains like CMakeToolchain will put the necessary paths in the right variables so this works (the dependency recipe has to define self.cpp_info.builddirs to point to the folders containing the scripts)

Answered By - drodri

Answer Checked By - Clifford M. (WPSolving Volunteer)