[feature] Allow specifying an install component for the CMake helper

One is capable of passing --component to CMake’s --install command, however the same functionality is missing from the CMake helper’s install() method: https://docs.conan.io/en/latest/reference/build_helpers/cmake.html#install

Since Conan does not package CMake configs generated by recipes, in many cases the recipe can just define the runtime component and there won’t be a need to rmdir additional files.

I suggest adding a component=None argument to this method and restructuring it in terms of the cmake generated cmake_install.cmake script. The code would look something like this:

def install(... component=None):
    if component is not None:
        if isinstance(component, str):
            component_args = [f"-DCOMPONENT={component}"]
        else:
            component_args = [f"-DCOMPONENT={c}" for c in component]
    else:
        component_args = [""]
    for comp in component_args:
        self.run(f"cmake -DBUILD_TYPE={build_type} {comp} -P cmake_install.cmake", cwd=bindir)

or maybe a new method like install_component() with a required positional argument, if such a break for v2 is not desirable.
find -name conanfile.py -exec grep -nHEe '\.install\([^)]' {} \; shows no usage for this method being used with any arguments in CCI though.

• I’ve read the CONTRIBUTING guide.

[stas-neverov]

Here is a workaround that seems to work:

    def package(self):
        self.run(f"cmake --install {self.build_folder} --component component1"
                 f" --prefix {os.path.join(self.package_folder, 'component1')}")
    
    def package_info(self):
        self.cpp_info.builddirs.append("component1")

[jwillikers]

I think this is still a pertinent issue for the new CMake build helper as projects may use component-based installs and the default install component may not install the necessary files. Adding the ability to specify a component argument to the CMake.install() command would be ideal. This could just translate to cmake --install ... --component <specified_component>. I have a use case right now where this is necessary as the default component actually installs a bunch of things that should not be installed but are because they are included from various subprojects.