[CMake] Fwd: Per-Component value for CPACK_PACKAGING_INSTALL_PREFIX with RPM Generator

[Sam Lunt]

I am trying to set a per-component value for
CPACK_PACKAGING_INSTALL_PREFIX when using the RPM generator, but I'm
not having any success.

The CMake documentation for CPACK_RPM_<COMPONENT>_PACKAGE_PREFIX says
that "May be used to set per component CPACK_PACKAGING_INSTALL_PREFIX
for relocatable RPM packages." However, this doesn't seem to be the
case (though I may be misunderstanding something).

Here is a simple CMakeLists that demonstrates the problem:

    cmake_minimum_required(VERSION 3.8)

    project(FooBar
        VERSION 0.1.0
    )

    add_executable(foo foo.cpp)
    add_executable(bar bar.cpp)

    include(GNUInstallDirs)
    install(TARGETS foo
        DESTINATION ${CMAKE_INSTALL_BINDIR}
       COMPONENT Foo_Comp
    )

    install(TARGETS bar
        DESTINATION ${CMAKE_INSTALL_BINDIR}
        COMPONENT Bar_Comp
    )

    set(CPACK_PACKAGE_VERSION_MAJOR ${FooBar_VERSION_MAJOR})
    set(CPACK_PACKAGE_VERSION_MINOR ${FooBar_VERSION_MINOR})
    set(CPACK_PACKAGE_VERSION_PATCH ${FooBar_VERSION_PATCH})

    set(CPACK_PACKAGE_RELOCATABLE ON)
    set(CPACK_PACKAGING_INSTALL_PREFIX "/tmp/foobar")

    set(CPACK_RPM_COMPONENT_INSTALL ON)
    #set(CPACK_RPM_FOO_COMP_PACKAGE_PREFIX "/tmp/foo")
    #set(CPACK_RPM_BAR_COMP_PACKAGE_PREFIX "/tmp/bar")

    set(CPACK_RPM_EXCLUDE_FROM_AUTO_FILELIST_ADDITION "/tmp")

    include(CPack)

As is, the example works fine: when the target install is built, the
executables are installed to
${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_BINDIR}, and when the RPM is
generated and used to install the files, they go to
${CPACK_PACKAGING_INSTALL_PREFIX}/${CMAKE_INSTALL_BINDIR}.
Importantly, the RPM is relocatable (i.e. --prefix and --relocate are
no longer supported with the rpm command).

The issue is when the commented-out lines are uncommented. Instead of
installing each component to its respective packaging prefix, they are
still installed using CPACK_PACKAGING_INSTALL_PREFIX, but now they are
no longer relocatable.

If the install commands are changed to:

    install(TARGETS foo
        DESTINATION "/tmp/foo/${CMAKE_INSTALL_BINDIR}"
        COMPONENT Foo_Comp
    )

    install(TARGETS bar
        DESTINATION "/tmp/bar/${CMAKE_INSTALL_BINDIR}"
        COMPONENT Bar_Comp
    )

then the packages are relocatable and RPM installs them as expected,
but CMAKE_INSTALL_PREFIX no longer works correctly.

Is there a way that I can have relocatable RPMs with different
per-component packaging install prefix without breaking the install
target?

Thanks in advance for any help.