This is a quick but rather subtle issue. My CMake list file goes like:

if (NOT TARGET Spglib::symspg)
    find_package(Spglib CONFIG)
    if (NOT Spglib_FOUND)
        message(STATUS "Using bundled spglib sources")
        add_subdirectory(${PROJECT_SOURCE_DIR}/.. _deps/spglib-build)
    endif ()
endif ()

If I pip install from scratch it works just fine, i.e. the add_subdirectory is used. But if I run pip install again, then it picks up the current installation and it goes through find_package even though it is later removed at the install stage when the previous version is uninstalled.

I think the issue is with working around NO_CMAKE_INSTALL_PREFIX, but it is weird, shouldn't that point to tmp folder that would not interfere? Otherwise I did not configure any prefix for it to use. Any clues on what's happening here and how to work around it?

I believe the issue is with: