embedded module defined in static library is not working

[maruncz]

Hi, i'm struggling to create embedded module that is defined in static library.

CMakeLists.txt:

cmake_minimum_required(VERSION 3.5)

project(pybind-test LANGUAGES CXX)

include(FetchContent)

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

add_subdirectory(pybind11)

add_library(lib STATIC statlib.cpp)
target_link_libraries(lib PRIVATE pybind11::embed)

add_executable(test main.cpp second.cpp)
target_link_libraries(test PRIVATE pybind11::embed lib)

main.cpp

#include <iostream>
#include <pybind11/embed.h>

namespace py = pybind11;

int add_inmain(int i, int j) {
    return i + j;
}

PYBIND11_EMBEDDED_MODULE(inmain, m) {
    m.doc() = "pybind11 example plugin"; // optional module docstring

    m.def("add", &add_inmain, "A function that adds two numbers");
}


int main()
{
    py::scoped_interpreter guard{};

    auto inmain = py::module_::import("inmain");
    std::cout << inmain.attr("add")(1, 2).cast<int>() << std::endl;

    auto second = py::module_::import("second");
    std::cout << second.attr("add")(1, 2).cast<int>() << std::endl;

    auto statlib = py::module_::import("statlib");
    std::cout << second.attr("add")(1, 2).cast<int>() << std::endl;

    return 0;
}

second.cpp

#include <pybind11/embed.h>

int add_second(int i, int j) {
    return i + j;
}

PYBIND11_EMBEDDED_MODULE(second, m) {
    m.doc() = "pybind11 example plugin"; // optional module docstring

    m.def("add", &add_second, "A function that adds two numbers");
}

statlib.cpp

#include <pybind11/embed.h>

int add_statlib(int i, int j) {
    return i + j;
}

PYBIND11_EMBEDDED_MODULE(statlib, m) {
    m.doc() = "pybind11 example plugin"; // optional module docstring

    m.def("add", &add_statlib, "A function that adds two numbers");
}

result

3
3
terminate called after throwing an instance of 'pybind11::error_already_set'
  what():  ModuleNotFoundError: No module named 'statlib'

i'm creating bigger C++ project, where users are able to run "user scripts" written in python.
I'm using static libraries as a way to split up whole project into logical pieces, and one piece was supposed to be my data structures accesible from both python and c++.
Can anyone help me with solution?