return_value_policy = copy, but type source is non-copyable

[noacoohen]

Hi.
I'm encountering an issue with my code where I'm trying to bind a Python function to C++ code using Pybind11. The C++ wrapper accepts a std::function with two arguments obj1 & obj2 (both are classes), where one of the arguments, obj2, is non-copyable (obj1 is copyable)
Here's my code snippet:

block_processor.def(py::init([](std::function<void(obj1, obj2&)> processing_function) {
    return new block_processor(processing_function);
}), "processing_function"_a)

When I run my Python code, I encounter the following error:

"return_value_policy = copy, but type obj2 is non-copyable!"

Upon debugging, I've identified that the problem occurs in the Pybind11 file pybind11/detail/type_caster_base.h in the cast function:

static handle cast(const itype &src, return_value_policy policy, handle parent) {
    if (policy == return_value_policy::automatic
        || policy == return_value_policy::automatic_reference) {
        policy = return_value_policy::copy;
    }
    return cast(&src, policy, parent);
}

I cannot simply make obj2 a pointer to work around this issue. Do you have any suggestions on how to handle this situation?