Move pybind11-utils to own folder. Add tests for shared_cpp_owner.

tests/python/test_shared_cpp_owner.cpp

@@ -0,0 +1,67 @@
+#include "pybind11_utils/shared_cpp_owner.h"
+
+#include <pybind11/pybind11.h>
+
+#include <tuple>
+#include <unordered_map>
+
+namespace py = pybind11;
+using namespace pybind11::literals;
+
+class Base;
+static std::unordered_map<std::string, Base*> bases;
+
+class Base {
+    std::string name_;
+
+public:
+    Base(std::string const& name) : name_{name} { bases[name] = this; }
+    virtual std::string fn() const = 0;
+    virtual ~Base() { bases.erase(name_); }
+};
+
+MO2_PYBIND11_SHARED_CPP_HOLDER(Base);
+
+class CppBase : public Base {
+public:
+    using Base::Base;
+    std::string fn() const override { return "CppBase::fn()"; }
+};
+
+class PyBase : public Base {
+public:
+    using Base::Base;
+    std::string fn() const override { PYBIND11_OVERRIDE_PURE(std::string, Base, fn, ); }
+};
+
+PYBIND11_MODULE(shared_cpp_owner, m)
+{
+    static std::shared_ptr<Base> base_ptr;
+
+    py::class_<Base, PyBase, std::shared_ptr<Base>>(m, "Base")
+        .def(py::init<std::string>())
+        .def("fn", &Base::fn);
+
+    m.def("is_alive", [](std::string const& name) {
+        return bases.find(name) != bases.end();
+    });
+
+    m.def("create", [](std::string const& name) -> std::shared_ptr<Base> {
+        return std::make_shared<CppBase>(name);
+    });
+    m.def("create_and_store", [](std::string const& name) {
+        base_ptr = std::make_shared<CppBase>(name);
+        return base_ptr;
+    });
+    m.def("store", [](std::shared_ptr<Base> ptr) {
+        base_ptr = ptr;
+    });
+    m.def("clear", []() {
+        base_ptr.reset();
+    });
+
+    m.def("call_fn", [](std::string const& name) {
+        auto it = bases.find(name);
+        return it != bases.end() ? it->second->fn() : "";
+    });
+}