xetter_cpp_function implementation for std::unique_ptr

Author: rwgk

include/pybind11/pybind11.h

@@ -1445,6 +1445,7 @@ struct xetter_cpp_function<
                         && !std::is_pointer<D>::value   //
                         && !is_std_unique_ptr<D>::value //
                         && !is_std_shared_ptr<D>::value>> {
+
     template <typename PM>
     static cpp_function readonly(PM pm, const handle &hdl) {
         return cpp_function(
@@ -1472,6 +1473,36 @@ struct xetter_cpp_function<
     }
 };
 
+template <typename T, typename D>
+struct xetter_cpp_function<
+    T,
+    D,
+    detail::enable_if_t<
+        detail::type_uses_smart_holder_type_caster<T>::value //
+        && is_std_unique_ptr<D>::value
+        && detail::type_uses_smart_holder_type_caster<typename D::element_type>::value>> {
+
+    template <typename PM>
+    static cpp_function readonly(PM, const handle &) {
+        static_assert(!is_std_unique_ptr<D>::value,
+                      "def_readonly cannot be used for std::unique_ptr members.");
+        return cpp_function{}; // Unreachable.
+    }
+
+    template <typename PM>
+    static cpp_function read(PM pm, const handle &hdl) {
+        return cpp_function(
+            [pm](const std::shared_ptr<T> &c_sp) -> D { return D{std::move(c_sp.get()->*pm)}; },
+            is_method(hdl));
+    }
+
+    template <typename PM>
+    static cpp_function write(PM pm, const handle &hdl) {
+        return cpp_function([pm](T &c, D &&value) { (c.*pm).reset(value.release()); },
+                            is_method(hdl));
+    }
+};
+
 // clang-format off
 
 template <typename type_, typename... options>

tests/test_class_sh_property.cpp

@@ -73,26 +73,10 @@ TEST_SUBMODULE(class_sh_property, m) {
         .def_readonly("m_cptr_readonly", &Outer::m_cptr)
         .def_readwrite("m_cptr_readwrite", &Outer::m_cptr)
 
-        .def_property( //
-            "m_uqmp_readwrite",
-            [](const std::shared_ptr<Outer> &self) {
-                return std::unique_ptr<Field>(std::move(self->m_uqmp));
-            },
-            [](Outer &self, std::unique_ptr<Field> uqmp) {
-                self.m_uqmp = std::move(uqmp); //
-            })
-        .def_property( //
-            "m_uqcp_readwrite",
-            [](const std::shared_ptr<Outer> &self) {
-                return std::unique_ptr<const Field>(std::move(self->m_uqcp));
-            },
-            [](Outer &self, std::unique_ptr<const Field> uqcp) {
-                self.m_uqcp = std::move(uqcp); //
-            })
-        // .def_readonly("m_uqmp_readonly", &Outer::m_uqmp) // Compilation Error.
-        // .def_readwrite("m_uqmp_readwrite", &Outer::m_uqmp)
-        // .def_readonly("m_uqcp_readonly", &Outer::m_uqcp) // Compilation Error.
-        // .def_readwrite("m_uqcp_readwrite", &Outer::m_uqcp)
+        // .def_readonly("m_uqmp_readonly", &Outer::m_uqmp) // Custom compilation Error.
+        .def_readwrite("m_uqmp_readwrite", &Outer::m_uqmp)
+        // .def_readonly("m_uqcp_readonly", &Outer::m_uqcp) // Custom compilation Error.
+        .def_readwrite("m_uqcp_readwrite", &Outer::m_uqcp)
 
         .def_readwrite("m_shmp_readonly", &Outer::m_shmp)
         .def_readwrite("m_shmp_readwrite", &Outer::m_shmp)