conversion of described classes supports private members

Author: grisumbras

include/boost/json/conversion.hpp

@@ -302,7 +302,7 @@ struct is_null_like
 /** Determine if `T` should be treated as a described class
 
     Described classes are serialised as objects with an element for each
-    described public data member. A described class should not have described
+    described data member. A described class should not have described
     bases or non-public members.<br>
 
     Or more formally, given `L`, a class template
@@ -335,10 +335,10 @@ struct is_null_like
     @endcode
 
     Users can also specialize the trait for their own types _with_ described
-    bases to enable this conversion implementation. In this case the class will
-    be serialized in a flattened way, that is members of bases will be
-    serialized as direct elements of the object, and no nested objects will be
-    created for bases.
+    bases or described non-public data members to enable this conversion
+    implementation. In this case the class will be serialized in a flattened
+    way, that is members of bases will be serialized as direct elements of the
+    object, and no nested objects will be created for bases.
 
     @see <a href="https://www.boost.org/doc/libs/develop/libs/describe/doc/html/describe.html">Boost.Describe</a>.
 */

include/boost/json/detail/parse_into.hpp

@@ -949,9 +949,7 @@ struct struct_element_list_impl
     template< class D >
     using helper = described_member_t<T, D>;
 
-    using type = mp11::mp_transform<
-        helper,
-        describe::describe_members<T, describe::mod_public> >;
+    using type = mp11::mp_transform< helper, described_members<T> >;
 };
 template< class T >
 using struct_element_list = typename struct_element_list_impl<T>::type;
@@ -960,20 +958,17 @@ using struct_element_list = typename struct_element_list_impl<T>::type;
 
 template< class T >
 using struct_element_list = mp11::mp_transform_q<
-    mp11::mp_bind_front< described_member_t, T >,
-    describe::describe_members<T, describe::mod_public> >;
+    mp11::mp_bind_front< described_member_t, T >, described_members<T> >;
 
 #endif
 
 struct struct_accessor
 {
     template< class T, class I >
     auto operator()( T* t, I ) const
-        -> described_member_t<T,
-             mp11::mp_at<
-                 describe::describe_members<T, describe::mod_public>, I> >*
+        -> described_member_t<T, mp11::mp_at< described_members<T>, I> >*
     {
-        using Ds = describe::describe_members<T, describe::mod_public>;
+        using Ds = described_members<T>;
         using D = mp11::mp_at<Ds, I>;
         return &(t->*D::pointer);
     }
@@ -1008,7 +1003,7 @@ class converting_handler<described_class_conversion_tag, V, P>
 
     std::string key_;
 
-    using Dm = describe::describe_members<V, describe::mod_public>;
+    using Dm = described_members<V>;
 
     handler_tuple< converting_handler, struct_element_list<V> > handlers_;
     int inner_active_ = -1;

include/boost/json/detail/value_from.hpp

@@ -155,8 +155,7 @@ value_from_impl( no_conversion_tag, value&, T&&, Ctx const& )
 template< class Ctx, class T >
 struct from_described_member
 {
-    using Ds = describe::describe_members<
-        remove_cvref<T>, describe::mod_public | describe::mod_inherited>;
+    using Ds = described_members< remove_cvref<T> >;
 
     object& obj;
     Ctx const& ctx;

include/boost/json/detail/value_to.hpp

@@ -342,8 +342,7 @@ value_to_impl(
 template< class Ctx, class T, bool non_throwing = true >
 struct to_described_member
 {
-    using Ds = describe::describe_members<
-        T, describe::mod_public | describe::mod_inherited>;
+    using Ds = described_members<T>;
 
     using result_type = mp11::mp_eval_if_c<
         !non_throwing, T, system::result, T>;

include/boost/json/impl/conversion.hpp

@@ -297,6 +297,10 @@ using described_member_t = remove_cvref<decltype(
 
 #endif
 
+template< class T >
+using described_members = describe::describe_members<
+    T, describe::mod_any_access | describe::mod_inherited>;
+
 // user conversion (via tag_invoke)
 template< class Ctx, class T, class Dir >
 using user_conversion_category = mp11::mp_cond<

test/parse_into.cpp

@@ -52,11 +52,37 @@ bool operator==( Y const& y1, Y const& y2 )
     return y1.v == y2.v && y1.m == y2.m;
 }
 
+struct Z : X
+{
+    Z() = default;
+    Z(X x, bool b) : X(x), d(b)
+    {}
+
+private:
+    bool d = false;
+
+    friend
+    bool operator==( Z const& z1, Z const& z2 )
+    {
+        X const& x1 = z1;
+        X const& x2 = z2;
+        return (x1 == x2) && z1.d == z2.d;
+    }
+
+    BOOST_DESCRIBE_CLASS(Z, (X), (), (), (d))
+};
+
+
 BOOST_DEFINE_ENUM_CLASS(E, x, y, z)
 
 namespace boost {
 namespace json {
 
+template<>
+struct is_described_class<Z>
+    : std::true_type
+{ };
+
 class parse_into_test
 {
 public:
@@ -340,6 +366,9 @@ class parse_into_test
         testParseInto<Y>( {} );
         testParseInto<Y>( { { { 1, 1.0f, "one" }, { 2, 2.0f, "two" } }, { { "one", { 1, 1.1f, "1" } }, { "two", { 2, 2.2f, "2" } } } } );
 
+        testParseInto<Z>( {} );
+        testParseInto<Z>( { {1, 3.14f, "hello"}, true } );
+
         testParseIntoErrors<X>( error::not_object, 1 );
         testParseIntoErrors<X>(
             error::unknown_name,

test/value_from.cpp

@@ -183,8 +183,18 @@ BOOST_DESCRIBE_STRUCT(T10, (), (n, d))
 struct T11 : T10
 {
     std::string s;
+
+    void
+    set_b(bool v)
+    {
+        b = v;
+    }
+
+private:
+    bool b;
+
+    BOOST_DESCRIBE_CLASS(T11, (T10), (s), (), (b))
 };
-BOOST_DESCRIBE_STRUCT(T11, (T10), (s))
 
 //----------------------------------------------------------
 
@@ -488,8 +498,9 @@ class value_from_test
         t11.n = 67;
         t11.d = -.12;
         t11.s = "qwerty";
+        t11.set_b(true);
         jv = value_from( t11, ctx... );
-        BOOST_TEST(( jv == value{{"n", 67}, {"d", -.12}, {"s", "qwerty"}} ));
+        BOOST_TEST(( jv == value{{"n", 67}, {"d", -.12}, {"s", "qwerty"}, {"b", true}} ));
 
         ::value_from_test_ns::E1 e1 = ::value_from_test_ns::E1::a;
         BOOST_TEST( value_from( e1, ctx... ) == "a" );

test/value_to.cpp

@@ -119,8 +119,18 @@ BOOST_DESCRIBE_STRUCT(T6, (), (n, d))
 struct T7 : T6
 {
     std::string s;
+
+    bool
+    get_b() const
+    {
+        return b;
+    }
+
+private:
+    bool b = false;
+
+    BOOST_DESCRIBE_CLASS(T7, (T6), (s), (), (b))
 };
-BOOST_DESCRIBE_STRUCT(T7, (T6), (s))
 
 //----------------------------------------------------------
 
@@ -425,13 +435,14 @@ class value_to_test
                 value_to<::value_to_test_ns::T6>( jv ));
         }
         {
-            value jv = {{"n", 1}, {"d", 2}, {"s", "xyz"}};
+            value jv = {{"n", 1}, {"d", 2}, {"s", "xyz"}, {"b", true}};
             auto res = try_value_to<::value_to_test_ns::T7>(
                 jv, ctx... );
             BOOST_TEST( res );
             BOOST_TEST( res->n == 1 );
             BOOST_TEST( res->d == 2 );
             BOOST_TEST( res->s == "xyz" );
+            BOOST_TEST( res->get_b() == true );
         }
 
         BOOST_TEST_THROWS_WITH_LOCATION(