add new is_constructible_* traits used in from_json
is_compatible_* traits were used in from_json, but it made no sense whatsoever. It used to work because of non-SFINAE correctness + json_ref unconstrained variadic template constructor. SFINAE checks are becoming quite complex, we need a specification of some sort describing: * which concepts the library uses * how the conversion to/from json works in detail Having such a specification would really help simplifying the current code (as well as having meaningful checks). Fixes !1299
This commit is contained in:
Théo DELRIEU
parent
dd672939a0
commit
45c8af2c46
4 changed files with 378 additions and 152 deletions
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@ -84,13 +84,13 @@ void from_json(const BasicJsonType& j, typename BasicJsonType::string_t& s)
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}
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template <
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typename BasicJsonType, typename CompatibleStringType,
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typename BasicJsonType, typename ConstructibleStringType,
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enable_if_t <
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is_compatible_string_type<BasicJsonType, CompatibleStringType>::value and
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is_constructible_string_type<BasicJsonType, ConstructibleStringType>::value and
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not std::is_same<typename BasicJsonType::string_t,
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CompatibleStringType>::value,
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ConstructibleStringType>::value,
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int > = 0 >
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void from_json(const BasicJsonType& j, CompatibleStringType& s)
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void from_json(const BasicJsonType& j, ConstructibleStringType& s)
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{
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if (JSON_UNLIKELY(not j.is_string()))
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{
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@ -173,11 +173,11 @@ auto from_json_array_impl(const BasicJsonType& j, std::array<T, N>& arr,
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}
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}
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template<typename BasicJsonType, typename CompatibleArrayType>
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auto from_json_array_impl(const BasicJsonType& j, CompatibleArrayType& arr, priority_tag<1> /*unused*/)
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template<typename BasicJsonType, typename ConstructibleArrayType>
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auto from_json_array_impl(const BasicJsonType& j, ConstructibleArrayType& arr, priority_tag<1> /*unused*/)
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-> decltype(
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arr.reserve(std::declval<typename CompatibleArrayType::size_type>()),
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j.template get<typename CompatibleArrayType::value_type>(),
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arr.reserve(std::declval<typename ConstructibleArrayType::size_type>()),
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j.template get<typename ConstructibleArrayType::value_type>(),
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void())
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{
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using std::end;
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@ -188,12 +188,12 @@ auto from_json_array_impl(const BasicJsonType& j, CompatibleArrayType& arr, prio
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{
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// get<BasicJsonType>() returns *this, this won't call a from_json
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// method when value_type is BasicJsonType
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return i.template get<typename CompatibleArrayType::value_type>();
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return i.template get<typename ConstructibleArrayType::value_type>();
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});
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}
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template <typename BasicJsonType, typename CompatibleArrayType>
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void from_json_array_impl(const BasicJsonType& j, CompatibleArrayType& arr,
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template <typename BasicJsonType, typename ConstructibleArrayType>
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void from_json_array_impl(const BasicJsonType& j, ConstructibleArrayType& arr,
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priority_tag<0> /*unused*/)
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{
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using std::end;
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@ -204,21 +204,21 @@ void from_json_array_impl(const BasicJsonType& j, CompatibleArrayType& arr,
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{
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// get<BasicJsonType>() returns *this, this won't call a from_json
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// method when value_type is BasicJsonType
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return i.template get<typename CompatibleArrayType::value_type>();
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return i.template get<typename ConstructibleArrayType::value_type>();
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});
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}
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template <typename BasicJsonType, typename CompatibleArrayType,
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template <typename BasicJsonType, typename ConstructibleArrayType,
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enable_if_t <
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is_compatible_array_type<BasicJsonType, CompatibleArrayType>::value and
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not is_compatible_object_type<BasicJsonType, CompatibleArrayType>::value and
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not is_compatible_string_type<BasicJsonType, CompatibleArrayType>::value and
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not is_basic_json<CompatibleArrayType>::value,
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is_constructible_array_type<BasicJsonType, ConstructibleArrayType>::value and
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not is_constructible_object_type<BasicJsonType, ConstructibleArrayType>::value and
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not is_constructible_string_type<BasicJsonType, ConstructibleArrayType>::value and
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not is_basic_json<ConstructibleArrayType>::value,
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int > = 0 >
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auto from_json(const BasicJsonType& j, CompatibleArrayType& arr)
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auto from_json(const BasicJsonType& j, ConstructibleArrayType& arr)
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-> decltype(from_json_array_impl(j, arr, priority_tag<3> {}),
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j.template get<typename CompatibleArrayType::value_type>(),
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j.template get<typename ConstructibleArrayType::value_type>(),
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void())
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{
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if (JSON_UNLIKELY(not j.is_array()))
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@ -230,9 +230,9 @@ void())
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from_json_array_impl(j, arr, priority_tag<3> {});
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}
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template<typename BasicJsonType, typename CompatibleObjectType,
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enable_if_t<is_compatible_object_type<BasicJsonType, CompatibleObjectType>::value, int> = 0>
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void from_json(const BasicJsonType& j, CompatibleObjectType& obj)
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template<typename BasicJsonType, typename ConstructibleObjectType,
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enable_if_t<is_constructible_object_type<BasicJsonType, ConstructibleObjectType>::value, int> = 0>
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void from_json(const BasicJsonType& j, ConstructibleObjectType& obj)
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{
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if (JSON_UNLIKELY(not j.is_object()))
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{
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@ -240,13 +240,13 @@ void from_json(const BasicJsonType& j, CompatibleObjectType& obj)
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}
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auto inner_object = j.template get_ptr<const typename BasicJsonType::object_t*>();
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using value_type = typename CompatibleObjectType::value_type;
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using value_type = typename ConstructibleObjectType::value_type;
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std::transform(
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inner_object->begin(), inner_object->end(),
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std::inserter(obj, obj.begin()),
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[](typename BasicJsonType::object_t::value_type const & p)
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{
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return value_type(p.first, p.second.template get<typename CompatibleObjectType::mapped_type>());
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return value_type(p.first, p.second.template get<typename ConstructibleObjectType::mapped_type>());
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});
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}
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@ -68,6 +68,52 @@ using from_json_function = decltype(T::from_json(std::declval<Args>()...));
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template <typename T, typename U>
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using get_template_function = decltype(std::declval<T>().template get<U>());
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// trait checking if JSONSerializer<T>::from_json(json const&, udt&) exists
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template <typename BasicJsonType, typename T, typename = void>
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struct has_from_json : std::false_type {};
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template <typename BasicJsonType, typename T>
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struct has_from_json<BasicJsonType, T,
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enable_if_t<not is_basic_json<T>::value>>
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{
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using serializer = typename BasicJsonType::template json_serializer<T, void>;
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static constexpr bool value =
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is_detected_exact<void, from_json_function, serializer,
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const BasicJsonType&, T&>::value;
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};
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// This trait checks if JSONSerializer<T>::from_json(json const&) exists
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// this overload is used for non-default-constructible user-defined-types
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template <typename BasicJsonType, typename T, typename = void>
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struct has_non_default_from_json : std::false_type {};
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template<typename BasicJsonType, typename T>
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struct has_non_default_from_json<BasicJsonType, T, enable_if_t<not is_basic_json<T>::value>>
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{
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using serializer = typename BasicJsonType::template json_serializer<T, void>;
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static constexpr bool value =
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is_detected_exact<T, from_json_function, serializer,
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const BasicJsonType&>::value;
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};
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// This trait checks if BasicJsonType::json_serializer<T>::to_json exists
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// Do not evaluate the trait when T is a basic_json type, to avoid template instantiation infinite recursion.
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template <typename BasicJsonType, typename T, typename = void>
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struct has_to_json : std::false_type {};
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template <typename BasicJsonType, typename T>
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struct has_to_json<BasicJsonType, T, enable_if_t<not is_basic_json<T>::value>>
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{
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using serializer = typename BasicJsonType::template json_serializer<T, void>;
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static constexpr bool value =
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is_detected_exact<void, to_json_function, serializer, BasicJsonType&,
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T>::value;
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};
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///////////////////
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// is_ functions //
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///////////////////
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@ -123,6 +169,35 @@ template <typename BasicJsonType, typename CompatibleObjectType>
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struct is_compatible_object_type
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: is_compatible_object_type_impl<BasicJsonType, CompatibleObjectType> {};
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template <typename BasicJsonType, typename ConstructibleObjectType,
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typename = void>
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struct is_constructible_object_type_impl : std::false_type {};
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template <typename BasicJsonType, typename ConstructibleObjectType>
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struct is_constructible_object_type_impl <
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BasicJsonType, ConstructibleObjectType,
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enable_if_t<is_detected<mapped_type_t, ConstructibleObjectType>::value and
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is_detected<key_type_t, ConstructibleObjectType>::value >>
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{
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using object_t = typename BasicJsonType::object_t;
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static constexpr bool value =
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std::is_constructible<typename ConstructibleObjectType::key_type,
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typename object_t::key_type>::value and
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std::is_same<typename object_t::mapped_type,
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typename ConstructibleObjectType::mapped_type>::value or
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(has_from_json<BasicJsonType,
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typename ConstructibleObjectType::mapped_type>::value or
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has_non_default_from_json <
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BasicJsonType,
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typename ConstructibleObjectType::mapped_type >::value);
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};
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template <typename BasicJsonType, typename ConstructibleObjectType>
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struct is_constructible_object_type
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: is_constructible_object_type_impl<BasicJsonType,
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ConstructibleObjectType> {};
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template <typename BasicJsonType, typename CompatibleStringType,
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typename = void>
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struct is_compatible_string_type_impl : std::false_type {};
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@ -137,9 +212,28 @@ struct is_compatible_string_type_impl <
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std::is_constructible<typename BasicJsonType::string_t, CompatibleStringType>::value;
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};
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template <typename BasicJsonType, typename CompatibleStringType>
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template <typename BasicJsonType, typename ConstrutibleStringType>
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struct is_compatible_string_type
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: is_compatible_string_type_impl<BasicJsonType, CompatibleStringType> {};
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: is_compatible_string_type_impl<BasicJsonType, ConstrutibleStringType> {};
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template <typename BasicJsonType, typename ConstrutibleStringType,
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typename = void>
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struct is_constructible_string_type_impl : std::false_type {};
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template <typename BasicJsonType, typename ConstrutibleStringType>
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struct is_constructible_string_type_impl <
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BasicJsonType, ConstrutibleStringType,
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enable_if_t<is_detected_exact<typename BasicJsonType::string_t::value_type,
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value_type_t, ConstrutibleStringType>::value >>
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{
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static constexpr auto value =
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std::is_constructible<ConstrutibleStringType,
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typename BasicJsonType::string_t>::value;
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};
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template <typename BasicJsonType, typename ConstrutibleStringType>
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struct is_constructible_string_type
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: is_constructible_string_type_impl<BasicJsonType, ConstrutibleStringType> {};
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template <typename BasicJsonType, typename CompatibleArrayType, typename = void>
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struct is_compatible_array_type_impl : std::false_type {};
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@ -148,18 +242,61 @@ template <typename BasicJsonType, typename CompatibleArrayType>
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struct is_compatible_array_type_impl <
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BasicJsonType, CompatibleArrayType,
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enable_if_t<is_detected<value_type_t, CompatibleArrayType>::value and
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is_detected<iterator_t, CompatibleArrayType>::value >>
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is_detected<iterator_t, CompatibleArrayType>::value and
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// This is needed because json_reverse_iterator has a ::iterator type...
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// Therefore it is detected as a CompatibleArrayType.
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// The real fix would be to have an Iterable concept.
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not is_iterator_traits<
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std::iterator_traits<CompatibleArrayType>>::value >>
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{
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// This is needed because json_reverse_iterator has a ::iterator type...
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// Therefore it is detected as a CompatibleArrayType.
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// The real fix would be to have an Iterable concept.
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static constexpr bool value = not is_iterator_traits<std::iterator_traits<CompatibleArrayType>>::value;
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static constexpr bool value =
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std::is_constructible<BasicJsonType,
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typename CompatibleArrayType::value_type>::value;
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};
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template <typename BasicJsonType, typename CompatibleArrayType>
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struct is_compatible_array_type
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: is_compatible_array_type_impl<BasicJsonType, CompatibleArrayType> {};
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template <typename BasicJsonType, typename ConstructibleArrayType, typename = void>
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struct is_constructible_array_type_impl : std::false_type {};
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template <typename BasicJsonType, typename ConstructibleArrayType>
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struct is_constructible_array_type_impl <
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BasicJsonType, ConstructibleArrayType,
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enable_if_t<std::is_same<ConstructibleArrayType,
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typename BasicJsonType::value_type>::value >>
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: std::true_type {};
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template <typename BasicJsonType, typename ConstructibleArrayType>
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struct is_constructible_array_type_impl <
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BasicJsonType, ConstructibleArrayType,
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enable_if_t<not std::is_same<ConstructibleArrayType,
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typename BasicJsonType::value_type>::value and
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is_detected<value_type_t, ConstructibleArrayType>::value and
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is_detected<iterator_t, ConstructibleArrayType>::value and
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is_complete_type<
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detected_t<value_type_t, ConstructibleArrayType>>::value >>
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{
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static constexpr bool value =
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// This is needed because json_reverse_iterator has a ::iterator type,
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// furthermore, std::back_insert_iterator (and other iterators) have a base class `iterator`...
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// Therefore it is detected as a ConstructibleArrayType.
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// The real fix would be to have an Iterable concept.
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not is_iterator_traits <
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std::iterator_traits<ConstructibleArrayType >>::value and
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(std::is_same<typename ConstructibleArrayType::value_type, typename BasicJsonType::array_t::value_type>::value or
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has_from_json<BasicJsonType,
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typename ConstructibleArrayType::value_type>::value or
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has_non_default_from_json <
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BasicJsonType, typename ConstructibleArrayType::value_type >::value);
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};
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template <typename BasicJsonType, typename ConstructibleArrayType>
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struct is_constructible_array_type
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: is_constructible_array_type_impl<BasicJsonType, ConstructibleArrayType> {};
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template <typename RealIntegerType, typename CompatibleNumberIntegerType,
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typename = void>
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struct is_compatible_integer_type_impl : std::false_type {};
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@ -187,51 +324,6 @@ struct is_compatible_integer_type
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: is_compatible_integer_type_impl<RealIntegerType,
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CompatibleNumberIntegerType> {};
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// trait checking if JSONSerializer<T>::from_json(json const&, udt&) exists
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template <typename BasicJsonType, typename T, typename = void>
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struct has_from_json : std::false_type {};
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template <typename BasicJsonType, typename T>
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struct has_from_json<BasicJsonType, T,
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enable_if_t<not is_basic_json<T>::value>>
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{
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using serializer = typename BasicJsonType::template json_serializer<T, void>;
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static constexpr bool value =
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is_detected_exact<void, from_json_function, serializer,
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const BasicJsonType&, T&>::value;
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};
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// This trait checks if JSONSerializer<T>::from_json(json const&) exists
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// this overload is used for non-default-constructible user-defined-types
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template <typename BasicJsonType, typename T, typename = void>
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struct has_non_default_from_json : std::false_type {};
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template<typename BasicJsonType, typename T>
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struct has_non_default_from_json<BasicJsonType, T, enable_if_t<not is_basic_json<T>::value>>
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{
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using serializer = typename BasicJsonType::template json_serializer<T, void>;
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static constexpr bool value =
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is_detected_exact<T, from_json_function, serializer,
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const BasicJsonType&>::value;
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};
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// This trait checks if BasicJsonType::json_serializer<T>::to_json exists
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// Do not evaluate the trait when T is a basic_json type, to avoid template instantiation infinite recursion.
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template <typename BasicJsonType, typename T, typename = void>
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struct has_to_json : std::false_type {};
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template <typename BasicJsonType, typename T>
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struct has_to_json<BasicJsonType, T, enable_if_t<not is_basic_json<T>::value>>
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{
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using serializer = typename BasicJsonType::template json_serializer<T, void>;
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static constexpr bool value =
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is_detected_exact<void, to_json_function, serializer, BasicJsonType&,
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T>::value;
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};
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template <typename BasicJsonType, typename CompatibleType, typename = void>
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struct is_compatible_type_impl: std::false_type {};
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