daw_json_traits.h

Go to the documentation of this file.

// Copyright (c) Darrell Wright
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// Official repository: https://github.com/beached/daw_json_link
//
 
#pragma once
 
#include "daw/json/impl/version.h"
 
#include "daw/json/concepts/daw_nullable_value.h"
#include "daw/json/daw_json_data_contract.h"
#include "daw/json/impl/daw_json_default_constuctor.h"
#include "daw/json/impl/daw_json_enums.h"
#include "daw/json/impl/daw_json_link_types_aggregate.h"
#include "daw/json/impl/daw_json_name.h"
#include "daw/json/impl/daw_json_req_helper.h"
#include "daw/json/impl/daw_json_type_options.h"
 
#include <daw/cpp_17.h>
#include <daw/daw_callable.h>
#include <daw/daw_cpp20_concept.h>
#include <daw/daw_fwd_pack_apply.h>
#include <daw/daw_move.h>
#include <daw/daw_traits.h>
 
#include <string>
#include <string_view>
#include <type_traits>
 
namespace daw {
  struct use_default;
} // namespace daw
 
/***
 * Customization point traits
 *
 */
namespace daw::json {
  inline namespace DAW_JSON_VER {
    namespace json_details {
      template<template<typename...> typename Trait, typename... Params>
      struct ident_trait {
        using type = Trait<Params...>;
      };
 
      DAW_JSON_MAKE_REQ_TRAIT( has_op_bool_v,
                               static_cast<bool>( std::declval<T>( ) ) );
 
      DAW_JSON_MAKE_REQ_TRAIT( has_op_star_v, *std::declval<T>( ) );
 
      template<typename Constructor, typename... Args>
      struct constructor_cannot_be_invoked;
 
      template<typename Constructor, typename... Args>
      struct construction_result
        : daw::conditional_t<
            daw::is_callable_v<Constructor, Args...>,
            std::invoke_result<Constructor, Args...>,
            daw::traits::identity<
              constructor_cannot_be_invoked<Constructor, Args...>>> {};
    } // namespace json_details
 
    namespace json_details {
      template<typename JsonMember>
      using without_name = typename JsonMember::without_name;
 
      template<typename JsonMember, JSONNAMETYPE NewName, bool Cond>
      using copy_name_when = daw::conditional_t<
        Cond, typename JsonMember::template with_name<NewName>, JsonMember>;
 
      template<typename JsonMember, JSONNAMETYPE NewName>
      using copy_name_when_noname =
        copy_name_when<JsonMember, NewName, is_no_name_v<JsonMember>>;
    } // namespace json_details
 
    namespace json_details {
      DAW_JSON_MAKE_REQ_TYPE_ALIAS_TRAIT(
        is_json_map_alias_v,
        json_data_contract_trait_t<T>::i_am_a_json_map_alias );
 
      DAW_JSON_MAKE_REQ_TYPE_ALIAS_TRAIT( has_switcher_v, T::switcher );
 
      DAW_JSON_MAKE_REQ_TYPE_ALIAS_TRAIT(
        force_aggregate_construction_test1,
        json_data_contract<T>::force_aggregate_construction );
 
      DAW_JSON_MAKE_REQ_TRAIT( force_aggregate_construction_test2,
                               T::force_aggregate_construction );
    } // namespace json_details
    /***
     * This trait can be specialized such that when class being returned has
     * non-move/copyable members the construction can be done with { } instead
     * of a callable.  This is a blunt object and probably should not be used
     * add a type alias named force_aggregate_construction to your
     * json_data_contract specialization
     * @tparam T type to specialize
     */
    template<typename T>
    inline constexpr bool force_aggregate_construction_v =
      json_details::force_aggregate_construction_test1<T> or
      json_details::force_aggregate_construction_test2<T>;
 
    namespace json_details {
      template<typename, typename = void>
      struct json_constructor;
 
      template<typename T>
      struct json_constructor<T, std::void_t<typename T::constructor_t>> {
        using type = typename T::constructor_t;
      };
 
      template<typename T>
      using json_constructor_t = typename json_constructor<T>::type;
 
      template<typename, typename = void>
      struct json_result;
 
      template<typename T>
      struct json_result<T, std::void_t<typename T::parse_to_t>> {
        using type = typename T::parse_to_t;
      };
 
      template<typename T>
      using json_result_t = typename json_result<T>::type;
 
      template<typename, typename = void>
      struct json_base_type;
 
      template<typename T>
      struct json_base_type<T, std::void_t<json_result_t<T>>> {
        using type = json_result_t<T>;
      };
 
      template<typename T>
      using json_base_type_t = typename json_base_type<T>::type;
 
      DAW_JSON_MAKE_REQ_TYPE_ALIAS_TRAIT(
        is_default_default_constructor_type_v,
        T::i_am_the_default_default_constructor_type );
 
      DAW_JSON_MAKE_REQ_TYPE_ALIAS_TRAIT( has_stateless_allocator_v,
                                          T::has_stateless_allocator );
 
      DAW_JSON_MAKE_REQ_TYPE_ALIAS_TRAIT(
        has_data_contract_constructor_v, json_data_contract<T>::constructor_t );
 
      template<typename>
      inline constexpr bool must_be_class_member_v = false;
    } // namespace json_details
 
    template<typename Constructor, typename T, typename ParseState>
    inline constexpr bool should_construct_explicitly_v =
      not json_details::has_data_contract_constructor_v<T> and
      ( force_aggregate_construction_v<T> or
        json_details::is_default_default_constructor_type_v<Constructor> or
        not json_details::has_stateless_allocator_v<ParseState> );
 
    template<typename... Ts>
    DAW_CPP20_CONCEPT is_empty_pack_v = sizeof...( Ts ) == 0;
 
    template<typename>
    inline constexpr bool can_single_allocation_string_v = false;
 
    template<typename Char, typename CharTrait, typename Allocator>
    inline constexpr bool can_single_allocation_string_v<
      std::basic_string<Char, CharTrait, Allocator>> = true;
 
    template<typename T>
    using can_single_allocation_string =
      std::bool_constant<can_single_allocation_string_v<T>>;
 
    namespace json_details {
      DAW_JSON_MAKE_REQ_TYPE_ALIAS_TRAIT( is_a_json_type_v,
                                          T::i_am_a_json_type );
 
      template<typename... Ts>
      inline constexpr bool are_json_types_v = ( is_a_json_type_v<Ts> and ... );
 
      DAW_JSON_MAKE_REQ_TYPE_ALIAS_TRAIT( is_an_ordered_member_v,
                                          T::i_am_an_ordered_member );
 
      template<typename T>
      using is_an_ordered_member =
        std::bool_constant<is_an_ordered_member_v<T>>;
 
      DAW_JSON_MAKE_REQ_TYPE_ALIAS_TRAIT( is_a_json_tagged_variant_v,
                                          T::i_am_a_json_tagged_variant );
 
      template<typename T>
      using json_class_constructor_t_impl =
        typename json_data_contract<T>::constructor;
 
      template<typename T>
      using data_contract_constructor_t =
        typename json_data_contract<T>::constructor_t;
 
      template<typename T, typename Default>
      using json_class_constructor_t = daw::detected_or_t<
        typename daw::conditional_t<
          std::is_same_v<use_default, Default>,
          daw::conditional_t<has_data_contract_constructor_v<T>,
                             ident_trait<data_contract_constructor_t, T>,
                             ident_trait<default_constructor, T>>,
          daw::traits::identity<Default>>::type,
        json_class_constructor_t_impl, T>;
 
      DAW_JSON_MAKE_REQ_TRAIT_CUSTOM(
        is_string_view_like_v, ( (void)( std::data( std::declval<T>( ) ) ),
                                 (void)( std::size( std::declval<T>( ) ) ) ) );
 
      static_assert( is_string_view_like_v<std::string_view> );
 
    } // namespace json_details
 
    /***
     * Trait for passively exploiting the zero termination when the type
     * guarantees it.
     */
    template<typename>
    inline constexpr bool is_zero_terminated_string_v = false;
 
    template<typename CharT, typename Traits, typename Alloc>
    inline constexpr bool
      is_zero_terminated_string_v<std::basic_string<CharT, Traits, Alloc>> =
        true;
 
    template<typename T>
    using is_zero_terminated_string =
      std::bool_constant<is_zero_terminated_string_v<T>>;
 
    namespace json_details {
      template<typename ParsePolicy, auto Option>
      using apply_policy_option_t =
        typename ParsePolicy::template SetPolicyOptions<Option>;
 
      template<typename ParsePolicy, typename String, auto Option>
      using apply_zstring_policy_option_t = daw::conditional_t<
        is_zero_terminated_string_v<daw::remove_cvref_t<String>>,
        apply_policy_option_t<ParsePolicy, Option>, ParsePolicy>;
 
      template<typename String>
      inline constexpr bool is_mutable_string_v =
        not std::is_const_v<std::remove_pointer_t<std::remove_reference_t<
          decltype( std::data( std::declval<String &&>( ) ) )>>>;
 
      /*
      template<typename ParsePolicy, typename String, auto OptionMutable,
               auto OptionImmutable>
      using apply_mutable_policy = daw::conditional_t<
        ParsePolicy::allow_temporarily_mutating_buffer( ),
        daw::conditional_t<is_mutable_string_v<String>,
                           apply_policy_option_t<ParsePolicy, OptionMutable>,
                           apply_policy_option_t<ParsePolicy, OptionImmutable>>,
        daw::conditional_t<
          (is_rvalue_string<String> and is_mutable_string_v<String>),
          apply_policy_option_t<ParsePolicy, OptionMutable>,
          apply_policy_option_t<ParsePolicy, OptionImmutable>>>;
          */
    } // namespace json_details
 
    /***
     * Ignore unknown members trait allows the parser to skip unknown members
     * when the default is exact
     * Set to true when data contract has type alias ignore_unknown_members
     */
    DAW_JSON_MAKE_REQ_TYPE_ALIAS_TRAIT_CUSTOM(
      ignore_unknown_members_v, json_data_contract<T>::ignore_unknown_members );
 
    /***
     * A trait to specify that this class, when parsed, will describe all
     * members of the JSON object. Anything not mapped is an error.
     * Either specialize this variable daw::json::is_exact_class_mapping_v, or
     * have a type in your json_data_contract named exact_class_mapping for your
     * type
     */
    DAW_JSON_MAKE_REQ_TYPE_ALIAS_TRAIT_CUSTOM(
      is_exact_class_mapping_v, json_data_contract<T>::exact_class_mapping );
 
    namespace json_details {
      template<typename T, typename ParseState>
      DAW_CPP20_CONCEPT all_json_members_must_exist_v =
        not ignore_unknown_members_v<T> and
        ( is_exact_class_mapping_v<T> or
          ParseState::use_exact_mappings_by_default );
 
      DAW_JSON_MAKE_REQ_TYPE_ALIAS_TRAIT( has_element_type, T::element_type );
 
      template<template<typename...> typename T, typename... Params>
      struct identity_parts {
        using type = T<Params...>;
      };
    } // namespace json_details
 
    /***
     * is_pointer_like is used in json_array to ensure that to_json_data returns
     * a Container/View of the data with the size encoded with it.
     * The std
     */
    template<typename T>
    inline constexpr bool is_pointer_like_v =
      std::is_pointer_v<T> or json_details::has_element_type<T>;
 
    template<typename Tuple, typename = void>
    struct tuple_elements_pack;
 
    template<typename... Ts>
    struct tuple_elements_pack<std::tuple<Ts...>> {
      using type = std::tuple<Ts...>;
 
      static constexpr auto size = sizeof...( Ts );
 
      template<std::size_t Idx>
      using element_t = std::tuple_element_t<Idx, type>;
 
      template<std::size_t Idx, typename Tuple>
      static constexpr decltype( auto ) get( Tuple &&tp ) {
        return std::get<Idx>( DAW_FWD( tp ) );
      }
    };
 
    template<typename... Ts>
    struct tuple_elements_pack<daw::fwd_pack<Ts...>> {
      using type = daw::fwd_pack<Ts...>;
 
      static constexpr auto size = sizeof...( Ts );
 
      template<std::size_t Idx>
      using element_t =
        daw::remove_cvref_t<typename std::tuple_element_t<Idx, type>>;
 
      template<std::size_t Idx, typename Tuple>
      static constexpr decltype( auto ) get( Tuple &&tp ) {
        return DAW_FWD( tp ).template get<Idx>( );
      }
    };
 
    template<typename T>
    inline constexpr bool is_pinned_type_v = not(
      (std::is_copy_constructible_v<T> and std::is_copy_assignable_v<T>) or
      ( std::is_move_constructible_v<T> and std::is_move_assignable_v<T> ) );
 
    namespace json_details {
      template<typename, typename = void>
      inline constexpr bool is_tuple_v = false;
 
      template<typename... Ts>
      inline constexpr bool is_tuple_v<std::tuple<Ts...>> = true;
 
      template<typename T>
      inline constexpr bool
        is_tuple_v<T, typename tuple_elements_pack<T>::type> = true;
 
      template<typename T>
      using unwrapped_t = concepts::nullable_value_type_t<T>;
 
      template<typename T>
      using mapped_type_t = typename T::mapped_type;
 
      template<typename T>
      using key_type_t = typename T::key_type;
 
      // DAW disabling to fix #357
#if true or defined( DAW_JSON_DISABLE_RANDOM )
      template<bool>
      DAW_CPP20_CONCEPT can_be_random_iterator_v = false;
#else
      template<bool IsKnown>
      DAW_CPP20_CONCEPT can_be_random_iterator_v = IsKnown;
#endif
 
      DAW_JSON_MAKE_REQ_TYPE_ALIAS_TRAIT( is_literal_json_type_v,
                                          T::as_string );
 
      template<typename JsonMember>
      using literal_json_type_as_string = typename JsonMember::as_string;
 
      DAW_JSON_MAKE_REQ_TYPE_ALIAS_TRAIT( is_deduced_empty_class_v,
                                          T::i_am_a_deduced_empty_class );
    } // namespace json_details
  } // namespace DAW_JSON_VER
} // namespace daw::json