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🚧 conversions for std::optional
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@nlohmann @karzhenkov
nlohmann authored and karzhenkov committed Jan 7, 2023
1 parent 4c6cde7 commit f6f169e
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23 changes: 23 additions & 0 deletions include/nlohmann/detail/conversions/from_json.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,14 @@
#include <utility> // pair, declval
#include <valarray> // valarray

#ifdef JSON_HAS_CPP_17
#if __has_include(<optional>)
#include <optional>
#elif __has_include(<experimental/optional>)
#include <experimental/optional>
#endif
#endif

#include <nlohmann/detail/exceptions.hpp>
#include <nlohmann/detail/macro_scope.hpp>
#include <nlohmann/detail/meta/cpp_future.hpp>
Expand All @@ -43,6 +51,21 @@ inline void from_json(const BasicJsonType& j, typename std::nullptr_t& n)
n = nullptr;
}

#ifdef JSON_HAS_CPP_17
template<typename BasicJsonType, typename T>
void from_json(const BasicJsonType& j, std::optional<T>& opt)
{
if (j.is_null())
{
opt = std::nullopt;
}
else
{
opt = j.template get<T>();
}
}
#endif

// overloads for basic_json template parameters
template < typename BasicJsonType, typename ArithmeticType,
enable_if_t < std::is_arithmetic<ArithmeticType>::value&&
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24 changes: 24 additions & 0 deletions include/nlohmann/detail/conversions/to_json.hpp
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Expand Up @@ -24,6 +24,14 @@
#include <nlohmann/detail/meta/type_traits.hpp>
#include <nlohmann/detail/value_t.hpp>

#ifdef JSON_HAS_CPP_17
#if __has_include(<optional>)
#include <optional>
#elif __has_include(<experimental/optional>)
#include <experimental/optional>
#endif
#endif

NLOHMANN_JSON_NAMESPACE_BEGIN
namespace detail
{
Expand Down Expand Up @@ -260,6 +268,22 @@ struct external_constructor<value_t::object>
// to_json //
/////////////

#ifdef JSON_HAS_CPP_17
template<typename BasicJsonType, typename T,
enable_if_t<std::is_constructible<BasicJsonType, T>::value, int> = 0>
void to_json(BasicJsonType& j, const std::optional<T>& opt)
{
if (opt.has_value())
{
j = *opt;
}
else
{
j = nullptr;
}
}
#endif

template<typename BasicJsonType, typename T,
enable_if_t<std::is_same<T, typename BasicJsonType::boolean_t>::value, int> = 0>
inline void to_json(BasicJsonType& j, T b) noexcept
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47 changes: 47 additions & 0 deletions single_include/nlohmann/json.hpp
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Expand Up @@ -169,6 +169,14 @@
#include <utility> // pair, declval
#include <valarray> // valarray

#ifdef JSON_HAS_CPP_17
#if __has_include(<optional>)
#include <optional>
#elif __has_include(<experimental/optional>)
#include <experimental/optional>
#endif
#endif

// #include <nlohmann/detail/exceptions.hpp>
// __ _____ _____ _____
// __| | __| | | | JSON for Modern C++
Expand Down Expand Up @@ -4603,6 +4611,21 @@ inline void from_json(const BasicJsonType& j, typename std::nullptr_t& n)
n = nullptr;
}

#ifdef JSON_HAS_CPP_17
template<typename BasicJsonType, typename T>
void from_json(const BasicJsonType& j, std::optional<T>& opt)
{
if (j.is_null())
{
opt = std::nullopt;
}
else
{
opt = j.template get<T>();
}
}
#endif

// overloads for basic_json template parameters
template < typename BasicJsonType, typename ArithmeticType,
enable_if_t < std::is_arithmetic<ArithmeticType>::value&&
Expand Down Expand Up @@ -5334,6 +5357,14 @@ class tuple_element<N, ::nlohmann::detail::iteration_proxy_value<IteratorType >>
// #include <nlohmann/detail/value_t.hpp>


#ifdef JSON_HAS_CPP_17
#if __has_include(<optional>)
#include <optional>
#elif __has_include(<experimental/optional>)
#include <experimental/optional>
#endif
#endif

NLOHMANN_JSON_NAMESPACE_BEGIN
namespace detail
{
Expand Down Expand Up @@ -5570,6 +5601,22 @@ struct external_constructor<value_t::object>
// to_json //
/////////////

#ifdef JSON_HAS_CPP_17
template<typename BasicJsonType, typename T,
enable_if_t<std::is_constructible<BasicJsonType, T>::value, int> = 0>
void to_json(BasicJsonType& j, const std::optional<T>& opt)
{
if (opt.has_value())
{
j = *opt;
}
else
{
j = nullptr;
}
}
#endif

template<typename BasicJsonType, typename T,
enable_if_t<std::is_same<T, typename BasicJsonType::boolean_t>::value, int> = 0>
inline void to_json(BasicJsonType& j, T b) noexcept
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67 changes: 67 additions & 0 deletions tests/src/unit-conversions.cpp
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Expand Up @@ -32,6 +32,14 @@ using nlohmann::json;
DOCTEST_CLANG_SUPPRESS_WARNING_PUSH
DOCTEST_CLANG_SUPPRESS_WARNING("-Wexit-time-destructors")

#ifdef JSON_HAS_CPP_17
#if __has_include(<optional>)
#include <optional>
#elif __has_include(<experimental/optional>)
#include <experimental/optional>
#endif
#endif

TEST_CASE("value conversion")
{
SECTION("get an object (explicit)")
Expand Down Expand Up @@ -1569,4 +1577,63 @@ TEST_CASE("JSON to enum mapping")
}
}

#ifdef JSON_HAS_CPP_17
TEST_CASE("std::optional")
{
SECTION("null")
{
json j_null;
std::optional<std::string> opt_null;

CHECK(json(opt_null) == j_null);
CHECK(std::optional<std::string>(j_null) == std::nullopt);
}

SECTION("string")
{
json j_string = "string";
std::optional<std::string> opt_string = "string";

CHECK(json(opt_string) == j_string);
CHECK(std::optional<std::string>(j_string) == opt_string);
}

SECTION("bool")
{
json j_bool = true;
std::optional<bool> opt_bool = true;

CHECK(json(opt_bool) == j_bool);
CHECK(std::optional<bool>(j_bool) == opt_bool);
}

SECTION("number")
{
json j_number = 1;
std::optional<int> opt_int = 1;

CHECK(json(opt_int) == j_number);
CHECK(std::optional<int>(j_number) == opt_int);
}

SECTION("array")
{
json j_array = {1, 2, nullptr};
std::vector<std::optional<int>> opt_array = {{1, 2, std::nullopt}};

CHECK(json(opt_array) == j_array);
CHECK(std::vector<std::optional<int>>(j_array) == opt_array);
}

SECTION("object")
{
json j_object = {{"one", 1}, {"two", 2}, {"zero", nullptr}};
std::map<std::string, std::optional<int>> opt_object {{"one", 1}, {"two", 2}, {"zero", std::nullopt}};

CHECK(json(opt_object) == j_object);
CHECK(std::map<std::string, std::optional<int>>(j_object) == opt_object);
}
}
#endif

DOCTEST_CLANG_SUPPRESS_WARNING_POP

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