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Merge pull request #1028 from gracicot/develop
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Added support for string_view in C++17
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@nlohmann
nlohmann authored Jun 23, 2018
2 parents ed6a068 + 14e6278 commit bf348ca
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Showing 6 changed files with 152 additions and 4 deletions.
17 changes: 17 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 @@ -72,6 +72,23 @@ void from_json(const BasicJsonType& j, typename BasicJsonType::string_t& s)
s = *j.template get_ptr<const typename BasicJsonType::string_t*>();
}

template <
typename BasicJsonType, typename CompatibleStringType,
enable_if_t <
is_compatible_string_type<BasicJsonType, CompatibleStringType>::value and
not std::is_same<typename BasicJsonType::string_t,
CompatibleStringType>::value,
int > = 0 >
void from_json(const BasicJsonType& j, CompatibleStringType& s)
{
if (JSON_UNLIKELY(not j.is_string()))
{
JSON_THROW(type_error::create(302, "type must be string, but is " + std::string(j.type_name())));
}

s = *j.template get_ptr<const typename BasicJsonType::string_t*>();
}

template<typename BasicJsonType>
void from_json(const BasicJsonType& j, typename BasicJsonType::number_float_t& val)
{
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10 changes: 10 additions & 0 deletions include/nlohmann/detail/conversions/to_json.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,16 @@ struct external_constructor<value_t::string>
j.m_value = std::move(s);
j.assert_invariant();
}

template<typename BasicJsonType, typename CompatibleStringType,
enable_if_t<not std::is_same<CompatibleStringType, typename BasicJsonType::string_t>::value,
int> = 0>
static void construct(BasicJsonType& j, const CompatibleStringType& str)
{
j.m_type = value_t::string;
j.m_value.string = j.template create<typename BasicJsonType::string_t>(str);
j.assert_invariant();
}
};

template<>
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20 changes: 20 additions & 0 deletions include/nlohmann/detail/meta.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -120,6 +120,17 @@ struct is_compatible_object_type_impl<true, RealType, CompatibleObjectType>
std::is_constructible<typename RealType::mapped_type, typename CompatibleObjectType::mapped_type>::value;
};

template<bool B, class RealType, class CompatibleStringType>
struct is_compatible_string_type_impl : std::false_type {};

template<class RealType, class CompatibleStringType>
struct is_compatible_string_type_impl<true, RealType, CompatibleStringType>
{
static constexpr auto value =
std::is_same<typename RealType::value_type, typename CompatibleStringType::value_type>::value and
std::is_constructible<RealType, CompatibleStringType>::value;
};

template<class BasicJsonType, class CompatibleObjectType>
struct is_compatible_object_type
{
Expand All @@ -130,6 +141,15 @@ struct is_compatible_object_type
typename BasicJsonType::object_t, CompatibleObjectType >::value;
};

template<class BasicJsonType, class CompatibleStringType>
struct is_compatible_string_type
{
static auto constexpr value = is_compatible_string_type_impl <
conjunction<negation<std::is_same<void, CompatibleStringType>>,
has_value_type<CompatibleStringType>>::value,
typename BasicJsonType::string_t, CompatibleStringType >::value;
};

template<typename BasicJsonType, typename T>
struct is_basic_json_nested_type
{
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4 changes: 2 additions & 2 deletions include/nlohmann/json.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2829,9 +2829,9 @@ class basic_json
not detail::is_basic_json<ValueType>::value
#ifndef _MSC_VER // fix for issue #167 operator<< ambiguity under VS2015
and not std::is_same<ValueType, std::initializer_list<typename string_t::value_type>>::value
#endif
#if defined(JSON_HAS_CPP_17)
#if defined(JSON_HAS_CPP_17) && _MSC_VER <= 1914

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@garethsb

garethsb Mar 24, 2020

Contributor

Putting a preprocessor condition on _MSC_VER inside the #ifndef _MSC_VER cannot be what was intended, can it?
and not std::is_same<ValueType, typename std::string_view>::value
#endif
#endif
, int >::type = 0 >
operator ValueType() const
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51 changes: 49 additions & 2 deletions single_include/nlohmann/json.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -354,6 +354,17 @@ struct is_compatible_object_type_impl<true, RealType, CompatibleObjectType>
std::is_constructible<typename RealType::mapped_type, typename CompatibleObjectType::mapped_type>::value;
};

template<bool B, class RealType, class CompatibleStringType>
struct is_compatible_string_type_impl : std::false_type {};

template<class RealType, class CompatibleStringType>
struct is_compatible_string_type_impl<true, RealType, CompatibleStringType>
{
static constexpr auto value =
std::is_same<typename RealType::value_type, typename CompatibleStringType::value_type>::value and
std::is_constructible<RealType, CompatibleStringType>::value;
};

template<class BasicJsonType, class CompatibleObjectType>
struct is_compatible_object_type
{
Expand All @@ -364,6 +375,15 @@ struct is_compatible_object_type
typename BasicJsonType::object_t, CompatibleObjectType >::value;
};

template<class BasicJsonType, class CompatibleStringType>
struct is_compatible_string_type
{
static auto constexpr value = is_compatible_string_type_impl <
conjunction<negation<std::is_same<void, CompatibleStringType>>,
has_value_type<CompatibleStringType>>::value,
typename BasicJsonType::string_t, CompatibleStringType >::value;
};

template<typename BasicJsonType, typename T>
struct is_basic_json_nested_type
{
Expand Down Expand Up @@ -980,6 +1000,23 @@ void from_json(const BasicJsonType& j, typename BasicJsonType::string_t& s)
s = *j.template get_ptr<const typename BasicJsonType::string_t*>();
}

template <
typename BasicJsonType, typename CompatibleStringType,
enable_if_t <
is_compatible_string_type<BasicJsonType, CompatibleStringType>::value and
not std::is_same<typename BasicJsonType::string_t,
CompatibleStringType>::value,
int > = 0 >
void from_json(const BasicJsonType& j, CompatibleStringType& s)
{
if (JSON_UNLIKELY(not j.is_string()))
{
JSON_THROW(type_error::create(302, "type must be string, but is " + std::string(j.type_name())));
}

s = *j.template get_ptr<const typename BasicJsonType::string_t*>();
}

template<typename BasicJsonType>
void from_json(const BasicJsonType& j, typename BasicJsonType::number_float_t& val)
{
Expand Down Expand Up @@ -1324,6 +1361,16 @@ struct external_constructor<value_t::string>
j.m_value = std::move(s);
j.assert_invariant();
}

template<typename BasicJsonType, typename CompatibleStringType,
enable_if_t<not std::is_same<CompatibleStringType, typename BasicJsonType::string_t>::value,
int> = 0>
static void construct(BasicJsonType& j, const CompatibleStringType& str)
{
j.m_type = value_t::string;
j.m_value.string = j.template create<typename BasicJsonType::string_t>(str);
j.assert_invariant();
}
};

template<>
Expand Down Expand Up @@ -13588,9 +13635,9 @@ class basic_json
not detail::is_basic_json<ValueType>::value
#ifndef _MSC_VER // fix for issue #167 operator<< ambiguity under VS2015
and not std::is_same<ValueType, std::initializer_list<typename string_t::value_type>>::value
#endif
#if defined(JSON_HAS_CPP_17)
#if defined(JSON_HAS_CPP_17) && _MSC_VER <= 1914
and not std::is_same<ValueType, typename std::string_view>::value
#endif
#endif
, int >::type = 0 >
operator ValueType() const
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54 changes: 54 additions & 0 deletions test/src/unit-conversions.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,17 @@ using nlohmann::json;
#include <unordered_set>
#include <valarray>

#if (defined(__cplusplus) && __cplusplus >= 201703L) || (defined(_HAS_CXX17) && _HAS_CXX17 == 1) // fix for issue #464
#define JSON_HAS_CPP_17
#define JSON_HAS_CPP_14
#elif (defined(__cplusplus) && __cplusplus >= 201402L) || (defined(_HAS_CXX14) && _HAS_CXX14 == 1)
#define JSON_HAS_CPP_14
#endif

#if defined(JSON_HAS_CPP_17)
#include <string_view>
#endif

TEST_CASE("value conversion")
{
SECTION("get an object (explicit)")
Expand Down Expand Up @@ -344,6 +355,13 @@ TEST_CASE("value conversion")
std::string s = j.get<std::string>();
CHECK(json(s) == j);
}
#if defined(JSON_HAS_CPP_17)
SECTION("std::string_view")
{
std::string_view s = j.get<std::string_view>();
CHECK(json(s) == j);
}
#endif

SECTION("exception in case of a non-string type")
{
Expand Down Expand Up @@ -385,6 +403,34 @@ TEST_CASE("value conversion")
json(json::value_t::number_float).get<json::string_t>(),
"[json.exception.type_error.302] type must be string, but is number");
}

#if defined(JSON_HAS_CPP_17)
SECTION("exception in case of a non-string type using string_view")
{
CHECK_THROWS_AS(json(json::value_t::null).get<std::string_view>(), json::type_error&);
CHECK_THROWS_AS(json(json::value_t::object).get<std::string_view>(), json::type_error&);
CHECK_THROWS_AS(json(json::value_t::array).get<std::string_view>(), json::type_error&);
CHECK_THROWS_AS(json(json::value_t::boolean).get<std::string_view>(), json::type_error&);
CHECK_THROWS_AS(json(json::value_t::number_integer).get<std::string_view>(), json::type_error&);
CHECK_THROWS_AS(json(json::value_t::number_unsigned).get<std::string_view>(), json::type_error&);
CHECK_THROWS_AS(json(json::value_t::number_float).get<std::string_view>(), json::type_error&);

CHECK_THROWS_WITH(json(json::value_t::null).get<std::string_view>(),
"[json.exception.type_error.302] type must be string, but is null");
CHECK_THROWS_WITH(json(json::value_t::object).get<std::string_view>(),
"[json.exception.type_error.302] type must be string, but is object");
CHECK_THROWS_WITH(json(json::value_t::array).get<std::string_view>(),
"[json.exception.type_error.302] type must be string, but is array");
CHECK_THROWS_WITH(json(json::value_t::boolean).get<std::string_view>(),
"[json.exception.type_error.302] type must be string, but is boolean");
CHECK_THROWS_WITH(json(json::value_t::number_integer).get<std::string_view>(),
"[json.exception.type_error.302] type must be string, but is number");
CHECK_THROWS_WITH(json(json::value_t::number_unsigned).get<std::string_view>(),
"[json.exception.type_error.302] type must be string, but is number");
CHECK_THROWS_WITH(json(json::value_t::number_float).get<std::string_view>(),
"[json.exception.type_error.302] type must be string, but is number");
}
#endif
}

SECTION("get a string (implicit)")
Expand All @@ -398,6 +444,14 @@ TEST_CASE("value conversion")
CHECK(json(s) == j);
}

#if defined(JSON_HAS_CPP_17)
SECTION("std::string_view")
{
std::string_view s = j;
CHECK(json(s) == j);
}
#endif

SECTION("std::string")
{
std::string s = j;
Expand Down

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