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Provide fallback for missing char8_t support (#4736)

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This commit is contained in:
Sergiu Deitsch
2025-04-23 18:36:41 +02:00
committed by GitHub
parent 85df7ed593
commit 756ca22ec5
4 changed files with 39 additions and 18 deletions
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5
include/nlohmann/detail/conversions/from_json.hpp
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@@ -539,7 +539,10 @@ inline void from_json(const BasicJsonType& j, std_fs::path& p)
JSON_THROW(type_error::create(302, concat("type must be string, but is ", j.type_name()), &j));
}
const auto& s = *j.template get_ptr<const typename BasicJsonType::string_t*>();
#ifdef JSON_HAS_CPP_20
// Checking for C++20 standard or later can be insufficient in case the
// library support for char8_t is either incomplete or was disabled
// altogether. Use the __cpp_lib_char8_t feature test instead.
#if defined(__cpp_lib_char8_t) && (__cpp_lib_char8_t >= 201907L)
p = std_fs::path(std::u8string_view(reinterpret_cast<const char8_t*>(s.data()), s.size()));
#else
p = std_fs::u8path(s); // accepts UTF-8 encoded std::string in C++17, deprecated in C++20

21
include/nlohmann/detail/conversions/to_json.hpp
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@@ -15,7 +15,8 @@
#include <algorithm> // copy
#include <iterator> // begin, end
#include <string> // string
#include <memory> // allocator_traits
#include <string> // basic_string, char_traits
#include <tuple> // tuple, get
#include <type_traits> // is_same, is_constructible, is_floating_point, is_enum, underlying_type
#include <utility> // move, forward, declval, pair
@@ -440,15 +441,21 @@ inline void to_json(BasicJsonType& j, const T& t)
}
#if JSON_HAS_FILESYSTEM || JSON_HAS_EXPERIMENTAL_FILESYSTEM
#if defined(__cpp_lib_char8_t)
template<typename BasicJsonType, typename Tr, typename Allocator>
inline void to_json(BasicJsonType& j, const std::basic_string<char8_t, Tr, Allocator>& s)
{
using OtherAllocator = typename std::allocator_traits<Allocator>::template rebind_alloc<char>;
j = std::basic_string<char, std::char_traits<char>, OtherAllocator>(s.begin(), s.end(), s.get_allocator());
}
#endif
template<typename BasicJsonType>
inline void to_json(BasicJsonType& j, const std_fs::path& p)
{
#ifdef JSON_HAS_CPP_20
const std::u8string s = p.u8string();
j = std::string(s.begin(), s.end());
#else
j = p.u8string(); // returns std::string in C++17
#endif
// Returns either a std::string or a std::u8string depending whether library
// support for char8_t is enabled.
j = p.u8string();
}
#endif

26
single_include/nlohmann/json.hpp
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@@ -5324,7 +5324,10 @@ inline void from_json(const BasicJsonType& j, std_fs::path& p)
JSON_THROW(type_error::create(302, concat("type must be string, but is ", j.type_name()), &j));
}
const auto& s = *j.template get_ptr<const typename BasicJsonType::string_t*>();
#ifdef JSON_HAS_CPP_20
// Checking for C++20 standard or later can be insufficient in case the
// library support for char8_t is either incomplete or was disabled
// altogether. Use the __cpp_lib_char8_t feature test instead.
#if defined(__cpp_lib_char8_t) && (__cpp_lib_char8_t >= 201907L)
p = std_fs::path(std::u8string_view(reinterpret_cast<const char8_t*>(s.data()), s.size()));
#else
p = std_fs::u8path(s); // accepts UTF-8 encoded std::string in C++17, deprecated in C++20
@@ -5379,7 +5382,8 @@ NLOHMANN_JSON_NAMESPACE_END
#include <algorithm> // copy
#include <iterator> // begin, end
#include <string> // string
#include <memory> // allocator_traits
#include <string> // basic_string, char_traits
#include <tuple> // tuple, get
#include <type_traits> // is_same, is_constructible, is_floating_point, is_enum, underlying_type
#include <utility> // move, forward, declval, pair
@@ -6086,15 +6090,21 @@ inline void to_json(BasicJsonType& j, const T& t)
}
#if JSON_HAS_FILESYSTEM || JSON_HAS_EXPERIMENTAL_FILESYSTEM
#if defined(__cpp_lib_char8_t)
template<typename BasicJsonType, typename Tr, typename Allocator>
inline void to_json(BasicJsonType& j, const std::basic_string<char8_t, Tr, Allocator>& s)
{
using OtherAllocator = typename std::allocator_traits<Allocator>::template rebind_alloc<char>;
j = std::basic_string<char, std::char_traits<char>, OtherAllocator>(s.begin(), s.end(), s.get_allocator());
}
#endif
template<typename BasicJsonType>
inline void to_json(BasicJsonType& j, const std_fs::path& p)
{
#ifdef JSON_HAS_CPP_20
const std::u8string s = p.u8string();
j = std::string(s.begin(), s.end());
#else
j = p.u8string(); // returns std::string in C++17
#endif
// Returns either a std::string or a std::u8string depending whether library
// support for char8_t is enabled.
j = p.u8string();
}
#endif

5
tests/src/unit-deserialization.cpp
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@@ -1134,9 +1134,10 @@ TEST_CASE("deserialization")
}
}
// select the types to test - char8_t is only available in C++20
// select the types to test - char8_t is only available since C++20 if and only
// if __cpp_char8_t is defined.
#define TYPE_LIST(...) __VA_ARGS__
#ifdef JSON_HAS_CPP_20
#if defined(__cpp_char8_t) && (__cpp_char8_t >= 201811L)
#define ASCII_TYPES TYPE_LIST(char, wchar_t, char16_t, char32_t, char8_t)
#else
#define ASCII_TYPES TYPE_LIST(char, wchar_t, char16_t, char32_t)