👷 build ci_module_cpp20 with MSVC

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

.github/workflows/ubuntu.yml

@@ -143,7 +143,7 @@ jobs:
     strategy:
       matrix:
         # older GCC docker images (4, 5, 6) fail to check out code
-        compiler: ['7', '8', '9', '10', '11', '12', '13', '14', 'latest']
+        compiler: ['7', '8', '9', '10', '11', '12', '13', '14', '15', 'latest']
     container: gcc:${{ matrix.compiler }}
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
@@ -221,6 +221,21 @@ jobs:
       - name: Build
         run: cmake --build build --target ci_cuda_example
 
+  ci_module_cpp20:
+    strategy:
+      matrix:
+        container: ['gcc:latest', 'silkeh/clang:latest']
+    runs-on: ubuntu-latest
+    container: ${{ matrix.container }}
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+      - name: Get latest CMake and ninja
+        uses: lukka/get-cmake@57c20a23a6cac5b90f31864439996e5b206df9dc # v4.0.1
+      - name: Run CMake
+        run: cmake -S . -B build -DJSON_CI=On
+      - name: Build
+        run: cmake --build build --target ci_module_cpp20
+
   ci_icpc:
     runs-on: ubuntu-latest
     container: ghcr.io/nlohmann/json-ci:v2.2.0

.github/workflows/windows.yml

@@ -111,3 +111,12 @@ jobs:
         run: cmake --build build --config Debug --parallel 10
       - name: Test
         run: cd build ; ctest -j 10 -C Debug --exclude-regex "test-unicode" --output-on-failure
+
+  ci_module_cpp20:
+    runs-on: windows-latest
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+      - name: Run CMake (Debug)
+        run: cmake -S . -B build -G "Visual Studio 17 2022" -DJSON_CI=ON -DCMAKE_CXX_FLAGS="/permissive- /std:c++latest /utf-8 /W4 /WX"
+      - name: Build
+        run: cmake --build build --config Debug --target ci_module_cpp20

cmake/ci.cmake

@@ -659,6 +659,17 @@ add_custom_target(ci_cuda_example
     COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_cuda_example
 )
 
+###############################################################################
+# C++ 20 modules
+###############################################################################
+
+add_custom_target(ci_module_cpp20
+    COMMAND ${CMAKE_COMMAND}
+        -DCMAKE_BUILD_TYPE=Debug -GNinja
+        -S${PROJECT_SOURCE_DIR}/tests/module_cpp20 -B${PROJECT_BINARY_DIR}/ci_module_cpp20
+    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/ci_module_cpp20
+)
+
 ###############################################################################
 # Intel C++ Compiler
 ###############################################################################

docs/mkdocs/docs/community/quality_assurance.md

@@ -76,6 +76,7 @@ violations will result in a failed build.
         | GNU 13.3.0                                   | x86_64       | Ubuntu 22.04.1 LTS       | GitHub    |
         | GNU 14.2.0                                   | x86_64       | Ubuntu 22.04.1 LTS       | GitHub    |
         | GNU 14.2.0                                   | arm64        | Linux 6.1.100            | Cirrus CI |
+        | GNU 15.1.0                                   | x86_64       | Ubuntu 22.04.1 LTS       | GitHub    |
         | icpc (ICC) 2021.5.0 20211109                 | x86_64       | Ubuntu 20.04.3 LTS       | GitHub    |
         | MSVC 19.0.24241.7                            | x86          | Windows 8.1              | AppVeyor  |
         | MSVC 19.16.27035.0                           | x86          | Windows-10 (Build 14393) | AppVeyor  |

include/nlohmann/detail/conversions/from_json.hpp

@@ -34,6 +34,10 @@
     #include <optional> // optional
 #endif
 
+#if JSON_HAS_FILESYSTEM || JSON_HAS_EXPERIMENTAL_FILESYSTEM
+    #include <string_view> // u8string_view
+#endif
+
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
 {

include/nlohmann/detail/input/binary_reader.hpp

@@ -53,7 +53,7 @@ enum class cbor_tag_handler_t
 
 @note from https://stackoverflow.com/a/1001328/266378
 */
-static inline bool little_endianness(int num = 1) noexcept
+inline bool little_endianness(int num = 1) noexcept
 {
     return *reinterpret_cast<char*>(&num) == 1;
 }

include/nlohmann/detail/meta/type_traits.hpp

@@ -13,7 +13,9 @@
 #include <tuple> // tuple
 #include <type_traits> // false_type, is_constructible, is_integral, is_same, true_type
 #include <utility> // declval
-
+#if defined(__cpp_lib_byte) && __cpp_lib_byte >= 201603L
+    #include <cstddef> // byte
+#endif
 #include <nlohmann/detail/iterators/iterator_traits.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
 #include <nlohmann/detail/meta/call_std/begin.hpp>
@@ -239,6 +241,30 @@ struct char_traits<signed char> : std::char_traits<char>
     }
 };
 
+#if defined(__cpp_lib_byte) && __cpp_lib_byte >= 201603L
+template<>
+struct char_traits<std::byte> : std::char_traits<char>
+{
+    using char_type = std::byte;
+    using int_type = uint64_t;
+
+    static int_type to_int_type(char_type c) noexcept
+    {
+        return static_cast<int_type>(std::to_integer<unsigned char>(c));
+    }
+
+    static char_type to_char_type(int_type i) noexcept
+    {
+        return std::byte(static_cast<unsigned char>(i));
+    }
+
+    static constexpr int_type eof() noexcept
+    {
+        return static_cast<int_type>(std::char_traits<char>::eof());
+    }
+};
+#endif
+
 ///////////////////
 // is_ functions //
 ///////////////////

include/nlohmann/detail/string_escape.hpp

@@ -62,7 +62,7 @@ inline StringType escape(StringType s)
  * Note the order of escaping "~1" to "/" and "~0" to "~" is important.
  */
 template<typename StringType>
-static void unescape(StringType& s)
+inline void unescape(StringType& s)
 {
     replace_substring(s, StringType{"~1"}, StringType{"/"});
     replace_substring(s, StringType{"~0"}, StringType{"~"});

include/nlohmann/json.hpp

@@ -39,6 +39,7 @@
 #include <nlohmann/detail/hash.hpp>
 #include <nlohmann/detail/input/binary_reader.hpp>
 #include <nlohmann/detail/input/input_adapters.hpp>
+#include <nlohmann/detail/input/json_sax.hpp>
 #include <nlohmann/detail/input/lexer.hpp>
 #include <nlohmann/detail/input/parser.hpp>
 #include <nlohmann/detail/iterators/internal_iterator.hpp>

single_include/nlohmann/json.hpp

@@ -3126,7 +3126,7 @@ inline StringType escape(StringType s)
  * Note the order of escaping "~1" to "/" and "~0" to "~" is important.
  */
 template<typename StringType>
-static void unescape(StringType& s)
+inline void unescape(StringType& s)
 {
     replace_substring(s, StringType{"~1"}, StringType{"/"});
     replace_substring(s, StringType{"~0"}, StringType{"~"});
@@ -3367,7 +3367,9 @@ NLOHMANN_JSON_NAMESPACE_END
 #include <tuple> // tuple
 #include <type_traits> // false_type, is_constructible, is_integral, is_same, true_type
 #include <utility> // declval
-
+#if defined(__cpp_lib_byte) && __cpp_lib_byte >= 201603L
+    #include <cstddef> // byte
+#endif
 // #include <nlohmann/detail/iterators/iterator_traits.hpp>
 //     __ _____ _____ _____
 //  __|  |   __|     |   | |  JSON for Modern C++
@@ -3776,6 +3778,30 @@ struct char_traits<signed char> : std::char_traits<char>
     }
 };
 
+#if defined(__cpp_lib_byte) && __cpp_lib_byte >= 201603L
+template<>
+struct char_traits<std::byte> : std::char_traits<char>
+{
+    using char_type = std::byte;
+    using int_type = uint64_t;
+
+    static int_type to_int_type(char_type c) noexcept
+    {
+        return static_cast<int_type>(std::to_integer<unsigned char>(c));
+    }
+
+    static char_type to_char_type(int_type i) noexcept
+    {
+        return std::byte(static_cast<unsigned char>(i));
+    }
+
+    static constexpr int_type eof() noexcept
+    {
+        return static_cast<int_type>(std::char_traits<char>::eof());
+    }
+};
+#endif
+
 ///////////////////
 // is_ functions //
 ///////////////////
@@ -4819,6 +4845,10 @@ NLOHMANN_JSON_NAMESPACE_END
     #include <optional> // optional
 #endif
 
+#if JSON_HAS_FILESYSTEM || JSON_HAS_EXPERIMENTAL_FILESYSTEM
+    #include <string_view> // u8string_view
+#endif
+
 NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
 {
@@ -9838,7 +9868,7 @@ enum class cbor_tag_handler_t
 
 @note from https://stackoverflow.com/a/1001328/266378
 */
-static inline bool little_endianness(int num = 1) noexcept
+inline bool little_endianness(int num = 1) noexcept
 {
     return *reinterpret_cast<char*>(&num) == 1;
 }
@@ -12859,6 +12889,8 @@ NLOHMANN_JSON_NAMESPACE_END
 
 // #include <nlohmann/detail/input/input_adapters.hpp>
 
+// #include <nlohmann/detail/input/json_sax.hpp>
+
 // #include <nlohmann/detail/input/lexer.hpp>
 
 // #include <nlohmann/detail/input/parser.hpp>

tests/module_cpp20/CMakeLists.txt

@@ -0,0 +1,12 @@
+cmake_minimum_required(VERSION 3.28)
+
+project(json_test CXX)
+
+add_executable(json_test)
+
+target_sources(json_test
+    PRIVATE main.cpp
+    PUBLIC FILE_SET cxx_modules TYPE CXX_MODULES FILES json.cpp)
+
+target_compile_features(json_test PUBLIC cxx_std_20)
+target_include_directories(json_test PRIVATE ../../include)

tests/module_cpp20/json.cpp

@@ -0,0 +1,17 @@
+module;
+#include <nlohmann/json.hpp>
+export module json;
+
+export namespace nlohmann
+{
+using ::nlohmann::adl_serializer;
+
+using ::nlohmann::basic_json;
+using ::nlohmann::json_pointer;
+
+using ::nlohmann::json;
+using ::nlohmann::ordered_json;
+using ::nlohmann::ordered_map;
+
+using ::nlohmann::json_pointer;
+}  // namespace nlohmann

tests/module_cpp20/main.cpp

@@ -0,0 +1,6 @@
+import json;
+
+int main()
+{
+    nlohmann::json j;
+}

tests/src/unit-msgpack.cpp

@@ -1880,3 +1880,82 @@ TEST_CASE("MessagePack roundtrips" * doctest::skip())
         }
     }
 }
+
+#ifdef JSON_HAS_CPP_17
+// Test suite for verifying MessagePack handling with std::byte input
+TEST_CASE("MessagePack with std::byte")
+{
+
+    SECTION("std::byte compatibility")
+    {
+        SECTION("vector roundtrip")
+        {
+            json original =
+            {
+                {"name", "test"},
+                {"value", 42},
+                {"array", {1, 2, 3}}
+            };
+
+            std::vector<uint8_t> temp = json::to_msgpack(original);
+            // Convert the uint8_t vector to std::byte vector
+            std::vector<std::byte> msgpack_data(temp.size());
+            for (size_t i = 0; i < temp.size(); ++i)
+            {
+                msgpack_data[i] = std::byte(temp[i]);
+            }
+            // Deserialize from std::byte vector back to JSON
+            json from_bytes;
+            CHECK_NOTHROW(from_bytes = json::from_msgpack(msgpack_data));
+
+            CHECK(from_bytes == original);
+        }
+
+        SECTION("empty vector")
+        {
+            const std::vector<std::byte> empty_data;
+            CHECK_THROWS_WITH_AS([&]()
+            {
+                [[maybe_unused]] auto result = json::from_msgpack(empty_data);
+                return true;
+            }
+            (),
+            "[json.exception.parse_error.110] parse error at byte 1: syntax error while parsing MessagePack value: unexpected end of input",
+            json::parse_error&);
+        }
+
+        SECTION("comparison with workaround")
+        {
+            json original =
+            {
+                {"string", "hello"},
+                {"integer", 42},
+                {"float", 3.14},
+                {"boolean", true},
+                {"null", nullptr},
+                {"array", {1, 2, 3}},
+                {"object", {{"key", "value"}}}
+            };
+
+            std::vector<uint8_t> temp = json::to_msgpack(original);
+
+            std::vector<std::byte> msgpack_data(temp.size());
+            for (size_t i = 0; i < temp.size(); ++i)
+            {
+                msgpack_data[i] = std::byte(temp[i]);
+            }
+            // Attempt direct deserialization using std::byte input
+            json direct_result = json::from_msgpack(msgpack_data);
+
+            // Test the workaround approach: reinterpret as unsigned char* and use iterator range
+            const auto* const char_start = reinterpret_cast<unsigned char const*>(msgpack_data.data());
+            const auto* const char_end = char_start + msgpack_data.size();
+            json workaround_result = json::from_msgpack(char_start, char_end);
+
+            // Verify that the final deserialized JSON matches the original JSON
+            CHECK(direct_result == workaround_result);
+            CHECK(direct_result == original);
+        }
+    }
+}
+#endif

tests/src/unit-regression2.cpp

@@ -396,7 +396,7 @@ struct Example_3810
     Example_3810() = default;
 };
 
-NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(Example_3810, bla); // NOLINT(misc-use-internal-linkage)
+NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(Example_3810, bla) // NOLINT(misc-use-internal-linkage)
 
 /////////////////////////////////////////////////////////////////////
 // for #4740

tests/src/unit-user_defined_input.cpp

@@ -60,12 +60,12 @@ TEST_CASE("Custom container member begin/end")
     {
         const char* data;
 
-        const char* begin() const
+        const char* begin() const noexcept
         {
             return data;
         }
 
-        const char* end() const
+        const char* end() const noexcept
         {
             return data + strlen(data); // NOLINT(cppcoreguidelines-pro-bounds-pointer-arithmetic)
         }