Use the with_object_t alias for the custom object key test types

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

docs/mkdocs/docs/community/roadmap.md

@@ -36,13 +36,26 @@ work items are tracked in the [GitHub milestones](https://github.com/nlohmann/js
 ## API stability
 
 Releases follow [semantic versioning](https://semver.org): a minor or patch release of version 3.x does not break code
-that uses the public API. In particular, a 3.x release does not:
+that uses the public API, unless that code opts in to a change with a macro as described [below](#version-40). In
+particular, a 3.x release does not:
 
-- change the signature of a function (its parameter types, return type, number of parameters, or the const-ness of a
-  member function);
-- remove or rename a function or class;
+- make breaking changes to the signature of a function: the types or order of its existing parameters, its return type,
+  its `noexcept` or `constexpr` specifier, or the const-ness of a member function. New parameters may be added if they
+  have a default value;
+- remove or rename a function or class, or change the template parameters of a public class template;
 - change which exceptions a function throws, or the [exception ids](../home/exceptions.md);
-- change access specifiers or default arguments.
+- change access specifiers, or change or remove existing default arguments. New default arguments may be added;
+- change the JSON type that a valid input parses to, or the text that `dump()` produces for a valid value;
+- accept input that was rejected before, or reject input that was accepted before;
+- change the order in which the keys of an object are iterated. The default type sorts keys, and
+  [`ordered_json`](../api/ordered_json.md) keeps insertion order;
+- change when iterators, pointers, or references are invalidated, or the state of a moved-from `basic_json`;
+- add or remove implicit conversions from `basic_json`;
+- change how `to_json` and `from_json` functions are found, or the behavior of
+  [`adl_serializer`](../api/adl_serializer/index.md);
+- add pure virtual functions to the [`json_sax`](../api/json_sax/index.md) interface;
+- remove, rename, renumber, or add enumerators of `value_t`;
+- remove or rename a documented macro, CMake option, CMake target, or header, or change what a documented macro does.
 
 Exceptions to these rules, for instance when fixing a bug requires changing the exception a function throws, are
 documented in the [release notes](../home/releases.md).
@@ -51,13 +64,14 @@ The following are **not** part of the public API and may change in any release,
 
 - The text of exception messages returned by `what()`. Use the [exception id](../home/exceptions.md) to tell errors
   apart.
-- The ABI, including `sizeof(basic_json)` and the memory layout of its values. Recompile your code when you upgrade the
-  library. The [versioned inline namespace](../features/namespace.md) turns mixing versions into a link error.
+- The ABI, including `sizeof(basic_json)` and the memory layout of its values. The
+  [versioned inline namespace](../features/namespace.md) turns mixing versions into a link error.
+- The hash values returned by `std::hash` for `basic_json`. Numbers that compare equal still hash equally.
 - Everything in namespace `nlohmann::detail`, and macros and type traits that are not documented in the
   [API reference](../api/basic_json/index.md).
 
-Changes that would break the public API are only added behind a macro whose default keeps the 3.x behavior, see
-[Version 4.0](#version-40).
+Breaking changes are only added behind a macro whose default keeps the 3.x behavior. See [Version 4.0](#version-40) and
+the [macro overview](../features/macros.md).
 
 ## Version 4.0
 

docs/mkdocs/docs/examples/contains__json_pointer.cpp

@@ -19,25 +19,9 @@ int main()
               << j.contains("/array/1"_json_pointer) << '\n'
               << j.contains("/array/-"_json_pointer) << '\n'
               << j.contains("/array/4"_json_pointer) << '\n'
-              << j.contains("/baz"_json_pointer) << std::endl;
-
-    try
-    {
-        // try to use an array index with leading '0'
-        j.contains("/array/01"_json_pointer);
-    }
-    catch (const json::parse_error& e)
-    {
-        std::cout << e.what() << '\n';
-    }
-
-    try
-    {
-        // try to use an array index that is not a number
-        j.contains("/array/one"_json_pointer);
-    }
-    catch (const json::parse_error& e)
-    {
-        std::cout << e.what() << '\n';
-    }
+              << j.contains("/baz"_json_pointer) << '\n'
+              // an array index with a leading '0' is not found
+              << j.contains("/array/01"_json_pointer) << '\n'
+              // an array index that is not a number is not found
+              << j.contains("/array/one"_json_pointer) << std::endl;
 }

docs/mkdocs/docs/examples/contains__json_pointer.output

@@ -5,3 +5,5 @@ true
 false
 false
 false
+false
+false

docs/mkdocs/docs/examples/parse_error.cpp

@@ -8,7 +8,7 @@ int main()
     try
     {
         // parsing input with a syntax error
-        json::parse("[1,2,3,]");
+        json j = json::parse("[1,2,3,]");
     }
     catch (const json::parse_error& e)
     {

include/nlohmann/detail/conversions/from_json.hpp

@@ -48,7 +48,7 @@ inline void from_json(const BasicJsonType& j, typename std::nullptr_t& n)
 {
     if (JSON_HEDLEY_UNLIKELY(!j.is_null()))
     {
-        throw_type_must_be("null", j);
+        JSON_THROW(type_error::create(302, concat("type must be null, but is ", j.type_name()), &j));
     }
     n = nullptr;
 }
@@ -102,7 +102,7 @@ void get_arithmetic_value(const BasicJsonType& j, ArithmeticType& val)
         case value_t::binary:
         case value_t::discarded:
         default:
-            throw_type_must_be("number", j);
+            JSON_THROW(type_error::create(302, concat("type must be number, but is ", j.type_name()), &j));
     }
 }
 
@@ -111,7 +111,7 @@ inline void from_json(const BasicJsonType& j, typename BasicJsonType::boolean_t&
 {
     if (JSON_HEDLEY_UNLIKELY(!j.is_boolean()))
     {
-        throw_type_must_be("boolean", j);
+        JSON_THROW(type_error::create(302, concat("type must be boolean, but is ", j.type_name()), &j));
     }
     b = *j.template get_ptr<const typename BasicJsonType::boolean_t*>();
 }
@@ -121,7 +121,7 @@ inline void from_json(const BasicJsonType& j, typename BasicJsonType::string_t&
 {
     if (JSON_HEDLEY_UNLIKELY(!j.is_string()))
     {
-        throw_type_must_be("string", j);
+        JSON_THROW(type_error::create(302, concat("type must be string, but is ", j.type_name()), &j));
     }
     s = *j.template get_ptr<const typename BasicJsonType::string_t*>();
 }
@@ -137,7 +137,7 @@ inline void from_json(const BasicJsonType& j, StringType& s)
 {
     if (JSON_HEDLEY_UNLIKELY(!j.is_string()))
     {
-        throw_type_must_be("string", j);
+        JSON_THROW(type_error::create(302, concat("type must be string, but is ", j.type_name()), &j));
     }
 
     s = *j.template get_ptr<const typename BasicJsonType::string_t*>();
@@ -183,7 +183,7 @@ inline void from_json(const BasicJsonType& j, std::forward_list<T, Allocator>& l
 {
     if (JSON_HEDLEY_UNLIKELY(!j.is_array()))
     {
-        throw_type_must_be("array", j);
+        JSON_THROW(type_error::create(302, concat("type must be array, but is ", j.type_name()), &j));
     }
     l.clear();
     std::transform(j.rbegin(), j.rend(),
@@ -200,7 +200,7 @@ inline void from_json(const BasicJsonType& j, std::valarray<T>& l)
 {
     if (JSON_HEDLEY_UNLIKELY(!j.is_array()))
     {
-        throw_type_must_be("array", j);
+        JSON_THROW(type_error::create(302, concat("type must be array, but is ", j.type_name()), &j));
     }
     l.resize(j.size());
     std::transform(j.begin(), j.end(), std::begin(l),
@@ -305,7 +305,7 @@ void())
 {
     if (JSON_HEDLEY_UNLIKELY(!j.is_array()))
     {
-        throw_type_must_be("array", j);
+        JSON_THROW(type_error::create(302, concat("type must be array, but is ", j.type_name()), &j));
     }
 
     from_json_array_impl(j, arr, priority_tag<3> {});
@@ -324,7 +324,7 @@ auto from_json(const BasicJsonType& j, identity_tag<std::array<T, N>> tag)
 {
     if (JSON_HEDLEY_UNLIKELY(!j.is_array()))
     {
-        throw_type_must_be("array", j);
+        JSON_THROW(type_error::create(302, concat("type must be array, but is ", j.type_name()), &j));
     }
 
     return from_json_inplace_array_impl(j, tag, make_index_sequence<N> {});
@@ -335,7 +335,7 @@ inline void from_json(const BasicJsonType& j, typename BasicJsonType::binary_t&
 {
     if (JSON_HEDLEY_UNLIKELY(!j.is_binary()))
     {
-        throw_type_must_be("binary", j);
+        JSON_THROW(type_error::create(302, concat("type must be binary, but is ", j.type_name()), &j));
     }
 
     bin = *j.template get_ptr<const typename BasicJsonType::binary_t*>();
@@ -356,7 +356,7 @@ inline void from_json(const BasicJsonType& j, CompatibleArrayType& bin)
     }
     else
     {
-        throw_type_must_be("binary or array", j);
+        JSON_THROW(type_error::create(302, concat("type must be binary or array, but is ", j.type_name()), &j));
     }
 }
 
@@ -377,7 +377,7 @@ inline void from_json(const BasicJsonType& j, ConstructibleObjectType& obj)
 {
     if (JSON_HEDLEY_UNLIKELY(!j.is_object()))
     {
-        throw_type_must_be("object", j);
+        JSON_THROW(type_error::create(302, concat("type must be object, but is ", j.type_name()), &j));
     }
 
     ConstructibleObjectType ret;
@@ -432,7 +432,7 @@ inline void from_json(const BasicJsonType& j, ArithmeticType& val)
         case value_t::binary:
         case value_t::discarded:
         default:
-            throw_type_must_be("number", j);
+            JSON_THROW(type_error::create(302, concat("type must be number, but is ", j.type_name()), &j));
     }
 }
 
@@ -504,7 +504,7 @@ auto from_json(const BasicJsonType& j, TupleRelated&& t)
 {
     if (JSON_HEDLEY_UNLIKELY(!j.is_array()))
     {
-        throw_type_must_be("array", j);
+        JSON_THROW(type_error::create(302, concat("type must be array, but is ", j.type_name()), &j));
     }
 
     return from_json_tuple_impl(j, std::forward<TupleRelated>(t), priority_tag<3> {});
@@ -517,14 +517,14 @@ void from_json_pair_array_to_map(const BasicJsonType& j, MapType& m)
 {
     if (JSON_HEDLEY_UNLIKELY(!j.is_array()))
     {
-        throw_type_must_be("array", j);
+        JSON_THROW(type_error::create(302, concat("type must be array, but is ", j.type_name()), &j));
     }
     m.clear();
     for (const auto& p : j)
     {
         if (JSON_HEDLEY_UNLIKELY(!p.is_array()))
         {
-            throw_type_must_be("array", p);
+            JSON_THROW(type_error::create(302, concat("type must be array, but is ", p.type_name()), &p));
         }
         m.emplace(p.at(0).template get<typename MapType::key_type>(), p.at(1).template get<typename MapType::mapped_type>());
     }
@@ -591,7 +591,7 @@ inline void from_json(const BasicJsonType& j, std_fs::path& p)
 {
     if (JSON_HEDLEY_UNLIKELY(!j.is_string()))
     {
-        throw_type_must_be("string", j);
+        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*>();
     // Checking for C++20 standard or later can be insufficient in case the

include/nlohmann/detail/conversions/to_json.hpp

@@ -414,13 +414,13 @@ inline void to_json(BasicJsonType& j, const EnumKeyedMap& map)
         BasicJsonType key = p.first;
         if (JSON_HEDLEY_UNLIKELY(!key.is_string()))
         {
-            throw_type_must_be("string", key);
+            JSON_THROW(type_error::create(302, concat("type must be string, but is ", key.type_name()), &key));
         }
 
         auto& key_string = *key.template get_ptr<typename BasicJsonType::string_t*>();
         if (JSON_HEDLEY_UNLIKELY(!obj.emplace(key_string, BasicJsonType(p.second)).second))
         {
-            JSON_THROW(type_error::create(exception_id::enum_key_duplicate, concat("duplicate object key '", key_string, "'"), &key));
+            JSON_THROW(type_error::create(318, concat("duplicate object key '", key_string, "'"), &key));
         }
     }
     external_constructor<value_t::object>::construct(j, std::move(obj));

include/nlohmann/detail/exceptions.hpp

@@ -45,84 +45,6 @@ namespace detail
 // exceptions //
 ////////////////
 
-/*!
-@brief the ids of the exceptions thrown by the library
-@note The values are part of the public API: they are the `id` member of the
-      exceptions and appear in their `what()` messages.
-@sa https://json.nlohmann.me/home/exceptions/
-*/
-enum class exception_id : int
-{
-    // parse_error
-    syntax_error = 101, ///< unexpected token or invalid literal while parsing JSON
-    patch_not_an_array = 104, ///< a JSON Patch document is not an array of objects
-    patch_invalid_operation = 105, ///< a JSON Patch operation is malformed
-    pointer_index_leading_zero = 106, ///< a JSON Pointer array index has a leading zero
-    pointer_missing_slash = 107, ///< a JSON Pointer does not start with '/'
-    pointer_invalid_escape = 108, ///< a JSON Pointer contains an escape other than ~0 and ~1
-    pointer_index_not_a_number = 109, ///< a JSON Pointer array index is not a number
-    unexpected_end_of_input = 110, ///< a binary input ends early, or has bytes left at its end
-    unexpected_byte = 112, ///< a binary input contains an unexpected byte or invalid length
-    invalid_string_or_size = 113, ///< a binary input contains an invalid string or size specification
-    bson_unsupported_type = 114, ///< a BSON record type is not supported
-    invalid_high_precision_number = 115, ///< a UBJSON/BJData high-precision number cannot be parsed
-    // invalid_iterator
-    iterators_incompatible = 201, ///< the iterators of a range belong to different values
-    iterator_from_other_value = 202, ///< an iterator does not belong to the value it is used with
-    iterator_range_from_other_value = 203, ///< an iterator range does not belong to the value it is used with
-    iterator_range_out_of_range = 204, ///< an iterator range of a primitive value is not [begin, end)
-    iterator_out_of_range = 205, ///< an iterator of a primitive value is not begin()
-    iterator_range_of_null = 206, ///< an iterator range belongs to a null value
-    iterator_key_not_object = 207, ///< key() is called on an iterator of a non-object
-    iterator_subscript_on_object = 208, ///< operator[] is called on an iterator of an object
-    iterator_arithmetic_on_object = 209, ///< an offset operator is used on an iterator of an object
-    insert_range_incompatible = 210, ///< the iterators of an inserted range belong to different values
-    insert_range_into_itself = 211, ///< an inserted range belongs to the value it is inserted into
-    iterators_compare_different_values = 212, ///< iterators of different values are compared
-    iterator_order_on_object = 213, ///< iterators of an object are compared by order
-    iterator_value_unavailable = 214, ///< an iterator does not refer to a value
-    // type_error
-    object_from_non_pairs = 301, ///< an object is created from an initializer list that is not a list of pairs
-    type_mismatch = 302, ///< a value has the wrong type for a conversion
-    incompatible_reference_type = 303, ///< get_ref() is called with a reference type that does not match the value
-    at_wrong_type = 304, ///< at() is called on a value of the wrong type
-    subscript_wrong_type = 305, ///< operator[] is called on a value of the wrong type
-    value_wrong_type = 306, ///< value() is called on a value of the wrong type
-    erase_wrong_type = 307, ///< erase() is called on a value of the wrong type
-    push_back_wrong_type = 308, ///< push_back() or operator+= is called on a value of the wrong type
-    insert_wrong_type = 309, ///< insert() is called on a value of the wrong type
-    swap_wrong_type = 310, ///< swap() is called on a value of the wrong type
-    emplace_wrong_type = 311, ///< emplace() or emplace_back() is called on a value of the wrong type
-    update_wrong_type = 312, ///< update() is called on a value of the wrong type
-    unflatten_invalid_value = 313, ///< unflatten() finds conflicting paths
-    unflatten_not_object = 314, ///< unflatten() is called on a non-object
-    unflatten_value_not_primitive = 315, ///< unflatten() is called on an object with non-primitive values
-    invalid_utf8 = 316, ///< dump() finds a string that is not valid UTF-8
-    type_not_serializable = 317, ///< a value cannot be serialized to the requested binary format
-    enum_key_duplicate = 318, ///< an enum-keyed map has two keys that serialize to the same string
-    discarded_value_used = 321, ///< a discarded value is used
-    // out_of_range
-    array_index_out_of_range = 401, ///< an array index is out of range
-    pointer_past_the_end_index = 402, ///< a JSON Pointer uses the array index '-'
-    key_not_found = 403, ///< an object key is not found
-    pointer_unresolved = 404, ///< a JSON Pointer reference token cannot be resolved
-    patch_on_root = 405, ///< the root of a value has no parent, e.g. for a JSON Patch 'remove' or 'add' at the root
-    number_overflow = 406, ///< a number cannot be stored without overflowing to NaN or INF
-    integer_too_large = 407, ///< an integer cannot be represented in the binary format
-    container_too_large = 408, ///< the size of a container in a binary input exceeds the maximal capacity
-    bson_key_with_null = 409, ///< a BSON key contains U+0000
-    value_out_of_range = 410, ///< an enum value is undefined, or a JSON Pointer array index exceeds size_type
-    patch_add_parent_not_container = 411, ///< the parent of a JSON Patch 'add' target is not a container
-    length_too_large = 412, ///< a length does not fit into the length field of a binary format
-    patch_remove_parent_not_container = 413, ///< the parent of a JSON Patch 'remove' target is not a container
-    patch_move_into_child = 414, ///< a JSON Patch 'move' moves a value into one of its children
-    subtype_out_of_range = 415, ///< a binary subtype does not fit into one byte
-    // other_error
-    internal_error = 500, ///< unreachable code was reached
-    patch_test_failed = 501, ///< a JSON Patch 'test' operation failed
-    size_marker_required = 502  ///< UBJSON/BJData output with type markers requires size markers
-};
-
 /// @brief general exception of the @ref basic_json class
 /// @sa https://json.nlohmann.me/api/basic_json/exception/
 class exception : public std::exception
@@ -273,18 +195,6 @@ class parse_error : public exception
         return {id_, byte_, w.c_str()};
     }
 
-    template<typename BasicJsonContext, enable_if_t<is_basic_json_context<BasicJsonContext>::value, int> = 0>
-    static parse_error create(exception_id id_, const position_t& pos, const std::string& what_arg, BasicJsonContext context)
-    {
-        return create(static_cast<int>(id_), pos, what_arg, context);
-    }
-
-    template<typename BasicJsonContext, enable_if_t<is_basic_json_context<BasicJsonContext>::value, int> = 0>
-    static parse_error create(exception_id id_, std::size_t byte_, const std::string& what_arg, BasicJsonContext context)
-    {
-        return create(static_cast<int>(id_), byte_, what_arg, context);
-    }
-
     /*!
     @brief byte index of the parse error
 
@@ -319,12 +229,6 @@ class invalid_iterator : public exception
         return {id_, w.c_str()};
     }
 
-    template<typename BasicJsonContext, enable_if_t<is_basic_json_context<BasicJsonContext>::value, int> = 0>
-    static invalid_iterator create(exception_id id_, const std::string& what_arg, BasicJsonContext context)
-    {
-        return create(static_cast<int>(id_), what_arg, context);
-    }
-
   private:
     JSON_HEDLEY_NON_NULL(3)
     invalid_iterator(int id_, const char* what_arg)
@@ -343,12 +247,6 @@ class type_error : public exception
         return {id_, w.c_str()};
     }
 
-    template<typename BasicJsonContext, enable_if_t<is_basic_json_context<BasicJsonContext>::value, int> = 0>
-    static type_error create(exception_id id_, const std::string& what_arg, BasicJsonContext context)
-    {
-        return create(static_cast<int>(id_), what_arg, context);
-    }
-
   private:
     JSON_HEDLEY_NON_NULL(3)
     type_error(int id_, const char* what_arg) : exception(id_, what_arg) {}
@@ -366,12 +264,6 @@ class out_of_range : public exception
         return {id_, w.c_str()};
     }
 
-    template<typename BasicJsonContext, enable_if_t<is_basic_json_context<BasicJsonContext>::value, int> = 0>
-    static out_of_range create(exception_id id_, const std::string& what_arg, BasicJsonContext context)
-    {
-        return create(static_cast<int>(id_), what_arg, context);
-    }
-
   private:
     JSON_HEDLEY_NON_NULL(3)
     out_of_range(int id_, const char* what_arg) : exception(id_, what_arg) {}
@@ -389,12 +281,6 @@ class other_error : public exception
         return {id_, w.c_str()};
     }
 
-    template<typename BasicJsonContext, enable_if_t<is_basic_json_context<BasicJsonContext>::value, int> = 0>
-    static other_error create(exception_id id_, const std::string& what_arg, BasicJsonContext context)
-    {
-        return create(static_cast<int>(id_), what_arg, context);
-    }
-
   private:
     JSON_HEDLEY_NON_NULL(3)
     other_error(int id_, const char* what_arg) : exception(id_, what_arg) {}
@@ -421,36 +307,6 @@ void templated_json_throw(ExceptionType exception)
     (void)exception;
 }
 
-/*!
-@brief throws because @a j does not have the type a conversion expects
-@param[in] expected  the expected type(s), e.g. "array" or "binary or array"
-@param[in] j         the value with the wrong type
-@throw type_error.302 always
-*/
-template<typename BasicJsonType>
-JSON_HEDLEY_NO_RETURN inline void throw_type_must_be(const char* expected, const BasicJsonType& j)
-{
-    static_cast<void>(expected); // unused when JSON_NOEXCEPTION is defined
-    static_cast<void>(j);
-    JSON_THROW(type_error::create(exception_id::type_mismatch, concat("type must be ", expected, ", but is ", j.type_name()), &j));
-}
-
-/*!
-@brief throws because an operation is not supported for the type of @a j
-@param[in] id_        the id of the type_error exception (at_wrong_type..update_wrong_type)
-@param[in] operation  the operation, e.g. "erase()"
-@param[in] j          the value the operation was called on
-@throw type_error always
-*/
-template<typename BasicJsonType>
-JSON_HEDLEY_NO_RETURN inline void throw_cannot_use_with(const exception_id id_, const char* operation, const BasicJsonType& j)
-{
-    static_cast<void>(id_); // unused when JSON_NOEXCEPTION is defined
-    static_cast<void>(operation);
-    static_cast<void>(j);
-    JSON_THROW(type_error::create(id_, concat("cannot use ", operation, " with ", j.type_name()), &j));
-}
-
 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END
 

include/nlohmann/detail/input/binary_reader.hpp

@@ -12,6 +12,7 @@
 #include <cmath> // ldexp
 #include <cstddef> // size_t
 #include <cstdint> // uint8_t, uint16_t, uint32_t, uint64_t, uintmax_t
+#include <cstdio> // snprintf
 #include <cstring> // memcpy
 #include <iterator> // back_inserter
 #include <limits> // numeric_limits
@@ -195,7 +196,8 @@ class binary_reader
 
             if (JSON_HEDLEY_UNLIKELY(current != char_traits<char_type>::eof()))
             {
-                return last_byte_error(exception_id::unexpected_end_of_input, concat("expected end of input; last byte: 0x", get_token_string()), "value");
+                return sax->parse_error(chars_read, get_token_string(), parse_error::create(110, chars_read,
+                                        exception_message(concat("expected end of input; last byte: 0x", get_token_string()), "value"), nullptr));
             }
         }
 
@@ -317,7 +319,8 @@ class binary_reader
     {
         if (JSON_HEDLEY_UNLIKELY(document_size < 0 || static_cast<std::size_t>(document_size) != chars_read - document_start))
         {
-            return last_byte_error(exception_id::unexpected_byte, concat("document size ", std::to_string(document_size), " does not match the number of bytes read (", std::to_string(chars_read - document_start), ")"), "document");
+            return sax->parse_error(chars_read, get_token_string(), parse_error::create(112, chars_read,
+                                    exception_message(concat("document size ", std::to_string(document_size), " does not match the number of bytes read (", std::to_string(chars_read - document_start), ")"), "document"), nullptr));
         }
         return true;
     }
@@ -509,7 +512,9 @@ class binary_reader
     {
         if (JSON_HEDLEY_UNLIKELY(len < 1))
         {
-            return last_byte_error(exception_id::unexpected_byte, concat("string length must be at least 1, is ", std::to_string(len)), "string");
+            auto last_token = get_token_string();
+            return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
+                                    exception_message(concat("string length must be at least 1, is ", std::to_string(len)), "string"), nullptr));
         }
 
         if (JSON_HEDLEY_UNLIKELY(!get_string(len - static_cast<NumberType>(1), result)))
@@ -519,7 +524,10 @@ class binary_reader
 
         if (JSON_HEDLEY_UNLIKELY(get() != 0x00))
         {
-            return last_byte_error(exception_id::unexpected_byte, "BSON string is not null-terminated", "string");
+            auto last_token = get_token_string();
+            return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
+                                    exception_message("BSON string is not null-terminated",
+                                            "string"), nullptr));
         }
 
         return check_string_utf8(result, "string");
@@ -539,7 +547,9 @@ class binary_reader
     {
         if (JSON_HEDLEY_UNLIKELY(len < 0))
         {
-            return last_byte_error(exception_id::unexpected_byte, concat("byte array length cannot be negative, is ", std::to_string(len)), "binary");
+            auto last_token = get_token_string();
+            return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
+                                    exception_message(concat("byte array length cannot be negative, is ", std::to_string(len)), "binary"), nullptr));
         }
 
         // All BSON binary values have a subtype
@@ -629,9 +639,11 @@ class binary_reader
 
             default: // anything else is not supported (yet)
             {
-                const std::string cr_str = hex_byte(static_cast<std::uint8_t>(element_type));
+                std::array<char, 3> cr{{}};
+                static_cast<void>((std::snprintf)(cr.data(), cr.size(), "%.2hhX", static_cast<unsigned char>(element_type))); // NOLINT(cppcoreguidelines-pro-type-vararg,hicpp-vararg)
+                const std::string cr_str{cr.data()};
                 return sax->parse_error(element_type_parse_position, cr_str,
-                                        parse_error::create(exception_id::bson_unsupported_type, element_type_parse_position, concat("Unsupported BSON record type 0x", cr_str), nullptr));
+                                        parse_error::create(114, element_type_parse_position, concat("Unsupported BSON record type 0x", cr_str), nullptr));
             }
         }
     }
@@ -955,7 +967,9 @@ class binary_reader
             {
                 if (tag_handler == cbor_tag_handler_t::error)
                 {
-                    return invalid_byte("value");
+                    auto last_token = get_token_string();
+                    return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
+                                            exception_message(concat("invalid byte: 0x", last_token), "value"), nullptr));
                 }
 
                 // ignore and store: the tag value is already in the head, so
@@ -975,7 +989,9 @@ class binary_reader
                 {
                     case cbor_tag_handler_t::error:
                     {
-                        return invalid_byte("value");
+                        auto last_token = get_token_string();
+                        return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
+                                                exception_message(concat("invalid byte: 0x", last_token), "value"), nullptr));
                     }
 
                     case cbor_tag_handler_t::ignore:
@@ -1049,7 +1065,9 @@ class binary_reader
 
             default: // anything else (0xFF is handled inside the other types)
             {
-                return invalid_byte("value");
+                auto last_token = get_token_string();
+                return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
+                                        exception_message(concat("invalid byte: 0x", last_token), "value"), nullptr));
             }
         }
     }
@@ -1062,7 +1080,10 @@ class binary_reader
     */
     bool cbor_indefinite_string_error(const char* type_name, const char* context)
     {
-        return last_byte_error(exception_id::invalid_string_or_size, concat("indefinite-length ", type_name, " is not allowed inside indefinite-length ", type_name, "; last byte: 0x", get_token_string()), context);
+        auto last_token = get_token_string();
+        return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read,
+                                exception_message(concat("indefinite-length ", type_name,
+                                        " is not allowed inside indefinite-length ", type_name, "; last byte: 0x", last_token), context), nullptr));
     }
 
     /*!
@@ -1139,7 +1160,9 @@ class binary_reader
 
             default:
             {
-                return last_byte_error(exception_id::invalid_string_or_size, concat("expected length specification (0x60-0x7B)", inside_indefinite ? "" : " or indefinite string type (0x7F)", "; last byte: 0x", get_token_string()), "string");
+                auto last_token = get_token_string();
+                return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read,
+                                        exception_message(concat("expected length specification (0x60-0x7B)", inside_indefinite ? "" : " or indefinite string type (0x7F)", "; last byte: 0x", last_token), "string"), nullptr));
             }
         }
     }
@@ -1269,7 +1292,9 @@ class binary_reader
                 break;
         }
 
-        return last_byte_error(exception_id::invalid_string_or_size, concat("only string keys are supported, but found ", found, "; last byte: 0x", get_token_string()), "object key");
+        auto last_token = get_token_string();
+        return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read,
+                                exception_message(concat("only string keys are supported, but found ", found, "; last byte: 0x", last_token), "object key"), nullptr));
     }
 
     /*!
@@ -1350,7 +1375,9 @@ class binary_reader
 
             default:
             {
-                return last_byte_error(exception_id::invalid_string_or_size, concat("expected length specification (0x40-0x5B)", inside_indefinite ? "" : " or indefinite binary array type (0x5F)", "; last byte: 0x", get_token_string()), "binary");
+                auto last_token = get_token_string();
+                return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read,
+                                        exception_message(concat("expected length specification (0x40-0x5B)", inside_indefinite ? "" : " or indefinite binary array type (0x5F)", "; last byte: 0x", last_token), "binary"), nullptr));
             }
         }
     }
@@ -1496,7 +1523,7 @@ class binary_reader
     {
         if (JSON_HEDLEY_UNLIKELY(!value_in_range_of<std::size_t>(len) || len == detail::unknown_size()))
         {
-            return sax->parse_error(chars_read, get_token_string(), out_of_range::create(exception_id::container_too_large,
+            return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408,
                                     exception_message(concat("excessive ", context, " size"), "size"), nullptr));
         }
         result = conditional_static_cast<std::size_t>(len);
@@ -1984,7 +2011,9 @@ class binary_reader
 
             default: // anything else
             {
-                return invalid_byte("value");
+                auto last_token = get_token_string();
+                return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
+                                        exception_message(concat("invalid byte: 0x", last_token), "value"), nullptr));
             }
         }
     }
@@ -2065,7 +2094,9 @@ class binary_reader
 
             default:
             {
-                return last_byte_error(exception_id::invalid_string_or_size, concat("expected length specification (0xA0-0xBF, 0xD9-0xDB); last byte: 0x", get_token_string()), "string");
+                auto last_token = get_token_string();
+                return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read,
+                                        exception_message(concat("expected length specification (0xA0-0xBF, 0xD9-0xDB); last byte: 0x", last_token), "string"), nullptr));
             }
         }
     }
@@ -2157,7 +2188,9 @@ class binary_reader
                 break;
         }
 
-        return last_byte_error(exception_id::invalid_string_or_size, concat("only string keys are supported, but found ", found, "; last byte: 0x", get_token_string()), "object key");
+        auto last_token = get_token_string();
+        return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read,
+                                exception_message(concat("only string keys are supported, but found ", found, "; last byte: 0x", last_token), "object key"), nullptr));
     }
 
     /*!
@@ -2466,7 +2499,8 @@ class binary_reader
     {
         if (JSON_HEDLEY_UNLIKELY(len < 0))
         {
-            return last_byte_error(exception_id::invalid_string_or_size, "string length must not be negative", "string");
+            return sax->parse_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
+                                    exception_message("string length must not be negative", "string"), nullptr));
         }
         return true;
     }
@@ -2566,7 +2600,18 @@ class binary_reader
             default:
                 break;
         }
-        return length_type_error("", "string");
+        auto last_token = get_token_string();
+        std::string message;
+
+        if (input_format != input_format_t::bjdata)
+        {
+            message = "expected length type specification (U, i, I, l, L); last byte: 0x" + last_token;
+        }
+        else
+        {
+            message = "expected length type specification (U, i, u, I, m, l, M, L); last byte: 0x" + last_token;
+        }
+        return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read, exception_message(message, "string"), nullptr));
     }
 
     /*!
@@ -2651,11 +2696,12 @@ class binary_reader
         }
         if (JSON_HEDLEY_UNLIKELY(number < 0))
         {
-            return last_byte_error(exception_id::invalid_string_or_size, "count in an optimized container must be positive", "size");
+            return sax->parse_error(chars_read, get_token_string(), parse_error::create(113, chars_read,
+                                    exception_message("count in an optimized container must be positive", "size"), nullptr));
         }
         if (JSON_HEDLEY_UNLIKELY(!value_in_range_of<std::size_t>(number)))
         {
-            return sax->parse_error(chars_read, get_token_string(), out_of_range::create(exception_id::container_too_large,
+            return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408,
                                     exception_message("integer value overflow", "size"), nullptr));
         }
         result = static_cast<std::size_t>(number); // NOLINT(bugprone-signed-char-misuse,cert-str34-c): number is not a char
@@ -2753,7 +2799,7 @@ class binary_reader
                 }
                 if (!value_in_range_of<std::size_t>(number))
                 {
-                    return sax->parse_error(chars_read, get_token_string(), out_of_range::create(exception_id::container_too_large,
+                    return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408,
                                             exception_message("integer value overflow", "size"), nullptr));
                 }
                 result = detail::conditional_static_cast<std::size_t>(number);
@@ -2768,7 +2814,7 @@ class binary_reader
                 }
                 if (is_ndarray) // ndarray dimensional vector can only contain integers and cannot embed another array
                 {
-                    return last_byte_error(exception_id::invalid_string_or_size, "ndarray dimensional vector is not allowed", "size");
+                    return sax->parse_error(chars_read, get_token_string(), parse_error::create(113, chars_read, exception_message("ndarray dimensional vector is not allowed", "size"), nullptr));
                 }
                 std::vector<size_t> dim;
                 if (JSON_HEDLEY_UNLIKELY(!get_ubjson_ndarray_size(dim)))
@@ -2804,7 +2850,9 @@ class binary_reader
                         const char* type_name = bjd_type_name(ndarray_dtype);
                         if (JSON_HEDLEY_UNLIKELY(type_name == nullptr))
                         {
-                            return invalid_byte("type");
+                            auto last_token = get_token_string();
+                            return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
+                                                    exception_message("invalid byte: 0x" + last_token, "type"), nullptr));
                         }
 
                         string_t type_key = "_ArrayType_";
@@ -2832,7 +2880,7 @@ class binary_reader
                         // or SIZE_MAX.
                         if (JSON_HEDLEY_UNLIKELY(result > (std::numeric_limits<std::size_t>::max)() / i))
                         {
-                            return sax->parse_error(chars_read, get_token_string(), out_of_range::create(exception_id::container_too_large, exception_message("excessive ndarray size caused overflow", "size"), nullptr));
+                            return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408, exception_message("excessive ndarray size caused overflow", "size"), nullptr));
                         }
                         result *= i;
                         // the pre-check above already rules out result becoming 0
@@ -2841,7 +2889,7 @@ class binary_reader
                         // unknown-size container (see get_ubjson_size_type())
                         if (result == npos)
                         {
-                            return sax->parse_error(chars_read, get_token_string(), out_of_range::create(exception_id::container_too_large, exception_message("excessive ndarray size caused overflow", "size"), nullptr));
+                            return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408, exception_message("excessive ndarray size caused overflow", "size"), nullptr));
                         }
                         if (JSON_HEDLEY_UNLIKELY(!emit_unsigned(i)))
                         {
@@ -2858,7 +2906,18 @@ class binary_reader
             default:
                 break;
         }
-        return length_type_error(" after '#'", "size");
+        auto last_token = get_token_string();
+        std::string message;
+
+        if (input_format != input_format_t::bjdata)
+        {
+            message = "expected length type specification (U, i, I, l, L) after '#'; last byte: 0x" + last_token;
+        }
+        else
+        {
+            message = "expected length type specification (U, i, u, I, m, l, M, L) after '#'; last byte: 0x" + last_token;
+        }
+        return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read, exception_message(message, "size"), nullptr));
     }
 
     /*!
@@ -2891,7 +2950,9 @@ class binary_reader
             if (input_format == input_format_t::bjdata
                     && JSON_HEDLEY_UNLIKELY(is_bjd_excluded_optimized_type(result.second)))
             {
-                return last_byte_error(exception_id::unexpected_byte, concat("marker 0x", get_token_string(), " is not a permitted optimized array type"), "type");
+                auto last_token = get_token_string();
+                return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
+                                        exception_message(concat("marker 0x", last_token, " is not a permitted optimized array type"), "type"), nullptr));
             }
 
             if (JSON_HEDLEY_UNLIKELY(!unexpect_eof("type")))
@@ -2906,7 +2967,9 @@ class binary_reader
                 {
                     return false;
                 }
-                return last_byte_error(exception_id::unexpected_byte, concat("expected '#' after type information; last byte: 0x", get_token_string()), "size");
+                auto last_token = get_token_string();
+                return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
+                                        exception_message(concat("expected '#' after type information; last byte: 0x", last_token), "size"), nullptr));
             }
 
             const bool is_error = get_ubjson_size_value(result.first, is_ndarray, 0, result.second);
@@ -2925,7 +2988,8 @@ class binary_reader
             const bool is_error = get_ubjson_size_value(result.first, is_ndarray);
             if (input_format == input_format_t::bjdata && is_ndarray && !inside_ndarray)
             {
-                return last_byte_error(exception_id::unexpected_byte, "ndarray requires both type and size", "size");
+                return sax->parse_error(chars_read, get_token_string(), parse_error::create(112, chars_read,
+                                        exception_message("ndarray requires both type and size", "size"), nullptr));
             }
             return is_error;
         }
@@ -3057,7 +3121,9 @@ class binary_reader
                 }
                 if (JSON_HEDLEY_UNLIKELY(current > 127))
                 {
-                    return last_byte_error(exception_id::invalid_string_or_size, concat("byte after 'C' must be in range 0x00..0x7F; last byte: 0x", get_token_string()), "char");
+                    auto last_token = get_token_string();
+                    return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read,
+                                            exception_message(concat("byte after 'C' must be in range 0x00..0x7F; last byte: 0x", last_token), "char"), nullptr));
                 }
                 string_t s(1, static_cast<typename string_t::value_type>(current));
                 return sax->string(s);
@@ -3078,7 +3144,8 @@ class binary_reader
             default: // anything else
                 break;
         }
-        return invalid_byte("value");
+        auto last_token = get_token_string();
+        return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read, exception_message("invalid byte: 0x" + last_token, "value"), nullptr));
     }
 
     /*!
@@ -3141,7 +3208,7 @@ class binary_reader
             if (JSON_HEDLEY_UNLIKELY((size_and_type.second == 'Z' || size_and_type.second == 'T' || size_and_type.second == 'F')
                                      && size_and_type.first > max_valueless_container_size))
             {
-                return sax->parse_error(chars_read, get_token_string(), out_of_range::create(exception_id::container_too_large,
+                return sax->parse_error(chars_read, get_token_string(), out_of_range::create(408,
                                         exception_message("excessive array size", "size"), nullptr));
             }
 
@@ -3177,7 +3244,9 @@ class binary_reader
         // do not accept ND-array size in objects in BJData
         if (input_format == input_format_t::bjdata && size_and_type.first != npos && (size_and_type.second & (1 << 8)) != 0)
         {
-            return last_byte_error(exception_id::unexpected_byte, "BJData object does not support ND-array size in optimized format", "object");
+            auto last_token = get_token_string();
+            return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
+                                    exception_message("BJData object does not support ND-array size in optimized format", "object"), nullptr));
         }
 
         if (size_and_type.first != npos)
@@ -3214,7 +3283,7 @@ class binary_reader
             // the lexer would stop at a NUL and accept the digits before it
             if (JSON_HEDLEY_UNLIKELY(current == '\0'))
             {
-                return sax->parse_error(chars_read, "00", parse_error::create(exception_id::invalid_high_precision_number, chars_read,
+                return sax->parse_error(chars_read, "00", parse_error::create(115, chars_read,
                                         exception_message("invalid number text; last byte: 0x00", "high-precision number"), nullptr));
             }
             number_vector.push_back(static_cast<char>(current));
@@ -3231,7 +3300,7 @@ class binary_reader
 
         if (JSON_HEDLEY_UNLIKELY(result_remainder != token_type::end_of_input))
         {
-            return sax->parse_error(chars_read, number_string, parse_error::create(exception_id::invalid_high_precision_number, chars_read,
+            return sax->parse_error(chars_read, number_string, parse_error::create(115, chars_read,
                                     exception_message(concat("invalid number text: ", number_lexer.get_token_string()), "high-precision number"), nullptr));
         }
 
@@ -3249,7 +3318,7 @@ class binary_reader
                     return sax->parse_error(
                                chars_read,
                                number_string,
-                               out_of_range::create(exception_id::number_overflow, concat("number overflow parsing '", number_string, '\''), nullptr));
+                               out_of_range::create(406, concat("number overflow parsing '", number_string, '\''), nullptr));
                 }
                 // number_string is a std::string, while the SAX interface takes a
                 // string_t; convert explicitly, as the two are only implicitly
@@ -3271,7 +3340,7 @@ class binary_reader
             case token_type::end_of_input:
             case token_type::literal_or_value:
             default:
-                return sax->parse_error(chars_read, number_string, parse_error::create(exception_id::invalid_high_precision_number, chars_read,
+                return sax->parse_error(chars_read, number_string, parse_error::create(115, chars_read,
                                         exception_message(concat("invalid number text: ", number_lexer.get_token_string()), "high-precision number"), nullptr));
         }
     }
@@ -3330,6 +3399,20 @@ class binary_reader
         return 0x80 <= c && c <= 0xBF;
     }
 
+    /*!
+    @brief report a parse error at the last read byte
+
+    @param[in] detail   a detailed error message
+    @param[in] context  further context information
+    @return false
+    */
+    bool bon8_error(const std::string& detail, const char* context)
+    {
+        auto last_token = get_token_string();
+        return sax->parse_error(chars_read, last_token, parse_error::create(112, chars_read,
+                                exception_message(concat(detail, ": 0x", last_token), context), nullptr));
+    }
+
     /*!
     @brief read a BON8 value and everything nested inside it
 
@@ -3545,7 +3628,7 @@ class binary_reader
         }
 
         // 0xFE: end of container where a value is expected
-        return invalid_byte("value");
+        return bon8_error("invalid byte", "value");
     }
 
     /*!
@@ -3672,7 +3755,7 @@ class binary_reader
             current = byte;
         }
 
-        return unexpected_byte("expected a string; last byte", "key");
+        return bon8_error("expected a string; last byte", "key");
     }
 
     /*!
@@ -3795,7 +3878,7 @@ class binary_reader
 
             if (JSON_HEDLEY_UNLIKELY(!valid_second))
             {
-                return unexpected_byte("invalid UTF-8 byte", "string");
+                return bon8_error("invalid UTF-8 byte", "string");
             }
 
             result.push_back(static_cast<typename string_t::value_type>(byte));
@@ -3809,7 +3892,7 @@ class binary_reader
                 }
                 if (JSON_HEDLEY_UNLIKELY(!is_bon8_continuation(current)))
                 {
-                    return unexpected_byte("invalid UTF-8 byte", "string");
+                    return bon8_error("invalid UTF-8 byte", "string");
                 }
                 result.push_back(static_cast<typename string_t::value_type>(current));
             }
@@ -3854,7 +3937,7 @@ class binary_reader
         {
             // in case of failure, advance position by 1 to report the failing location
             ++chars_read;
-            sax->parse_error(chars_read, "<end of file>", parse_error::create(exception_id::unexpected_end_of_input, chars_read, exception_message("unexpected end of input", context), nullptr));
+            sax->parse_error(chars_read, "<end of file>", parse_error::create(110, chars_read, exception_message("unexpected end of input", context), nullptr));
             return false;
         }
         return true;
@@ -4008,7 +4091,7 @@ class binary_reader
         if (JSON_HEDLEY_UNLIKELY(std::isfinite(number) && !std::isfinite(result)))
         {
             return sax->parse_error(chars_read, get_token_string(),
-                                    out_of_range::create(exception_id::number_overflow, exception_message("number overflow", "value"), nullptr));
+                                    out_of_range::create(406, exception_message("number overflow", "value"), nullptr));
         }
         return sax->number_float(result, "");
     }
@@ -4128,7 +4211,9 @@ class binary_reader
 
         if (error_handler == error_handler_t::strict)
         {
-            return last_byte_error(exception_id::invalid_string_or_size, "invalid string: ill-formed UTF-8 byte", context);
+            auto last_token = get_token_string();
+            return sax->parse_error(chars_read, last_token, parse_error::create(113, chars_read,
+                                    exception_message("invalid string: ill-formed UTF-8 byte", context), nullptr));
         }
 
         result = sanitize_utf8(result, error_handler);
@@ -4224,63 +4309,19 @@ class binary_reader
         if (JSON_HEDLEY_UNLIKELY(current == char_traits<char_type>::eof()))
         {
             return sax->parse_error(chars_read, "<end of file>",
-                                    parse_error::create(exception_id::unexpected_end_of_input, chars_read, exception_message("unexpected end of input", context), nullptr));
+                                    parse_error::create(110, chars_read, exception_message("unexpected end of input", context), nullptr));
         }
         return true;
     }
 
-    /*!
-    @brief reports a parse error at the last read byte
-    @param[in] id_      the id of the parse_error exception
-    @param[in] detail   a detailed error message
-    @param[in] context  further context information
-    @return the result of the SAX parser's parse_error()
-    */
-    bool last_byte_error(const exception_id id_, const std::string& detail, const std::string& context) const
-    {
-        return sax->parse_error(chars_read, get_token_string(), parse_error::create(id_, chars_read, exception_message(detail, context), nullptr));
-    }
-
-    /*!
-    @brief reports the last read byte as unexpected (parse_error.112)
-    @param[in] detail   what is wrong with the byte, e.g. "invalid byte"
-    @param[in] context  further context information
-    @return the result of the SAX parser's parse_error()
-    */
-    bool unexpected_byte(const char* detail, const std::string& context) const
-    {
-        return last_byte_error(exception_id::unexpected_byte, concat(detail, ": 0x", get_token_string()), context);
-    }
-
-    /*!
-    @brief reports the last read byte as invalid (parse_error.112)
-    @param[in] context  further context information
-    @return the result of the SAX parser's parse_error()
-    */
-    bool invalid_byte(const char* context) const
-    {
-        return unexpected_byte("invalid byte", context);
-    }
-
-    /*!
-    @brief reports that the last read byte is not a UBJSON/BJData length type (parse_error.113)
-    @param[in] position  where the length type was expected, e.g. " after '#'"
-    @param[in] context   further context information
-    @return the result of the SAX parser's parse_error()
-    */
-    bool length_type_error(const char* position, const char* context) const
-    {
-        const char* types = input_format == input_format_t::bjdata ? "U, i, u, I, m, l, M, L" : "U, i, I, l, L";
-        return last_byte_error(exception_id::invalid_string_or_size,
-                               concat("expected length type specification (", types, ")", position, "; last byte: 0x", get_token_string()), context);
-    }
-
     /*!
     @return a string representation of the last read byte
     */
     std::string get_token_string() const
     {
-        return hex_byte(static_cast<std::uint8_t>(current));
+        std::array<char, 3> cr{{}};
+        static_cast<void>((std::snprintf)(cr.data(), cr.size(), "%.2hhX", static_cast<unsigned char>(current))); // NOLINT(cppcoreguidelines-pro-type-vararg,hicpp-vararg)
+        return std::string{cr.data()};
     }
 
     /*!

include/nlohmann/detail/input/input_adapters.hpp

@@ -581,7 +581,7 @@ class wide_string_input_adapter
     template<class T>
     JSON_HEDLEY_NO_RETURN std::size_t get_elements(T* /*dest*/, std::size_t /*count*/ = 1)
     {
-        JSON_THROW(parse_error::create(exception_id::unexpected_byte, 1, "wide string type cannot be interpreted as binary data", nullptr));
+        JSON_THROW(parse_error::create(112, 1, "wide string type cannot be interpreted as binary data", nullptr));
     }
 
   private:
@@ -793,7 +793,7 @@ inline file_input_adapter input_adapter(std::FILE* file)
 {
     if (file == nullptr)
     {
-        JSON_THROW(parse_error::create(exception_id::syntax_error, 0, "attempting to parse an empty input; check that your input string or stream contains the expected JSON", nullptr));
+        JSON_THROW(parse_error::create(101, 0, "attempting to parse an empty input; check that your input string or stream contains the expected JSON", nullptr));
     }
     return file_input_adapter(file);
 }
@@ -802,7 +802,7 @@ inline input_stream_adapter input_adapter(std::istream& stream)
 {
     if (stream.rdbuf() == nullptr)
     {
-        JSON_THROW(parse_error::create(exception_id::syntax_error, 0, "attempting to parse an empty input; check that your input string or stream contains the expected JSON", nullptr));
+        JSON_THROW(parse_error::create(101, 0, "attempting to parse an empty input; check that your input string or stream contains the expected JSON", nullptr));
     }
     return input_stream_adapter(stream);
 }
@@ -827,7 +827,7 @@ contiguous_bytes_input_adapter input_adapter(CharT b)
 {
     if (b == nullptr)
     {
-        JSON_THROW(parse_error::create(exception_id::syntax_error, 0, "attempting to parse an empty input; check that your input string or stream contains the expected JSON", nullptr));
+        JSON_THROW(parse_error::create(101, 0, "attempting to parse an empty input; check that your input string or stream contains the expected JSON", nullptr));
     }
     auto length = std::strlen(reinterpret_cast<const char*>(b));
     const auto* ptr = reinterpret_cast<const char*>(b);

include/nlohmann/detail/input/json_sax.hpp

@@ -176,27 +176,6 @@ template<typename ArrayType>
 inline void reserve_array(ArrayType& /*arr*/, std::size_t /*len*/, priority_tag<0> /*unused*/)
 {}
 
-/*!
-@brief reports an object or array whose announced size exceeds max_size()
-
-Shared by json_sax_dom_parser and json_sax_dom_callback_parser.
-
-@param[in] sax   the SAX parser to report the error to
-@param[in] len   the number of elements announced by the input, or unknown_size()
-@param[in] kind  "object" or "array"
-@param[in] ref   the object or array that was just created
-@return whether parsing should continue (false after reporting out_of_range.408)
-*/
-template<typename SAX, typename BasicJsonType>
-bool check_container_size(SAX& sax, std::size_t len, const char* kind, BasicJsonType* ref)
-{
-    if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref->max_size()))
-    {
-        return sax.parse_error(0, "", out_of_range::create(exception_id::container_too_large, concat("excessive ", kind, " size: ", std::to_string(len)), ref));
-    }
-    return true;
-}
-
 #if JSON_DIAGNOSTIC_POSITIONS
 /*!
 @brief set the diagnostic positions of a value the DOM SAX parsers just stored
@@ -206,35 +185,6 @@ befriends this struct, as the position members are private.
 */
 struct diagnostic_positions
 {
-    /*!
-    @param[in,out] v  the object or array whose opening brace or bracket was just read
-    @param[in] lexer  the lexer that read it, or nullptr to leave @a v alone
-    */
-    template<typename BasicJsonType, typename LexerType>
-    static void set_container_start(BasicJsonType& v, LexerType* lexer)
-    {
-        if (lexer)
-        {
-            // Lexer has read the first character of the container, so
-            // subtract 1 from the position to get the correct start position.
-            v.start_position = lexer->get_position() - 1;
-        }
-    }
-
-    /*!
-    @param[in,out] v  the object or array whose closing brace or bracket was just read
-    @param[in] lexer  the lexer that read it, or nullptr to leave @a v alone
-    */
-    template<typename BasicJsonType, typename LexerType>
-    static void set_container_end(BasicJsonType& v, LexerType* lexer)
-    {
-        if (lexer)
-        {
-            // Lexer's position is past the closing brace or bracket, so set that as the end position.
-            v.end_position = lexer->get_position();
-        }
-    }
-
     /*!
     @param[in,out] v  the value that was just parsed
     @param[in] lexer  the lexer that read it, or nullptr to leave @a v alone
@@ -399,11 +349,22 @@ class json_sax_dom_parser
         ref_stack.push_back(handle_value(BasicJsonType::value_t::object));
 
 #if JSON_DIAGNOSTIC_POSITIONS
+        // Manually set the start position of the object here.
         // Ensure this is after the call to handle_value to ensure correct start position.
-        diagnostic_positions::set_container_start(*ref_stack.back(), m_lexer_ref);
+        if (m_lexer_ref)
+        {
+            // Lexer has read the first character of the object, so
+            // subtract 1 from the position to get the correct start position.
+            ref_stack.back()->start_position = m_lexer_ref->get_position() - 1;
+        }
 #endif
 
-        return check_container_size(*this, len, "object", ref_stack.back());
+        if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
+        {
+            return parse_error(0, "", out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
+        }
+
+        return true;
     }
 
     bool key(string_t& val)
@@ -422,7 +383,11 @@ class json_sax_dom_parser
         JSON_ASSERT(ref_stack.back()->is_object());
 
 #if JSON_DIAGNOSTIC_POSITIONS
-        diagnostic_positions::set_container_end(*ref_stack.back(), m_lexer_ref);
+        if (m_lexer_ref)
+        {
+            // Lexer's position is past the closing brace, so set that as the end position.
+            ref_stack.back()->end_position = m_lexer_ref->get_position();
+        }
 #endif
 
         ref_stack.back()->set_parents();
@@ -435,13 +400,17 @@ class json_sax_dom_parser
         ref_stack.push_back(handle_value(BasicJsonType::value_t::array));
 
 #if JSON_DIAGNOSTIC_POSITIONS
+        // Manually set the start position of the array here.
         // Ensure this is after the call to handle_value to ensure correct start position.
-        diagnostic_positions::set_container_start(*ref_stack.back(), m_lexer_ref);
+        if (m_lexer_ref)
+        {
+            ref_stack.back()->start_position = m_lexer_ref->get_position() - 1;
+        }
 #endif
 
-        if (JSON_HEDLEY_UNLIKELY(!check_container_size(*this, len, "array", ref_stack.back())))
+        if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
         {
-            return false;
+            return parse_error(0, "", out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
         }
 
         if (len != detail::unknown_size())
@@ -458,7 +427,11 @@ class json_sax_dom_parser
         JSON_ASSERT(ref_stack.back()->is_array());
 
 #if JSON_DIAGNOSTIC_POSITIONS
-        diagnostic_positions::set_container_end(*ref_stack.back(), m_lexer_ref);
+        if (m_lexer_ref)
+        {
+            // Lexer's position is past the closing bracket, so set that as the end position.
+            ref_stack.back()->end_position = m_lexer_ref->get_position();
+        }
 #endif
 
         ref_stack.back()->set_parents();
@@ -638,11 +611,21 @@ class json_sax_dom_callback_parser
         {
 
 #if JSON_DIAGNOSTIC_POSITIONS
+            // Manually set the start position of the object here.
             // Ensure this is after the call to handle_value to ensure correct start position.
-            diagnostic_positions::set_container_start(*ref_stack.back(), m_lexer_ref);
+            if (m_lexer_ref)
+            {
+                // Lexer has read the first character of the object, so
+                // subtract 1 from the position to get the correct start position.
+                ref_stack.back()->start_position = m_lexer_ref->get_position() - 1;
+            }
 #endif
 
-            return check_container_size(*this, len, "object", ref_stack.back());
+            // check object limit
+            if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
+            {
+                return parse_error(0, "", out_of_range::create(408, concat("excessive object size: ", std::to_string(len)), ref_stack.back()));
+            }
         }
         return true;
     }
@@ -712,7 +695,11 @@ class json_sax_dom_callback_parser
             {
 
 #if JSON_DIAGNOSTIC_POSITIONS
-                diagnostic_positions::set_container_end(*ref_stack.back(), m_lexer_ref);
+                if (m_lexer_ref)
+                {
+                    // Lexer's position is past the closing brace, so set that as the end position.
+                    ref_stack.back()->end_position = m_lexer_ref->get_position();
+                }
 #endif
 
                 ref_stack.back()->set_parents();
@@ -723,7 +710,13 @@ class json_sax_dom_callback_parser
             }
         }
 
-        const string_t object_key = pop_container();
+        JSON_ASSERT(!ref_stack.empty());
+        JSON_ASSERT(!keep_stack.empty());
+        JSON_ASSERT(!container_key_stack.empty());
+        ref_stack.pop_back();
+        keep_stack.pop_back();
+        const string_t object_key = std::move(container_key_stack.back());
+        container_key_stack.pop_back();
 
         if (!ref_stack.empty() && ref_stack.back() && ref_stack.back()->is_structured())
         {
@@ -749,13 +742,20 @@ class json_sax_dom_callback_parser
         {
 
 #if JSON_DIAGNOSTIC_POSITIONS
+            // Manually set the start position of the array here.
             // Ensure this is after the call to handle_value to ensure correct start position.
-            diagnostic_positions::set_container_start(*ref_stack.back(), m_lexer_ref);
+            if (m_lexer_ref)
+            {
+                // Lexer has read the first character of the array, so
+                // subtract 1 from the position to get the correct start position.
+                ref_stack.back()->start_position = m_lexer_ref->get_position() - 1;
+            }
 #endif
 
-            if (JSON_HEDLEY_UNLIKELY(!check_container_size(*this, len, "array", ref_stack.back())))
+            // check array limit
+            if (JSON_HEDLEY_UNLIKELY(len != detail::unknown_size() && len > ref_stack.back()->max_size()))
             {
-                return false;
+                return parse_error(0, "", out_of_range::create(408, concat("excessive array size: ", std::to_string(len)), ref_stack.back()));
             }
 
             if (len != detail::unknown_size())
@@ -779,7 +779,11 @@ class json_sax_dom_callback_parser
             {
 
 #if JSON_DIAGNOSTIC_POSITIONS
-                diagnostic_positions::set_container_end(*ref_stack.back(), m_lexer_ref);
+                if (m_lexer_ref)
+                {
+                    // Lexer's position is past the closing bracket, so set that as the end position.
+                    ref_stack.back()->end_position = m_lexer_ref->get_position();
+                }
 #endif
 
                 ref_stack.back()->set_parents();
@@ -805,7 +809,13 @@ class json_sax_dom_callback_parser
             }
         }
 
-        const string_t object_key = pop_container();
+        JSON_ASSERT(!ref_stack.empty());
+        JSON_ASSERT(!keep_stack.empty());
+        JSON_ASSERT(!container_key_stack.empty());
+        ref_stack.pop_back();
+        keep_stack.pop_back();
+        const string_t object_key = std::move(container_key_stack.back());
+        container_key_stack.pop_back();
 
         // remove discarded value
         if (!ref_stack.empty() && ref_stack.back())
@@ -892,23 +902,6 @@ class json_sax_dom_callback_parser
         return string_t{};
     }
 
-    /*!
-    @brief leave the object or array that end_object()/end_array() just closed
-    @return the key the container is stored under in its parent (see
-            container_key_stack)
-    */
-    string_t pop_container()
-    {
-        JSON_ASSERT(!ref_stack.empty());
-        JSON_ASSERT(!keep_stack.empty());
-        JSON_ASSERT(!container_key_stack.empty());
-        ref_stack.pop_back();
-        keep_stack.pop_back();
-        string_t object_key = std::move(container_key_stack.back());
-        container_key_stack.pop_back();
-        return object_key;
-    }
-
     /*!
     @brief remove the discarded value the callback rejected from its parent,
     unless it is a duplicate key's slot with a stashed previous value, in

include/nlohmann/detail/input/parser.hpp

@@ -156,7 +156,9 @@ class parser
                 // strict mode: next byte must be EOF
                 if (get_token() != token_type::end_of_input)
                 {
-                    return syntax_error(*sax, exception_message(token_type::end_of_input, "value"));
+                    return sax->parse_error(m_lexer.get_position(),
+                                            m_lexer.get_token_string(),
+                                            parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr));
                 }
             }
             else
@@ -195,7 +197,10 @@ class parser
             // in strict mode, input must be completely read
             if (get_token() != token_type::end_of_input)
             {
-                syntax_error(sdp, exception_message(token_type::end_of_input, "value"));
+                sdp.parse_error(m_lexer.get_position(),
+                                m_lexer.get_token_string(),
+                                parse_error::create(101, m_lexer.get_position(),
+                                                    exception_message(token_type::end_of_input, "value"), nullptr));
             }
         }
         else
@@ -245,7 +250,9 @@ class parser
                         // parse key
                         if (JSON_HEDLEY_UNLIKELY(last_token != token_type::value_string))
                         {
-                            return syntax_error(*sax, exception_message(token_type::value_string, "object key"));
+                            return sax->parse_error(m_lexer.get_position(),
+                                                    m_lexer.get_token_string(),
+                                                    parse_error::create(101, m_lexer.get_position(), exception_message(token_type::value_string, "object key"), nullptr));
                         }
                         if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string())))
                         {
@@ -255,7 +262,9 @@ class parser
                         // parse separator (:)
                         if (JSON_HEDLEY_UNLIKELY(!get_token_expecting(token_type::name_separator)))
                         {
-                            return syntax_error(*sax, exception_message(token_type::name_separator, "object separator"));
+                            return sax->parse_error(m_lexer.get_position(),
+                                                    m_lexer.get_token_string(),
+                                                    parse_error::create(101, m_lexer.get_position(), exception_message(token_type::name_separator, "object separator"), nullptr));
                         }
 
                         // remember we are now inside an object
@@ -298,7 +307,7 @@ class parser
                         {
                             return sax->parse_error(m_lexer.get_position(),
                                                     m_lexer.get_token_string(),
-                                                    out_of_range::create(exception_id::number_overflow, concat("number overflow parsing '", m_lexer.get_token_string(), '\''), nullptr));
+                                                    out_of_range::create(406, concat("number overflow parsing '", m_lexer.get_token_string(), '\''), nullptr));
                         }
 
                         if (JSON_HEDLEY_UNLIKELY(!sax->number_float(res, m_lexer.get_string())))
@@ -366,16 +375,23 @@ class parser
                     case token_type::parse_error:
                     {
                         // using "uninitialized" to avoid an "expected" message
-                        return syntax_error(*sax, exception_message(token_type::uninitialized, "value"));
+                        return sax->parse_error(m_lexer.get_position(),
+                                                m_lexer.get_token_string(),
+                                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::uninitialized, "value"), nullptr));
                     }
                     case token_type::end_of_input:
                     {
                         if (JSON_HEDLEY_UNLIKELY(m_lexer.get_position().chars_read_total == 1))
                         {
-                            return syntax_error(*sax, "attempting to parse an empty input; check that your input string or stream contains the expected JSON");
+                            return sax->parse_error(m_lexer.get_position(),
+                                                    m_lexer.get_token_string(),
+                                                    parse_error::create(101, m_lexer.get_position(),
+                                                            "attempting to parse an empty input; check that your input string or stream contains the expected JSON", nullptr));
                         }
 
-                        return syntax_error(*sax, exception_message(token_type::literal_or_value, "value"));
+                        return sax->parse_error(m_lexer.get_position(),
+                                                m_lexer.get_token_string(),
+                                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::literal_or_value, "value"), nullptr));
                     }
                     case token_type::uninitialized:
                     case token_type::end_array:
@@ -385,7 +401,9 @@ class parser
                     case token_type::literal_or_value:
                     default: // the last token was unexpected
                     {
-                        return syntax_error(*sax, exception_message(token_type::literal_or_value, "value"));
+                        return sax->parse_error(m_lexer.get_position(),
+                                                m_lexer.get_token_string(),
+                                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::literal_or_value, "value"), nullptr));
                     }
                 }
             }
@@ -436,7 +454,9 @@ class parser
                     continue;
                 }
 
-                return syntax_error(*sax, exception_message(token_type::end_array, "array"));
+                return sax->parse_error(m_lexer.get_position(),
+                                        m_lexer.get_token_string(),
+                                        parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_array, "array"), nullptr));
             }
 
             // states.back() is false -> object
@@ -453,7 +473,9 @@ class parser
                     // parse key
                     if (JSON_HEDLEY_UNLIKELY(last_token != token_type::value_string))
                     {
-                        return syntax_error(*sax, exception_message(token_type::value_string, "object key"));
+                        return sax->parse_error(m_lexer.get_position(),
+                                                m_lexer.get_token_string(),
+                                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::value_string, "object key"), nullptr));
                     }
 
                     if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string())))
@@ -464,7 +486,9 @@ class parser
                     // parse separator (:)
                     if (JSON_HEDLEY_UNLIKELY(!get_token_expecting(token_type::name_separator)))
                     {
-                        return syntax_error(*sax, exception_message(token_type::name_separator, "object separator"));
+                        return sax->parse_error(m_lexer.get_position(),
+                                                m_lexer.get_token_string(),
+                                                parse_error::create(101, m_lexer.get_position(), exception_message(token_type::name_separator, "object separator"), nullptr));
                     }
 
                     // parse values
@@ -492,7 +516,9 @@ class parser
                 continue;
             }
 
-            return syntax_error(*sax, exception_message(token_type::end_object, "object"));
+            return sax->parse_error(m_lexer.get_position(),
+                                    m_lexer.get_token_string(),
+                                    parse_error::create(101, m_lexer.get_position(), exception_message(token_type::end_object, "object"), nullptr));
         }
     }
 
@@ -509,21 +535,6 @@ class parser
         return (last_token = m_lexer.scan_expecting(expected_type)) == expected_type;
     }
 
-    /*!
-    @brief reports a syntax error at the current token (parse_error.101)
-    @param[in] sax      the SAX parser to report the error to
-    @param[in] message  the error message
-    @return the result of the SAX parser's parse_error()
-    */
-    template<typename SAX>
-    bool syntax_error(SAX& sax, const std::string& message)
-    {
-        // MSVC 2015 reports C4100 (unreferenced parameter) when SAX::parse_error is static
-        static_cast<void>(sax);
-        return sax.parse_error(m_lexer.get_position(), m_lexer.get_token_string(),
-                               parse_error::create(exception_id::syntax_error, m_lexer.get_position(), message, nullptr));
-    }
-
     std::string exception_message(const token_type expected, const std::string& context)
     {
         std::string error_msg = "syntax error ";

include/nlohmann/detail/iterators/iter_impl.hpp

@@ -279,12 +279,6 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
         }
     }
 
-    /// @throw invalid_iterator.214 always
-    JSON_HEDLEY_NO_RETURN void throw_cannot_get_value() const
-    {
-        JSON_THROW(invalid_iterator::create(exception_id::iterator_value_unavailable, "cannot get value", m_object));
-    }
-
   public:
     /*!
     @brief return a reference to the value pointed to by the iterator
@@ -309,7 +303,7 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
             }
 
             case value_t::null:
-                throw_cannot_get_value();
+                JSON_THROW(invalid_iterator::create(214, "cannot get value", m_object));
 
             case value_t::string:
             case value_t::boolean:
@@ -325,7 +319,7 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
                     return *m_object;
                 }
 
-                throw_cannot_get_value();
+                JSON_THROW(invalid_iterator::create(214, "cannot get value", m_object));
             }
         }
     }
@@ -367,7 +361,7 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
                     return m_object;
                 }
 
-                throw_cannot_get_value();
+                JSON_THROW(invalid_iterator::create(214, "cannot get value", m_object));
             }
         }
     }
@@ -484,7 +478,7 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
         // if objects are not the same, the comparison is undefined
         if (JSON_HEDLEY_UNLIKELY(m_object != other.m_object))
         {
-            JSON_THROW(invalid_iterator::create(exception_id::iterators_compare_different_values, "cannot compare iterators of different containers", m_object));
+            JSON_THROW(invalid_iterator::create(212, "cannot compare iterators of different containers", m_object));
         }
 
         // value-initialized forward iterators can be compared, and must compare equal to other value-initialized iterators of the same type #4493
@@ -533,7 +527,7 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
         // if objects are not the same, the comparison is undefined
         if (JSON_HEDLEY_UNLIKELY(m_object != other.m_object))
         {
-            JSON_THROW(invalid_iterator::create(exception_id::iterators_compare_different_values, "cannot compare iterators of different containers", m_object));
+            JSON_THROW(invalid_iterator::create(212, "cannot compare iterators of different containers", m_object));
         }
 
         // value-initialized forward iterators can be compared, and must compare equal to other value-initialized iterators of the same type #4493
@@ -546,7 +540,7 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
         switch (m_object->m_data.m_type)
         {
             case value_t::object:
-                JSON_THROW(invalid_iterator::create(exception_id::iterator_order_on_object, "cannot compare order of object iterators", m_object));
+                JSON_THROW(invalid_iterator::create(213, "cannot compare order of object iterators", m_object));
 
             case value_t::array:
                 return (m_it.array_iterator < other.m_it.array_iterator);
@@ -602,7 +596,7 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
         switch (m_object->m_data.m_type)
         {
             case value_t::object:
-                JSON_THROW(invalid_iterator::create(exception_id::iterator_arithmetic_on_object, "cannot use offsets with object iterators", m_object));
+                JSON_THROW(invalid_iterator::create(209, "cannot use offsets with object iterators", m_object));
 
             case value_t::array:
             {
@@ -681,7 +675,7 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
         switch (m_object->m_data.m_type)
         {
             case value_t::object:
-                JSON_THROW(invalid_iterator::create(exception_id::iterator_arithmetic_on_object, "cannot use offsets with object iterators", m_object));
+                JSON_THROW(invalid_iterator::create(209, "cannot use offsets with object iterators", m_object));
 
             case value_t::array:
                 return m_it.array_iterator - other.m_it.array_iterator;
@@ -710,13 +704,13 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
         switch (m_object->m_data.m_type)
         {
             case value_t::object:
-                JSON_THROW(invalid_iterator::create(exception_id::iterator_subscript_on_object, "cannot use operator[] for object iterators", m_object));
+                JSON_THROW(invalid_iterator::create(208, "cannot use operator[] for object iterators", m_object));
 
             case value_t::array:
                 return *std::next(m_it.array_iterator, n);
 
             case value_t::null:
-                throw_cannot_get_value();
+                JSON_THROW(invalid_iterator::create(214, "cannot get value", m_object));
 
             case value_t::string:
             case value_t::boolean:
@@ -732,7 +726,7 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
                     return *m_object;
                 }
 
-                throw_cannot_get_value();
+                JSON_THROW(invalid_iterator::create(214, "cannot get value", m_object));
             }
         }
     }
@@ -750,7 +744,7 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
             return m_it.object_iterator->first;
         }
 
-        JSON_THROW(invalid_iterator::create(exception_id::iterator_key_not_object, "cannot use key() for non-object iterators", m_object));
+        JSON_THROW(invalid_iterator::create(207, "cannot use key() for non-object iterators", m_object));
     }
 
     /*!

include/nlohmann/detail/json_pointer.hpp

@@ -166,7 +166,7 @@ class json_pointer
     {
         if (JSON_HEDLEY_UNLIKELY(empty()))
         {
-            throw_no_parent();
+            JSON_THROW(detail::out_of_range::create(405, "JSON pointer has no parent", nullptr));
         }
 
         reference_tokens.erase(reference_tokens.begin());
@@ -178,7 +178,7 @@ class json_pointer
     {
         if (JSON_HEDLEY_UNLIKELY(empty()))
         {
-            throw_no_parent();
+            JSON_THROW(detail::out_of_range::create(405, "JSON pointer has no parent", nullptr));
         }
 
         return reference_tokens.front();
@@ -204,7 +204,7 @@ class json_pointer
     {
         if (JSON_HEDLEY_UNLIKELY(empty()))
         {
-            throw_no_parent();
+            JSON_THROW(detail::out_of_range::create(405, "JSON pointer has no parent", nullptr));
         }
 
         reference_tokens.pop_back();
@@ -216,7 +216,7 @@ class json_pointer
     {
         if (JSON_HEDLEY_UNLIKELY(empty()))
         {
-            throw_no_parent();
+            JSON_THROW(detail::out_of_range::create(405, "JSON pointer has no parent", nullptr));
         }
 
         return reference_tokens.back();
@@ -244,21 +244,6 @@ class json_pointer
     }
 
   private:
-    /// @throw out_of_range.405 always
-    JSON_HEDLEY_NO_RETURN static void throw_no_parent()
-    {
-        JSON_THROW(detail::out_of_range::create(detail::exception_id::patch_on_root, "JSON pointer has no parent", nullptr));
-    }
-
-    /// @throw out_of_range.404 always
-    template<typename BasicJsonContext>
-    JSON_HEDLEY_NO_RETURN static void throw_unresolved(const string_t& reference_token, BasicJsonContext context)
-    {
-        static_cast<void>(reference_token); // unused when JSON_NOEXCEPTION is defined
-        static_cast<void>(context);
-        JSON_THROW(detail::out_of_range::create(detail::exception_id::pointer_unresolved, detail::concat("unresolved reference token '", reference_token, "'"), context));
-    }
-
     /*!
     @brief result of @ref parse_array_index
 
@@ -344,13 +329,13 @@ class json_pointer
             // the branches differ in their messages, not after JSON_THROW's expansion
             // NOLINTNEXTLINE(bugprone-branch-clone)
             case array_index_status::leading_zero:
-                JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_index_leading_zero, 0, detail::concat("array index '", s, "' must not begin with '0'"), nullptr));
+                JSON_THROW(detail::parse_error::create(106, 0, detail::concat("array index '", s, "' must not begin with '0'"), nullptr));
             case array_index_status::not_a_number:
-                JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_index_not_a_number, 0, detail::concat("array index '", s, "' is not a number"), nullptr));
+                JSON_THROW(detail::parse_error::create(109, 0, detail::concat("array index '", s, "' is not a number"), nullptr));
             case array_index_status::unresolved:
-                throw_unresolved(s, nullptr);
+                JSON_THROW(detail::out_of_range::create(404, detail::concat("unresolved reference token '", s, "'"), nullptr));
             case array_index_status::exceeds_size_type:
-                JSON_THROW(detail::out_of_range::create(detail::exception_id::value_out_of_range, detail::concat("array index ", s, " exceeds size_type"), nullptr));
+                JSON_THROW(detail::out_of_range::create(410, detail::concat("array index ", s, " exceeds size_type"), nullptr));
             case array_index_status::ok:
             default:
                 break;
@@ -364,7 +349,7 @@ class json_pointer
     {
         if (JSON_HEDLEY_UNLIKELY(empty()))
         {
-            throw_no_parent();
+            JSON_THROW(detail::out_of_range::create(405, "JSON pointer has no parent", nullptr));
         }
 
         json_pointer result = *this;
@@ -452,7 +437,7 @@ class json_pointer
                 case detail::value_t::binary:
                 case detail::value_t::discarded:
                 default:
-                    JSON_THROW(detail::type_error::create(detail::exception_id::unflatten_invalid_value, "invalid value to unflatten", &j));
+                    JSON_THROW(detail::type_error::create(313, "invalid value to unflatten", &j));
             }
 
             prefix.push_back(reference_token);
@@ -535,7 +520,7 @@ class json_pointer
                 case detail::value_t::binary:
                 case detail::value_t::discarded:
                 default:
-                    throw_unresolved(reference_token, ptr);
+                    JSON_THROW(detail::out_of_range::create(404, detail::concat("unresolved reference token '", reference_token, "'"), ptr));
             }
         }
 
@@ -567,7 +552,7 @@ class json_pointer
                     if (JSON_HEDLEY_UNLIKELY(reference_token == "-"))
                     {
                         // "-" always fails the range check
-                        JSON_THROW(detail::out_of_range::create(detail::exception_id::pointer_past_the_end_index, detail::concat(
+                        JSON_THROW(detail::out_of_range::create(402, detail::concat(
                                 "array index '-' (", std::to_string(ptr->m_data.m_value.array->size()),
                                 ") is out of range"), ptr));
                     }
@@ -576,7 +561,7 @@ class json_pointer
                     // Bounds check before access to avoid exception with JSON_NOEXCEPTION
                     if (JSON_HEDLEY_UNLIKELY(idx >= ptr->m_data.m_value.array->size()))
                     {
-                        JSON_THROW(detail::out_of_range::create(detail::exception_id::array_index_out_of_range, detail::concat(
+                        JSON_THROW(detail::out_of_range::create(401, detail::concat(
                                 "array index ", std::to_string(idx), " is out of range"), ptr));
                     }
                     ptr = &ptr->operator[](idx);
@@ -592,7 +577,7 @@ class json_pointer
                 case detail::value_t::binary:
                 case detail::value_t::discarded:
                 default:
-                    throw_unresolved(reference_token, ptr);
+                    JSON_THROW(detail::out_of_range::create(404, detail::concat("unresolved reference token '", reference_token, "'"), ptr));
             }
         }
 
@@ -636,7 +621,7 @@ class json_pointer
                     if (JSON_HEDLEY_UNLIKELY(reference_token == "-"))
                     {
                         // "-" cannot be used for const access
-                        JSON_THROW(detail::out_of_range::create(detail::exception_id::pointer_past_the_end_index, detail::concat("array index '-' (", std::to_string(ptr->m_data.m_value.array->size()), ") is out of range"), ptr));
+                        JSON_THROW(detail::out_of_range::create(402, detail::concat("array index '-' (", std::to_string(ptr->m_data.m_value.array->size()), ") is out of range"), ptr));
                     }
 
                     // use unchecked array access; the const operator[]
@@ -654,7 +639,7 @@ class json_pointer
                 case detail::value_t::binary:
                 case detail::value_t::discarded:
                 default:
-                    throw_unresolved(reference_token, ptr);
+                    JSON_THROW(detail::out_of_range::create(404, detail::concat("unresolved reference token '", reference_token, "'"), ptr));
             }
         }
 
@@ -709,9 +694,9 @@ class json_pointer
                         // the branches differ in their messages, not after JSON_THROW's expansion
                         // NOLINTNEXTLINE(bugprone-branch-clone)
                         case array_index_status::leading_zero:
-                            JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_index_leading_zero, 0, detail::concat("array index '", reference_token, "' must not begin with '0'"), nullptr));
+                            JSON_THROW(detail::parse_error::create(106, 0, detail::concat("array index '", reference_token, "' must not begin with '0'"), nullptr));
                         case array_index_status::not_a_number:
-                            JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_index_not_a_number, 0, detail::concat("array index '", reference_token, "' is not a number"), nullptr));
+                            JSON_THROW(detail::parse_error::create(109, 0, detail::concat("array index '", reference_token, "' is not a number"), nullptr));
                         case array_index_status::unresolved:
                         case array_index_status::exceeds_size_type:
                             return nullptr;
@@ -838,7 +823,7 @@ class json_pointer
         // check if a nonempty reference string begins with slash
         if (JSON_HEDLEY_UNLIKELY(reference_string[0] != '/'))
         {
-            JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_missing_slash, 1, detail::concat("JSON pointer must be empty or begin with '/' - was: '", reference_string, "'"), nullptr));
+            JSON_THROW(detail::parse_error::create(107, 1, detail::concat("JSON pointer must be empty or begin with '/' - was: '", reference_string, "'"), nullptr));
         }
 
         // extract the reference tokens:
@@ -874,7 +859,7 @@ class json_pointer
                                          (reference_token[pos + 1] != '0' &&
                                           reference_token[pos + 1] != '1')))
                 {
-                    JSON_THROW(detail::parse_error::create(detail::exception_id::pointer_invalid_escape, 0, "escape character '~' must be followed with '0' or '1'", nullptr));
+                    JSON_THROW(detail::parse_error::create(108, 0, "escape character '~' must be followed with '0' or '1'", nullptr));
                 }
             }
 
@@ -971,7 +956,7 @@ class json_pointer
     {
         if (JSON_HEDLEY_UNLIKELY(!value.is_object()))
         {
-            JSON_THROW(detail::type_error::create(detail::exception_id::unflatten_not_object, "only objects can be unflattened", &value));
+            JSON_THROW(detail::type_error::create(314, "only objects can be unflattened", &value));
         }
 
         BasicJsonType result;
@@ -999,7 +984,7 @@ class json_pointer
         {
             if (JSON_HEDLEY_UNLIKELY(!element.second.is_primitive()))
             {
-                JSON_THROW(detail::type_error::create(detail::exception_id::unflatten_value_not_primitive, "values in object must be primitive", &element.second));
+                JSON_THROW(detail::type_error::create(315, "values in object must be primitive", &element.second));
             }
 
             // Assign the value to the reference pointed to by JSON pointer. Note

include/nlohmann/detail/macro_scope.hpp

@@ -312,7 +312,7 @@
             return ej_pair.first == e;                                                          \
         });                                                                                     \
         if (it != std::end(m)) j = it->second;                                                  \
-        else ::nlohmann::detail::templated_json_throw<nlohmann::detail::out_of_range>(nlohmann::detail::out_of_range::create(nlohmann::detail::exception_id::value_out_of_range,"enum value out of range for " #ENUM_TYPE, nullptr)); \
+        else ::nlohmann::detail::templated_json_throw<nlohmann::detail::out_of_range>(nlohmann::detail::out_of_range::create(410,"enum value out of range for " #ENUM_TYPE, nullptr)); \
     }                                                                                           \
     template<typename BasicJsonType>                                                            \
     inline void from_json(const BasicJsonType& j, ENUM_TYPE& e)                                 \
@@ -327,7 +327,7 @@
             return ej_pair.second == j;                                                         \
         });                                                                                     \
         if (it != std::end(m)) e = it->first;                                                   \
-        else ::nlohmann::detail::templated_json_throw<nlohmann::detail::out_of_range>(nlohmann::detail::out_of_range::create(nlohmann::detail::exception_id::value_out_of_range, nlohmann::detail::concat("enum value out of range for " #ENUM_TYPE ": ", j.dump(-1, ' ', false, nlohmann::detail::error_handler_t::replace)), &j)); \
+        else ::nlohmann::detail::templated_json_throw<nlohmann::detail::out_of_range>(nlohmann::detail::out_of_range::create(410, nlohmann::detail::concat("enum value out of range for " #ENUM_TYPE ": ", j.dump(-1, ' ', false, nlohmann::detail::error_handler_t::replace)), &j)); \
     }
 
 // Ugly macros to avoid uglier copy-paste when specializing basic_json. They

include/nlohmann/detail/meta/type_traits.hpp

@@ -172,6 +172,10 @@ struct has_to_json < BasicJsonType, T, enable_if_t < !is_basic_json<T>::value >>
 template<typename T>
 using detect_key_compare = typename T::key_compare;
 
+// detects whether two values of type T can be compared with operator==
+template<typename T>
+using detect_equal_comparable = decltype(static_cast<bool>(std::declval<const T&>() == std::declval<const T&>()));
+
 // obtains the actual object key comparator: object_t::key_compare if the
 // object type defines it, and default_object_comparator_t otherwise
 //

include/nlohmann/detail/output/binary_writer.hpp

@@ -151,7 +151,7 @@ class binary_writer
             case value_t::discarded:
             default:
             {
-                JSON_THROW(type_error::create(exception_id::type_not_serializable, concat("to serialize to BSON, top-level type must be object, but is ", j.type_name()), &j));
+                JSON_THROW(type_error::create(317, concat("to serialize to BSON, top-level type must be object, but is ", j.type_name()), &j));
             }
         }
     }
@@ -244,16 +244,7 @@ class binary_writer
 
             case value_t::string:
             {
-                string_t storage;
-                const string_t& value = sanitize_utf8_for_write(*j.m_data.m_value.string, j, storage);
-
-                // step 1: write control byte and the string length
-                write_cbor_head(0x60, value.size());
-
-                // step 2: write the string
-                oa.write_characters(
-                      reinterpret_cast<const CharType*>(value.data()),
-                      value.size());
+                write_cbor_string(*j.m_data.m_value.string, j);
                 break;
             }
 
@@ -321,18 +312,9 @@ class binary_writer
 
                 for (const auto& el : *j.m_data.m_value.object)
                 {
-                    // el.first is checked here, against the object as
-                    // diagnostics context, because write_cbor(el.first)
-                    // converts it to a temporary basic_json that would be
-                    // used as the context instead; for error_handler_t::keep
-                    // and ::replace/::ignore the recursive write_cbor(el.first)
-                    // call below handles the key like any other string, so no
-                    // separate check is needed here for those
-                    if (error_handler == error_handler_t::strict)
-                    {
-                        check_utf8(el.first, j);
-                    }
-                    write_cbor(el.first);
+                    // el.first is written directly (not via a temporary
+                    // basic_json), with the object as diagnostics context
+                    write_cbor_key(el.first, j);
                     write_cbor(el.second, depth + 1);
                 }
                 break;
@@ -354,7 +336,7 @@ class binary_writer
     {
         if (JSON_HEDLEY_UNLIKELY(!value_in_range_of<std::uint32_t>(length)))
         {
-            JSON_THROW(out_of_range::create(exception_id::length_too_large, concat("MessagePack length ", std::to_string(length), " exceeds maximum of ", std::to_string((std::numeric_limits<std::uint32_t>::max)())), &j));
+            JSON_THROW(out_of_range::create(412, concat("MessagePack length ", std::to_string(length), " exceeds maximum of ", std::to_string((std::numeric_limits<std::uint32_t>::max)())), &j));
         }
 
         static_cast<void>(j);
@@ -491,39 +473,7 @@ class binary_writer
 
             case value_t::string:
             {
-                string_t storage;
-                const string_t& value = sanitize_utf8_for_write(*j.m_data.m_value.string, j, storage);
-
-                // step 1: write control byte and the string length
-                const auto N = to_msgpack_length(value.size(), j);
-                if (N <= 31)
-                {
-                    // fixstr
-                    write_number(static_cast<std::uint8_t>(0xA0 | N));
-                }
-                else if (N <= (std::numeric_limits<std::uint8_t>::max)())
-                {
-                    // str 8
-                    oa.write_character(to_char_type(0xD9));
-                    write_number(static_cast<std::uint8_t>(N));
-                }
-                else if (N <= (std::numeric_limits<std::uint16_t>::max)())
-                {
-                    // str 16
-                    oa.write_character(to_char_type(0xDA));
-                    write_number(static_cast<std::uint16_t>(N));
-                }
-                else
-                {
-                    // str 32
-                    oa.write_character(to_char_type(0xDB));
-                    write_number(static_cast<std::uint32_t>(N));
-                }
-
-                // step 2: write the string
-                oa.write_characters(
-                      reinterpret_cast<const CharType*>(value.data()),
-                      value.size());
+                write_msgpack_string(*j.m_data.m_value.string, j);
                 break;
             }
 
@@ -613,7 +563,7 @@ class binary_writer
                 {
                     if (JSON_HEDLEY_UNLIKELY(j.m_data.m_value.binary->subtype() > (std::numeric_limits<std::uint8_t>::max)()))
                     {
-                        JSON_THROW(out_of_range::create(exception_id::subtype_out_of_range, concat("subtype ", std::to_string(j.m_data.m_value.binary->subtype()), " is too large for the MessagePack ext type (max 255)"), &j));
+                        JSON_THROW(out_of_range::create(415, concat("subtype ", std::to_string(j.m_data.m_value.binary->subtype()), " is too large for the MessagePack ext type (max 255)"), &j));
                     }
 
                     write_number(static_cast<std::int8_t>(j.m_data.m_value.binary->subtype()));
@@ -634,14 +584,9 @@ class binary_writer
 
                 for (const auto& el : *j.m_data.m_value.object)
                 {
-                    // as in write_cbor, el.first is checked here against the
-                    // object as diagnostics context; the recursive call below
-                    // handles keep/replace/ignore like any other string
-                    if (error_handler == error_handler_t::strict)
-                    {
-                        check_utf8(el.first, j);
-                    }
-                    write_msgpack(el.first);
+                    // as in write_cbor, el.first is written directly with the
+                    // object as diagnostics context
+                    write_msgpack_key(el.first, j);
                     write_msgpack(el.second, depth + 1);
                 }
                 break;
@@ -767,7 +712,7 @@ class binary_writer
                 {
                     if (!use_count)
                     {
-                        JSON_THROW(other_error::create(exception_id::size_marker_required, "use_type requires use_size = true", &j));
+                        JSON_THROW(other_error::create(502, "use_type requires use_size = true", &j));
                     }
                     oa.write_character(to_char_type('$'));
                     oa.write_character(bjdata_draft3 ? 'B' : 'U');
@@ -866,7 +811,7 @@ class binary_writer
     {
         static_cast<void>(j); // unused when JSON_NOEXCEPTION is defined
         static_cast<void>(format_name);
-        JSON_THROW(type_error::create(exception_id::discarded_value_used, concat("cannot serialize discarded value to ", format_name), &j));
+        JSON_THROW(type_error::create(321, concat("cannot serialize discarded value to ", format_name), &j));
     }
 
     void write_msgpack_array_prefix(const std::size_t N, const BasicJsonType& j)
@@ -1025,13 +970,9 @@ class binary_writer
                     continue;
                 }
 
-                // el.first is checked here, against the object as diagnostics
-                // context, like the matching check in write_cbor's object case
-                if (error_handler == error_handler_t::strict)
-                {
-                    check_utf8(current.object_it->first, *current.value);
-                }
-                write_cbor(current.object_it->first);
+                // the key is written directly (not via a temporary basic_json),
+                // with the object as diagnostics context, as in write_cbor
+                write_cbor_key(current.object_it->first, *current.value);
                 const BasicJsonType* child = &(current.object_it->second);
                 ++stack.back().object_it;
                 write_cbor_value_or_push(*child, stack);
@@ -1106,11 +1047,9 @@ class binary_writer
                     continue;
                 }
 
-                if (error_handler == error_handler_t::strict)
-                {
-                    check_utf8(current.object_it->first, *current.value);
-                }
-                write_msgpack(current.object_it->first);
+                // as in write_cbor_iterative, the key is written directly with
+                // the object as diagnostics context
+                write_msgpack_key(current.object_it->first, *current.value);
                 const BasicJsonType* child = &(current.object_it->second);
                 ++stack.back().object_it;
                 write_msgpack_value_or_push(*child, stack);
@@ -1132,7 +1071,7 @@ class binary_writer
         {
             if (!use_count)
             {
-                JSON_THROW(other_error::create(exception_id::size_marker_required, "use_type requires use_size = true", &j));
+                JSON_THROW(other_error::create(502, "use_type requires use_size = true", &j));
             }
             const CharType first_prefix = ubjson_prefix(j.front(), use_bjdata);
             const bool same_prefix = std::all_of(j.begin() + 1, j.end(),
@@ -1182,7 +1121,7 @@ class binary_writer
         {
             if (!use_count)
             {
-                JSON_THROW(other_error::create(exception_id::size_marker_required, "use_type requires use_size = true", &j));
+                JSON_THROW(other_error::create(502, "use_type requires use_size = true", &j));
             }
             const CharType first_prefix = ubjson_prefix(j.front(), use_bjdata);
             const bool same_prefix = std::all_of(j.begin(), j.end(),
@@ -1397,7 +1336,7 @@ class binary_writer
         const auto it = name.find(static_cast<typename string_t::value_type>(0));
         if (JSON_HEDLEY_UNLIKELY(it != BasicJsonType::string_t::npos))
         {
-            JSON_THROW(out_of_range::create(exception_id::bson_key_with_null, concat("BSON key cannot contain code point U+0000 (at byte ", std::to_string(it), ")"), &j));
+            JSON_THROW(out_of_range::create(409, concat("BSON key cannot contain code point U+0000 (at byte ", std::to_string(it), ")"), &j));
         }
 
         string_t storage;
@@ -1415,7 +1354,7 @@ class binary_writer
     {
         if (JSON_HEDLEY_UNLIKELY(!value_in_range_of<std::int32_t>(size)))
         {
-            JSON_THROW(out_of_range::create(exception_id::length_too_large, concat("BSON length ", std::to_string(size), " exceeds maximum of ", std::to_string((std::numeric_limits<std::int32_t>::max)())), nullptr));
+            JSON_THROW(out_of_range::create(412, concat("BSON length ", std::to_string(size), " exceeds maximum of ", std::to_string((std::numeric_limits<std::int32_t>::max)())), nullptr));
         }
 
         return static_cast<std::int32_t>(size);
@@ -1601,7 +1540,7 @@ class binary_writer
 
         if (value.has_subtype() && JSON_HEDLEY_UNLIKELY(value.subtype() > (std::numeric_limits<std::uint8_t>::max)()))
         {
-            JSON_THROW(out_of_range::create(exception_id::subtype_out_of_range, concat("subtype ", std::to_string(value.subtype()), " is too large for the BSON binary subtype (max 255)"), &j));
+            JSON_THROW(out_of_range::create(415, concat("subtype ", std::to_string(value.subtype()), " is too large for the BSON binary subtype (max 255)"), &j));
         }
 
         return sizeof(std::int32_t) + value.size() + 1ul;
@@ -1877,7 +1816,6 @@ class binary_writer
         {
             // write entries until the current object or array is done, or an
             // entry is an object or array itself
-            const string_t* nested_name = nullptr;
             const BasicJsonType* nested = nullptr;
             if (current.value->is_object())
             {
@@ -1888,7 +1826,8 @@ class binary_writer
                     ++current.member;
                     if (el.second.is_structured())
                     {
-                        nested_name = &el.first;
+                        write_bson_entry_header(el.first, el.second.is_object() ? 0x03 : 0x04);
+                        write_number<std::int32_t>(to_bson_length(nested_sizes[next_size++]), true);
                         nested = &el.second;
                     }
                     else
@@ -1907,7 +1846,8 @@ class binary_writer
                     ++current.index;
                     if (el.is_structured())
                     {
-                        nested_name = &index_name;
+                        write_bson_entry_header(index_name, el.is_object() ? 0x03 : 0x04);
+                        write_number<std::int32_t>(to_bson_length(nested_sizes[next_size++]), true);
                         nested = &el;
                     }
                     else
@@ -1919,8 +1859,6 @@ class binary_writer
 
             if (nested != nullptr)
             {
-                write_bson_entry_header(*nested_name, nested->is_object() ? 0x03 : 0x04);
-                write_number<std::int32_t>(to_bson_length(nested_sizes[next_size++]), true);
                 parents.push_back(std::move(current));
                 current = bson_frame(nested);
                 continue;
@@ -1988,6 +1926,122 @@ class binary_writer
         }
     }
 
+    /*!
+    @brief write an object key as a CBOR text string
+
+    A key convertible to string_t is written directly. Other key types (only
+    an explicit conversion, or only a to_json overload) go through a temporary
+    basic_json, as in version 3.12.0; the temporary is then the diagnostics
+    context for strict UTF-8 checks.
+    */
+    template<typename Key = typename BasicJsonType::object_t::key_type,
+             enable_if_t<std::is_convertible<Key, string_t>::value, int> = 0>
+    void write_cbor_key(const typename BasicJsonType::object_t::key_type& key, const BasicJsonType& context)
+    {
+        write_cbor_string(key, context);
+    }
+
+    template < typename Key = typename BasicJsonType::object_t::key_type,
+               enable_if_t < !std::is_convertible<Key, string_t>::value, int > = 0 >
+    void write_cbor_key(const typename BasicJsonType::object_t::key_type& key, const BasicJsonType& /*context*/)
+    {
+        write_cbor(BasicJsonType(key));
+    }
+
+    /// @brief write an object key as a MessagePack str, as in @ref write_cbor_key
+    template<typename Key = typename BasicJsonType::object_t::key_type,
+             enable_if_t<std::is_convertible<Key, string_t>::value, int> = 0>
+    void write_msgpack_key(const typename BasicJsonType::object_t::key_type& key, const BasicJsonType& context)
+    {
+        write_msgpack_string(key, context);
+    }
+
+    template < typename Key = typename BasicJsonType::object_t::key_type,
+               enable_if_t < !std::is_convertible<Key, string_t>::value, int > = 0 >
+    void write_msgpack_key(const typename BasicJsonType::object_t::key_type& key, const BasicJsonType& /*context*/)
+    {
+        write_msgpack(BasicJsonType(key));
+    }
+
+    /*!
+    @brief write a CBOR text string
+
+    @a value is checked or sanitized according to @ref error_handler, with
+    @a context (the string value itself, or the object a key belongs to) used
+    as diagnostics context; this avoids converting object keys to a temporary
+    basic_json just to write them
+
+    @note When object_t::key_type is not string_t, @a value is a temporary
+          string_t converted from the key, which lives only until the end of
+          the caller's statement. The reference returned by
+          @ref sanitize_utf8_for_write may refer to it, so it must not escape
+          this function.
+    */
+    void write_cbor_string(const string_t& value, const BasicJsonType& context)
+    {
+        string_t storage;
+        const string_t& sanitized = sanitize_utf8_for_write(value, context, storage);
+
+        // step 1: write control byte and the string length
+        write_cbor_head(0x60, sanitized.size());
+
+        // step 2: write the string
+        oa.write_characters(
+              reinterpret_cast<const CharType*>(sanitized.data()),
+              sanitized.size());
+    }
+
+    /////////////
+    // MsgPack //
+    /////////////
+
+    /*!
+    @brief write a MessagePack str
+
+    @a value is checked or sanitized according to @ref error_handler, with
+    @a context used as diagnostics context, as in @ref write_cbor_string
+
+    @note As in @ref write_cbor_string, @a value may be a temporary string_t
+          converted from a key, so the reference returned by
+          @ref sanitize_utf8_for_write must not escape this function.
+    */
+    void write_msgpack_string(const string_t& value, const BasicJsonType& context)
+    {
+        string_t storage;
+        const string_t& sanitized = sanitize_utf8_for_write(value, context, storage);
+
+        // step 1: write control byte and the string length
+        const auto N = to_msgpack_length(sanitized.size(), context);
+        if (N <= 31)
+        {
+            // fixstr
+            write_number(static_cast<std::uint8_t>(0xA0 | N));
+        }
+        else if (N <= (std::numeric_limits<std::uint8_t>::max)())
+        {
+            // str 8
+            oa.write_character(to_char_type(0xD9));
+            write_number(static_cast<std::uint8_t>(N));
+        }
+        else if (N <= (std::numeric_limits<std::uint16_t>::max)())
+        {
+            // str 16
+            oa.write_character(to_char_type(0xDA));
+            write_number(static_cast<std::uint16_t>(N));
+        }
+        else
+        {
+            // str 32
+            oa.write_character(to_char_type(0xDB));
+            write_number(static_cast<std::uint32_t>(N));
+        }
+
+        // step 2: write the string
+        oa.write_characters(
+              reinterpret_cast<const CharType*>(sanitized.data()),
+              sanitized.size());
+    }
+
     ////////////
     // UBJSON //
     ////////////
@@ -2551,7 +2605,7 @@ class binary_writer
             {
                 if (j.m_data.m_value.number_unsigned > static_cast<typename BasicJsonType::number_unsigned_t>((std::numeric_limits<std::int64_t>::max)()))
                 {
-                    JSON_THROW(out_of_range::create(exception_id::integer_too_large, concat("integer number ", std::to_string(j.m_data.m_value.number_unsigned), " cannot be represented by BON8 as it does not fit int64"), &j));
+                    JSON_THROW(out_of_range::create(407, concat("integer number ", std::to_string(j.m_data.m_value.number_unsigned), " cannot be represented by BON8 as it does not fit int64"), &j));
                 }
                 write_bon8_integer(static_cast<std::int64_t>(j.m_data.m_value.number_unsigned));
                 string_open = false;
@@ -2704,7 +2758,7 @@ class binary_writer
         const std::size_t valid = valid_utf8_prefix(data, s.size());
         if (JSON_HEDLEY_UNLIKELY(valid != s.size()))
         {
-            JSON_THROW(type_error::create(exception_id::invalid_utf8, concat("invalid UTF-8 byte at index ", std::to_string(valid), ": 0x", detail::hex_byte(data[valid])), &context));
+            JSON_THROW(type_error::create(316, concat("invalid UTF-8 byte at index ", std::to_string(valid), ": 0x", detail::hex_byte(data[valid])), &context));
         }
     }
 

include/nlohmann/detail/output/serializer.hpp

@@ -888,7 +888,7 @@ class serializer
                     {
                         case error_handler_t::strict:
                         {
-                            JSON_THROW(type_error::create(exception_id::invalid_utf8, concat("invalid UTF-8 byte at index ", std::to_string(i), ": 0x", detail::hex_byte(byte)), nullptr));
+                            JSON_THROW(type_error::create(316, concat("invalid UTF-8 byte at index ", std::to_string(i), ": 0x", detail::hex_byte(byte)), nullptr));
                         }
 
                         case error_handler_t::ignore:
@@ -1021,7 +1021,7 @@ class serializer
             {
                 case error_handler_t::strict:
                 {
-                    JSON_THROW(type_error::create(exception_id::invalid_utf8, concat("incomplete UTF-8 string; last byte: 0x", detail::hex_byte(static_cast<std::uint8_t>(s[s.size() - 1]))), nullptr));
+                    JSON_THROW(type_error::create(316, concat("incomplete UTF-8 string; last byte: 0x", detail::hex_byte(static_cast<std::uint8_t>(s[s.size() - 1]))), nullptr));
                 }
 
                 case error_handler_t::ignore:

include/nlohmann/json.hpp

@@ -639,7 +639,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                     object = nullptr;  // silence warning, see #821
                     if (JSON_HEDLEY_UNLIKELY(t == value_t::null))
                     {
-                        JSON_THROW(other_error::create(detail::exception_id::internal_error, "961c151d2e87f2686a955a9be24d316f1362bf21 3.12.0", nullptr)); // LCOV_EXCL_LINE
+                        JSON_THROW(other_error::create(500, "961c151d2e87f2686a955a9be24d316f1362bf21 3.12.0", nullptr)); // LCOV_EXCL_LINE
                     }
                     break;
                 }
@@ -1421,6 +1421,24 @@ public:
         return create<object_t>(first, last);
     }
 
+    /// @brief compare two object keys for equality, if the key type supports it
+    /// @note object_t only needs operator< for its keys (std::map), so operator==
+    ///       may not exist; the keys are then reported as different, which makes
+    ///       copy_object_level pair the values via object_t::find()
+    template<typename K = typename object_t::key_type,
+             detail::enable_if_t<detail::is_detected<detail::detect_equal_comparable, K>::value, int> = 0>
+    static bool copy_keys_equal(const K& a, const K& b)
+    {
+        return a == b;
+    }
+
+    template < typename K = typename object_t::key_type,
+               detail::enable_if_t < !detail::is_detected<detail::detect_equal_comparable, K>::value, int > = 0 >
+    static bool copy_keys_equal(const K& /*a*/, const K& /*b*/)
+    {
+        return false;
+    }
+
     /// @brief create the copy of the object @a src in @a dst
     /// @note structured values are appended to @a worklist instead
     static void copy_object_level(const basic_json& src, basic_json& dst,
@@ -1453,7 +1471,7 @@ public:
         auto src_it = src_object.cbegin();
         for (auto& element : *dst.m_data.m_value.object)
         {
-            if (JSON_HEDLEY_LIKELY(src_it != src_object.cend() && src_it->first == element.first))
+            if (JSON_HEDLEY_LIKELY(src_it != src_object.cend() && copy_keys_equal(src_it->first, element.first)))
             {
                 copy_shallow(src_it->second, element.second, worklist);
                 ++src_it;
@@ -2287,7 +2305,7 @@ public:
             // if an object is wanted but impossible, throw an exception
             if (JSON_HEDLEY_UNLIKELY(manual_type == value_t::object && !is_an_object))
             {
-                JSON_THROW(type_error::create(detail::exception_id::object_from_non_pairs, "cannot create object from initializer list", nullptr));
+                JSON_THROW(type_error::create(301, "cannot create object from initializer list", nullptr));
             }
         }
 
@@ -2407,7 +2425,7 @@ public:
         // make sure the iterator fits the current value
         if (JSON_HEDLEY_UNLIKELY(first.m_object != last.m_object))
         {
-            JSON_THROW(invalid_iterator::create(detail::exception_id::iterators_incompatible, "iterators are not compatible", nullptr));
+            JSON_THROW(invalid_iterator::create(201, "iterators are not compatible", nullptr));
         }
 
         // copy type from the first iterator
@@ -2426,7 +2444,7 @@ public:
                 if (JSON_HEDLEY_UNLIKELY(!first.m_it.primitive_iterator.is_begin()
                                          || !last.m_it.primitive_iterator.is_end()))
                 {
-                    JSON_THROW(invalid_iterator::create(detail::exception_id::iterator_range_out_of_range, "iterators out of range", first.m_object));
+                    JSON_THROW(invalid_iterator::create(204, "iterators out of range", first.m_object));
                 }
                 break;
             }
@@ -2494,7 +2512,7 @@ public:
             case value_t::null:
             case value_t::discarded:
             default:
-                JSON_THROW(invalid_iterator::create(detail::exception_id::iterator_range_of_null, detail::concat("cannot construct with iterators from ", first.m_object->type_name()), first.m_object));
+                JSON_THROW(invalid_iterator::create(206, detail::concat("cannot construct with iterators from ", first.m_object->type_name()), first.m_object));
         }
 
         set_parents();
@@ -2882,7 +2900,7 @@ public:
             return *ptr;
         }
 
-        JSON_THROW(type_error::create(detail::exception_id::incompatible_reference_type, detail::concat("incompatible ReferenceType for get_ref, actual type is ", obj.type_name()), &obj));
+        JSON_THROW(type_error::create(303, detail::concat("incompatible ReferenceType for get_ref, actual type is ", obj.type_name()), &obj));
     }
 
   public:
@@ -3266,7 +3284,7 @@ public:
     {
         if (!is_binary())
         {
-            detail::throw_type_must_be("binary", *this);
+            JSON_THROW(type_error::create(302, detail::concat("type must be binary, but is ", type_name()), this));
         }
 
         return *get_ptr<binary_t*>();
@@ -3278,7 +3296,7 @@ public:
     {
         if (!is_binary())
         {
-            detail::throw_type_must_be("binary", *this);
+            JSON_THROW(type_error::create(302, detail::concat("type must be binary, but is ", type_name()), this));
         }
 
         return *get_ptr<const binary_t*>();
@@ -3320,7 +3338,7 @@ public:
         // at only works for objects
         if (JSON_HEDLEY_UNLIKELY(!j.is_object()))
         {
-            detail::throw_cannot_use_with(detail::exception_id::at_wrong_type, "at()", j);
+            JSON_THROW(type_error::create(304, detail::concat("cannot use at() with ", j.type_name()), &j));
         }
 
         auto it = object_lookup(j, std::forward<KeyType>(key));
@@ -3330,11 +3348,27 @@ public:
             // std::map or ordered_map) never moves from its argument, so key is still
             // valid here regardless of whether KeyType was deduced as an rvalue reference
             // NOLINTNEXTLINE(bugprone-use-after-move,hicpp-invalid-access-moved)
-            JSON_THROW(out_of_range::create(detail::exception_id::key_not_found, detail::concat("key '", string_t(key), "' not found"), &j));
+            JSON_THROW(out_of_range::create(403, detail::concat("key '", key_for_message(key), "' not found"), &j));
         }
         return it->second;
     }
 
+    /// @brief key as it is passed to detail::concat for an error message
+    /// @note string_t is used where it can be constructed from the key; other
+    ///       key types are passed through unchanged, as concat only needs
+    ///       data() and size() of them
+    template<typename KeyType, detail::enable_if_t<std::is_constructible<string_t, const KeyType&>::value, int> = 0>
+    static string_t key_for_message(const KeyType& key)
+    {
+        return string_t(key);
+    }
+
+    template < typename KeyType, detail::enable_if_t < !std::is_constructible<string_t, const KeyType&>::value, int > = 0 >
+    static const KeyType & key_for_message(const KeyType& key)
+    {
+        return key;
+    }
+
     /// @brief checked array element access used by the at() overloads taking an index
     /// @throw type_error.304 if @a j is not an array
     /// @throw out_of_range.401 if @a idx is out of range
@@ -3345,12 +3379,12 @@ public:
         // at only works for arrays
         if (JSON_HEDLEY_UNLIKELY(!j.is_array()))
         {
-            detail::throw_cannot_use_with(detail::exception_id::at_wrong_type, "at()", j);
+            JSON_THROW(type_error::create(304, detail::concat("cannot use at() with ", j.type_name()), &j));
         }
 
         if (JSON_HEDLEY_UNLIKELY(idx >= j.m_data.m_value.array->size()))
         {
-            JSON_THROW(out_of_range::create(detail::exception_id::array_index_out_of_range, detail::concat("array index ", std::to_string(idx), " is out of range"), &j));
+            JSON_THROW(out_of_range::create(401, detail::concat("array index ", std::to_string(idx), " is out of range"), &j));
         }
 
         return (*j.m_data.m_value.array)[idx];
@@ -3383,15 +3417,6 @@ public:
         m_data.m_type = value_t::object;
     }
 
-    /// @brief throws because operator[] is not supported for the type of this value
-    /// @param[in] argument  the kind of the operator's argument, "numeric" or "string"
-    /// @throw type_error.305 always
-    JSON_HEDLEY_NO_RETURN void throw_subscript_wrong_type(const char* argument) const
-    {
-        detail::throw_cannot_use_with(detail::exception_id::subscript_wrong_type,
-                                      detail::concat("operator[] with a ", argument, " argument").c_str(), *this);
-    }
-
   public:
     ////////////////////
     // element access //
@@ -3496,7 +3521,7 @@ public:
             return m_data.m_value.array->operator[](idx);
         }
 
-        throw_subscript_wrong_type("numeric");
+        JSON_THROW(type_error::create(305, detail::concat("cannot use operator[] with a numeric argument with ", type_name()), this));
     }
 
     /// @brief access specified array element
@@ -3510,7 +3535,7 @@ public:
             return m_data.m_value.array->operator[](idx);
         }
 
-        throw_subscript_wrong_type("numeric");
+        JSON_THROW(type_error::create(305, detail::concat("cannot use operator[] with a numeric argument with ", type_name()), this));
     }
 
     /// @brief access specified object element
@@ -3530,7 +3555,7 @@ public:
             return set_parent(result.first->second);
         }
 
-        throw_subscript_wrong_type("string");
+        JSON_THROW(type_error::create(305, detail::concat("cannot use operator[] with a string argument with ", type_name()), this));
     }
 
     /// @brief access specified object element
@@ -3545,7 +3570,7 @@ public:
             return it->second;
         }
 
-        throw_subscript_wrong_type("string");
+        JSON_THROW(type_error::create(305, detail::concat("cannot use operator[] with a string argument with ", type_name()), this));
     }
 
     // these two functions resolve a (const) char * ambiguity affecting Clang and MSVC
@@ -3581,7 +3606,7 @@ public:
             return set_parent(result.first->second);
         }
 
-        throw_subscript_wrong_type("string");
+        JSON_THROW(type_error::create(305, detail::concat("cannot use operator[] with a string argument with ", type_name()), this));
     }
 
     /// @brief access specified object element
@@ -3598,7 +3623,7 @@ public:
             return it->second;
         }
 
-        throw_subscript_wrong_type("string");
+        JSON_THROW(type_error::create(305, detail::concat("cannot use operator[] with a string argument with ", type_name()), this));
     }
 
   private:
@@ -3622,7 +3647,7 @@ public:
         // value only works for objects
         if (JSON_HEDLEY_UNLIKELY(!is_object()))
         {
-            detail::throw_cannot_use_with(detail::exception_id::value_wrong_type, "value()", *this);
+            JSON_THROW(type_error::create(306, detail::concat("cannot use value() with ", type_name()), this));
         }
 
         const auto it = find(std::forward<KeyType>(key));
@@ -3637,7 +3662,7 @@ public:
         // value only works for arrays and objects
         if (JSON_HEDLEY_UNLIKELY(!is_structured()))
         {
-            detail::throw_cannot_use_with(detail::exception_id::value_wrong_type, "value()", *this);
+            JSON_THROW(type_error::create(306, detail::concat("cannot use value() with ", type_name()), this));
         }
 
         return ptr.get_checked_or_null(this);
@@ -3804,7 +3829,7 @@ public:
         // make sure the iterator fits the current value
         if (JSON_HEDLEY_UNLIKELY(this != pos.m_object))
         {
-            JSON_THROW(invalid_iterator::create(detail::exception_id::iterator_from_other_value, "iterator does not fit current value", this));
+            JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value", this));
         }
 
         IteratorType result = end();
@@ -3820,7 +3845,7 @@ public:
             {
                 if (JSON_HEDLEY_UNLIKELY(!pos.m_it.primitive_iterator.is_begin()))
                 {
-                    JSON_THROW(invalid_iterator::create(detail::exception_id::iterator_out_of_range, "iterator out of range", this));
+                    JSON_THROW(invalid_iterator::create(205, "iterator out of range", this));
                 }
 
                 m_data.m_value.destroy(m_data.m_type);
@@ -3846,7 +3871,7 @@ public:
             case value_t::null:
             case value_t::discarded:
             default:
-                detail::throw_cannot_use_with(detail::exception_id::erase_wrong_type, "erase()", *this);
+                JSON_THROW(type_error::create(307, detail::concat("cannot use erase() with ", type_name()), this));
         }
 
         return result;
@@ -3862,7 +3887,7 @@ public:
         // make sure the iterator fits the current value
         if (JSON_HEDLEY_UNLIKELY(this != first.m_object || this != last.m_object))
         {
-            JSON_THROW(invalid_iterator::create(detail::exception_id::iterator_range_from_other_value, "iterators do not fit current value", this));
+            JSON_THROW(invalid_iterator::create(203, "iterators do not fit current value", this));
         }
 
         IteratorType result = end();
@@ -3879,7 +3904,7 @@ public:
                 if (JSON_HEDLEY_UNLIKELY(!first.m_it.primitive_iterator.is_begin()
                                          || !last.m_it.primitive_iterator.is_end()))
                 {
-                    JSON_THROW(invalid_iterator::create(detail::exception_id::iterator_range_out_of_range, "iterators out of range", this));
+                    JSON_THROW(invalid_iterator::create(204, "iterators out of range", this));
                 }
 
                 m_data.m_value.destroy(m_data.m_type);
@@ -3907,7 +3932,7 @@ public:
             case value_t::null:
             case value_t::discarded:
             default:
-                detail::throw_cannot_use_with(detail::exception_id::erase_wrong_type, "erase()", *this);
+                JSON_THROW(type_error::create(307, detail::concat("cannot use erase() with ", type_name()), this));
         }
 
         return result;
@@ -3921,7 +3946,7 @@ public:
         // this erase only works for objects
         if (JSON_HEDLEY_UNLIKELY(!is_object()))
         {
-            detail::throw_cannot_use_with(detail::exception_id::erase_wrong_type, "erase()", *this);
+            JSON_THROW(type_error::create(307, detail::concat("cannot use erase() with ", type_name()), this));
         }
 
         const auto erased = m_data.m_value.object->erase(std::forward<KeyType>(key));
@@ -3936,7 +3961,7 @@ public:
         // this erase only works for objects
         if (JSON_HEDLEY_UNLIKELY(!is_object()))
         {
-            detail::throw_cannot_use_with(detail::exception_id::erase_wrong_type, "erase()", *this);
+            JSON_THROW(type_error::create(307, detail::concat("cannot use erase() with ", type_name()), this));
         }
 
         const auto it = object_lookup(*this, std::forward<KeyType>(key));
@@ -3978,14 +4003,14 @@ public:
         {
             if (JSON_HEDLEY_UNLIKELY(idx >= size()))
             {
-                JSON_THROW(out_of_range::create(detail::exception_id::array_index_out_of_range, detail::concat("array index ", std::to_string(idx), " is out of range"), this));
+                JSON_THROW(out_of_range::create(401, detail::concat("array index ", std::to_string(idx), " is out of range"), this));
             }
 
             m_data.m_value.array->erase(m_data.m_value.array->begin() + static_cast<difference_type>(idx));
         }
         else
         {
-            detail::throw_cannot_use_with(detail::exception_id::erase_wrong_type, "erase()", *this);
+            JSON_THROW(type_error::create(307, detail::concat("cannot use erase() with ", type_name()), this));
         }
     }
 
@@ -4474,7 +4499,7 @@ public:
         // push_back only works for null objects or arrays
         if (JSON_HEDLEY_UNLIKELY(!(is_null() || is_array())))
         {
-            detail::throw_cannot_use_with(detail::exception_id::push_back_wrong_type, "push_back()", *this);
+            JSON_THROW(type_error::create(308, detail::concat("cannot use push_back() with ", type_name()), this));
         }
 
         // transform a null object into an array
@@ -4505,7 +4530,7 @@ public:
         // push_back only works for null objects or arrays
         if (JSON_HEDLEY_UNLIKELY(!(is_null() || is_array())))
         {
-            detail::throw_cannot_use_with(detail::exception_id::push_back_wrong_type, "push_back()", *this);
+            JSON_THROW(type_error::create(308, detail::concat("cannot use push_back() with ", type_name()), this));
         }
 
         // transform a null object into an array
@@ -4535,7 +4560,7 @@ public:
         // push_back only works for null objects or objects
         if (JSON_HEDLEY_UNLIKELY(!(is_null() || is_object())))
         {
-            detail::throw_cannot_use_with(detail::exception_id::push_back_wrong_type, "push_back()", *this);
+            JSON_THROW(type_error::create(308, detail::concat("cannot use push_back() with ", type_name()), this));
         }
 
         // transform a null object into an object
@@ -4589,7 +4614,7 @@ public:
         // emplace_back only works for null objects or arrays
         if (JSON_HEDLEY_UNLIKELY(!(is_null() || is_array())))
         {
-            detail::throw_cannot_use_with(detail::exception_id::emplace_wrong_type, "emplace_back()", *this);
+            JSON_THROW(type_error::create(311, detail::concat("cannot use emplace_back() with ", type_name()), this));
         }
 
         // transform a null object into an array
@@ -4612,7 +4637,7 @@ public:
         // emplace only works for null objects or arrays
         if (JSON_HEDLEY_UNLIKELY(!(is_null() || is_object())))
         {
-            detail::throw_cannot_use_with(detail::exception_id::emplace_wrong_type, "emplace()", *this);
+            JSON_THROW(type_error::create(311, detail::concat("cannot use emplace() with ", type_name()), this));
         }
 
         // transform a null object into an object
@@ -4664,14 +4689,14 @@ public:
             // check if iterator pos fits to this JSON value
             if (JSON_HEDLEY_UNLIKELY(pos.m_object != this))
             {
-                JSON_THROW(invalid_iterator::create(detail::exception_id::iterator_from_other_value, "iterator does not fit current value", this));
+                JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value", this));
             }
 
             // insert to array and return iterator
             return insert_iterator(pos, val);
         }
 
-        detail::throw_cannot_use_with(detail::exception_id::insert_wrong_type, "insert()", *this);
+        JSON_THROW(type_error::create(309, detail::concat("cannot use insert() with ", type_name()), this));
     }
 
     /// @brief inserts element into array
@@ -4684,7 +4709,7 @@ public:
             // check if iterator pos fits to this JSON value
             if (JSON_HEDLEY_UNLIKELY(pos.m_object != this))
             {
-                JSON_THROW(invalid_iterator::create(detail::exception_id::iterator_from_other_value, "iterator does not fit current value", this));
+                JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value", this));
             }
 
             // moving into a local first keeps this safe even if val aliases
@@ -4693,7 +4718,7 @@ public:
             return insert_iterator(pos, std::move(tmp));
         }
 
-        detail::throw_cannot_use_with(detail::exception_id::insert_wrong_type, "insert()", *this);
+        JSON_THROW(type_error::create(309, detail::concat("cannot use insert() with ", type_name()), this));
     }
 
     /// @brief inserts copies of element into array
@@ -4706,14 +4731,14 @@ public:
             // check if iterator pos fits to this JSON value
             if (JSON_HEDLEY_UNLIKELY(pos.m_object != this))
             {
-                JSON_THROW(invalid_iterator::create(detail::exception_id::iterator_from_other_value, "iterator does not fit current value", this));
+                JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value", this));
             }
 
             // insert to array and return iterator
             return insert_iterator(pos, cnt, val);
         }
 
-        detail::throw_cannot_use_with(detail::exception_id::insert_wrong_type, "insert()", *this);
+        JSON_THROW(type_error::create(309, detail::concat("cannot use insert() with ", type_name()), this));
     }
 
     /// @brief inserts range of elements into array
@@ -4723,30 +4748,30 @@ public:
         // insert only works for arrays
         if (JSON_HEDLEY_UNLIKELY(!is_array()))
         {
-            detail::throw_cannot_use_with(detail::exception_id::insert_wrong_type, "insert()", *this);
+            JSON_THROW(type_error::create(309, detail::concat("cannot use insert() with ", type_name()), this));
         }
 
         // check if iterator pos fits to this JSON value
         if (JSON_HEDLEY_UNLIKELY(pos.m_object != this))
         {
-            JSON_THROW(invalid_iterator::create(detail::exception_id::iterator_from_other_value, "iterator does not fit current value", this));
+            JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value", this));
         }
 
         // check if range iterators belong to the same JSON object
         if (JSON_HEDLEY_UNLIKELY(first.m_object != last.m_object))
         {
-            JSON_THROW(invalid_iterator::create(detail::exception_id::insert_range_incompatible, "iterators do not fit", this));
+            JSON_THROW(invalid_iterator::create(210, "iterators do not fit", this));
         }
 
         if (JSON_HEDLEY_UNLIKELY(first.m_object == this))
         {
-            JSON_THROW(invalid_iterator::create(detail::exception_id::insert_range_into_itself, "passed iterators may not belong to container", this));
+            JSON_THROW(invalid_iterator::create(211, "passed iterators may not belong to container", this));
         }
 
         // passed iterators must belong to arrays
         if (JSON_HEDLEY_UNLIKELY(!first.m_object->is_array()))
         {
-            JSON_THROW(invalid_iterator::create(detail::exception_id::iterator_from_other_value, "iterators first and last must point to arrays", this));
+            JSON_THROW(invalid_iterator::create(202, "iterators first and last must point to arrays", this));
         }
 
         // insert to array and return iterator
@@ -4760,13 +4785,13 @@ public:
         // insert only works for arrays
         if (JSON_HEDLEY_UNLIKELY(!is_array()))
         {
-            detail::throw_cannot_use_with(detail::exception_id::insert_wrong_type, "insert()", *this);
+            JSON_THROW(type_error::create(309, detail::concat("cannot use insert() with ", type_name()), this));
         }
 
         // check if iterator pos fits to this JSON value
         if (JSON_HEDLEY_UNLIKELY(pos.m_object != this))
         {
-            JSON_THROW(invalid_iterator::create(detail::exception_id::iterator_from_other_value, "iterator does not fit current value", this));
+            JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value", this));
         }
 
         // copy the values first: ilist may refer to elements of this array
@@ -4788,19 +4813,19 @@ public:
         // insert only works for objects
         if (JSON_HEDLEY_UNLIKELY(!is_object()))
         {
-            detail::throw_cannot_use_with(detail::exception_id::insert_wrong_type, "insert()", *this);
+            JSON_THROW(type_error::create(309, detail::concat("cannot use insert() with ", type_name()), this));
         }
 
         // check if range iterators belong to the same JSON object
         if (JSON_HEDLEY_UNLIKELY(first.m_object != last.m_object))
         {
-            JSON_THROW(invalid_iterator::create(detail::exception_id::insert_range_incompatible, "iterators do not fit", this));
+            JSON_THROW(invalid_iterator::create(210, "iterators do not fit", this));
         }
 
         // passed iterators must belong to objects
         if (JSON_HEDLEY_UNLIKELY(!first.m_object->is_object()))
         {
-            JSON_THROW(invalid_iterator::create(detail::exception_id::iterator_from_other_value, "iterators first and last must point to objects", this));
+            JSON_THROW(invalid_iterator::create(202, "iterators first and last must point to objects", this));
         }
 
         m_data.m_value.object->insert(first.m_it.object_iterator, last.m_it.object_iterator);
@@ -4817,7 +4842,7 @@ public:
         // j, not the copy made below)
         if (JSON_HEDLEY_UNLIKELY(!j.is_object()))
         {
-            detail::throw_cannot_use_with(detail::exception_id::update_wrong_type, "update()", j);
+            JSON_THROW(type_error::create(312, detail::concat("cannot use update() with ", j.type_name()), &j));
         }
 
         // copy first: j may be *this or one of its descendants, and is
@@ -4835,13 +4860,13 @@ public:
         // check if range iterators belong to the same JSON object
         if (JSON_HEDLEY_UNLIKELY(first.m_object != last.m_object))
         {
-            JSON_THROW(invalid_iterator::create(detail::exception_id::insert_range_incompatible, "iterators do not fit", this));
+            JSON_THROW(invalid_iterator::create(210, "iterators do not fit", this));
         }
 
         // passed iterators must belong to objects
         if (JSON_HEDLEY_UNLIKELY(!first.m_object->is_object()))
         {
-            detail::throw_cannot_use_with(detail::exception_id::update_wrong_type, "update()", *first.m_object);
+            JSON_THROW(type_error::create(312, detail::concat("cannot use update() with ", first.m_object->type_name()), first.m_object));
         }
 
         // copy first: the range may belong to *this or one of its
@@ -4877,7 +4902,7 @@ public:
 
         if (JSON_HEDLEY_UNLIKELY(!is_object()))
         {
-            detail::throw_cannot_use_with(detail::exception_id::update_wrong_type, "update()", *this);
+            JSON_THROW(type_error::create(312, detail::concat("cannot use update() with ", type_name()), this));
         }
     }
 
@@ -5040,7 +5065,7 @@ public:
         }
         else
         {
-            detail::throw_cannot_use_with(detail::exception_id::swap_wrong_type, "swap(array_t&)", *this);
+            JSON_THROW(type_error::create(310, detail::concat("cannot use swap(array_t&) with ", type_name()), this));
         }
     }
 
@@ -5057,7 +5082,7 @@ public:
         }
         else
         {
-            detail::throw_cannot_use_with(detail::exception_id::swap_wrong_type, "swap(object_t&)", *this);
+            JSON_THROW(type_error::create(310, detail::concat("cannot use swap(object_t&) with ", type_name()), this));
         }
     }
 
@@ -5073,7 +5098,7 @@ public:
         }
         else
         {
-            detail::throw_cannot_use_with(detail::exception_id::swap_wrong_type, "swap(string_t&)", *this);
+            JSON_THROW(type_error::create(310, detail::concat("cannot use swap(string_t&) with ", type_name()), this));
         }
     }
 
@@ -5089,7 +5114,7 @@ public:
         }
         else
         {
-            detail::throw_cannot_use_with(detail::exception_id::swap_wrong_type, "swap(binary_t&)", *this);
+            JSON_THROW(type_error::create(310, detail::concat("cannot use swap(binary_t&) with ", type_name()), this));
         }
     }
 
@@ -5105,7 +5130,7 @@ public:
         }
         else
         {
-            detail::throw_cannot_use_with(detail::exception_id::swap_wrong_type, "swap(binary_t::container_type&)", *this);
+            JSON_THROW(type_error::create(310, detail::concat("cannot use swap(binary_t::container_type&) with ", type_name()), this));
         }
     }
 
@@ -6567,7 +6592,7 @@ public:
                         if (JSON_HEDLEY_UNLIKELY(idx > parent.size()))
                         {
                             // avoid undefined behavior
-                            JSON_THROW(out_of_range::create(detail::exception_id::array_index_out_of_range, detail::concat("array index ", std::to_string(idx), " is out of range"), &parent));
+                            JSON_THROW(out_of_range::create(401, detail::concat("array index ", std::to_string(idx), " is out of range"), &parent));
                         }
 
                         // default case: insert add offset
@@ -6586,7 +6611,7 @@ public:
                 case value_t::binary:
                 case value_t::discarded:
                 default:
-                    JSON_THROW(out_of_range::create(detail::exception_id::patch_add_parent_not_container, detail::concat("cannot add value: the JSON Patch 'add' target's parent is of type ", parent.type_name(), ", but must be an object or array"), &parent));
+                    JSON_THROW(out_of_range::create(411, detail::concat("cannot add value: the JSON Patch 'add' target's parent is of type ", parent.type_name(), ", but must be an object or array"), &parent));
             }
         };
 
@@ -6609,7 +6634,7 @@ public:
                 }
                 else
                 {
-                    JSON_THROW(out_of_range::create(detail::exception_id::key_not_found, detail::concat("key '", last_path, "' not found"), this));
+                    JSON_THROW(out_of_range::create(403, detail::concat("key '", last_path, "' not found"), this));
                 }
             }
             else if (parent.is_array())
@@ -6621,7 +6646,7 @@ public:
             {
                 // the parent of a "remove" target must be an object or array
                 // (see #5396)
-                JSON_THROW(out_of_range::create(detail::exception_id::patch_remove_parent_not_container, detail::concat("cannot remove value: the JSON Patch 'remove' target's parent is of type ", parent.type_name(), ", but must be an object or array"), &parent));
+                JSON_THROW(out_of_range::create(413, detail::concat("cannot remove value: the JSON Patch 'remove' target's parent is of type ", parent.type_name(), ", but must be an object or array"), &parent));
             }
         };
 
@@ -6652,7 +6677,7 @@ public:
         // type check: top level value must be an array
         if (JSON_HEDLEY_UNLIKELY(!json_patch.is_array()))
         {
-            JSON_THROW(parse_error::create(detail::exception_id::patch_not_an_array, 0, "JSON patch must be an array of objects", &json_patch));
+            JSON_THROW(parse_error::create(104, 0, "JSON patch must be an array of objects", &json_patch));
         }
 
         // iterate and apply the operations
@@ -6673,14 +6698,14 @@ public:
                 if (JSON_HEDLEY_UNLIKELY(it == val.m_data.m_value.object->end()))
                 {
                     // NOLINTNEXTLINE(performance-inefficient-string-concatenation)
-                    JSON_THROW(parse_error::create(detail::exception_id::patch_invalid_operation, 0, detail::concat(error_msg, " must have member '", member, "'"), &val));
+                    JSON_THROW(parse_error::create(105, 0, detail::concat(error_msg, " must have member '", member, "'"), &val));
                 }
 
                 // check if the result is of type string
                 if (JSON_HEDLEY_UNLIKELY(string_type && !it->second.is_string()))
                 {
                     // NOLINTNEXTLINE(performance-inefficient-string-concatenation)
-                    JSON_THROW(parse_error::create(detail::exception_id::patch_invalid_operation, 0, detail::concat(error_msg, " must have string member '", member, "'"), &val));
+                    JSON_THROW(parse_error::create(105, 0, detail::concat(error_msg, " must have string member '", member, "'"), &val));
                 }
 
                 // no error: return value
@@ -6690,7 +6715,7 @@ public:
             // type check: every element of the array must be an object
             if (JSON_HEDLEY_UNLIKELY(!val.is_object()))
             {
-                JSON_THROW(parse_error::create(detail::exception_id::patch_not_an_array, 0, "JSON patch must be an array of objects", &val));
+                JSON_THROW(parse_error::create(104, 0, "JSON patch must be an array of objects", &val));
             }
 
             // collect mandatory members
@@ -6726,7 +6751,7 @@ public:
 
                     if (JSON_HEDLEY_UNLIKELY(is_proper_prefix(from_ptr, ptr)))
                     {
-                        JSON_THROW(out_of_range::create(detail::exception_id::patch_move_into_child, detail::concat("cannot move value: 'from' path '", from_path, "' is a proper prefix of 'path' '", path, "'"), &result));
+                        JSON_THROW(out_of_range::create(414, detail::concat("cannot move value: 'from' path '", from_path, "' is a proper prefix of 'path' '", path, "'"), &result));
                     }
 
                     // the "from" location must exist - use at()
@@ -6773,7 +6798,7 @@ public:
                     // throw an exception if the test fails
                     if (JSON_HEDLEY_UNLIKELY(!success))
                     {
-                        JSON_THROW(other_error::create(detail::exception_id::patch_test_failed, detail::concat("unsuccessful: ", val.dump()), &val));
+                        JSON_THROW(other_error::create(501, detail::concat("unsuccessful: ", val.dump()), &val));
                     }
 
                     break;
@@ -6784,7 +6809,7 @@ public:
                 {
                     // op must be "add", "remove", "replace", "move", "copy", or
                     // "test"
-                    JSON_THROW(parse_error::create(detail::exception_id::patch_invalid_operation, 0, detail::concat("operation value '", op, "' is invalid"), &val));
+                    JSON_THROW(parse_error::create(105, 0, detail::concat("operation value '", op, "' is invalid"), &val));
                 }
             }
         }

include/nlohmann/ordered_map.hpp

@@ -90,19 +90,6 @@ private:
         return self.end();
     }
 
-    /// @brief shared implementation of the const and non-const at() overloads
-    /// @throw std::out_of_range if @a key is not found
-    template<typename Self, typename KeyType>
-    static auto at_impl(Self& self, const KeyType& key) -> decltype((self.begin()->second))
-    {
-        const auto it = find_impl(self, key);
-        if (it == self.end())
-        {
-            JSON_THROW(std::out_of_range("key not found"));
-        }
-        return it->second;
-    }
-
     /// @brief remove the entry @a it points to, preserving order
     /// @note keys are not movable, so the tail is destroyed and re-constructed in place
     void erase_at(iterator it)
@@ -169,26 +156,46 @@ public:
 
     T& at(const key_type& key)
     {
-        return at_impl(*this, key);
+        const auto it = find_impl(*this, key);
+        if (it == this->end())
+        {
+            JSON_THROW(std::out_of_range("key not found"));
+        }
+        return it->second;
     }
 
     template<class KeyType, detail::enable_if_t<
                  detail::is_usable_as_key_type<key_compare, key_type, KeyType>::value, int> = 0>
     T & at(KeyType && key) // NOLINT(cppcoreguidelines-missing-std-forward)
     {
-        return at_impl(*this, key);
+        const auto it = find_impl(*this, key);
+        if (it == this->end())
+        {
+            JSON_THROW(std::out_of_range("key not found"));
+        }
+        return it->second;
     }
 
     const T& at(const key_type& key) const
     {
-        return at_impl(*this, key);
+        const auto it = find_impl(*this, key);
+        if (it == this->end())
+        {
+            JSON_THROW(std::out_of_range("key not found"));
+        }
+        return it->second;
     }
 
     template<class KeyType, detail::enable_if_t<
                  detail::is_usable_as_key_type<key_compare, key_type, KeyType>::value, int> = 0>
     const T & at(KeyType && key) const // NOLINT(cppcoreguidelines-missing-std-forward)
     {
-        return at_impl(*this, key);
+        const auto it = find_impl(*this, key);
+        if (it == this->end())
+        {
+            JSON_THROW(std::out_of_range("key not found"));
+        }
+        return it->second;
     }
 
     size_type erase(const key_type& key)

tests/CMakeLists.txt

@@ -138,7 +138,8 @@ json_test_set_test_options(test-disabled_exceptions
 # only the #972 regression test needs thirdparty/fifo_map on its include path
 json_test_set_test_options(test-regression1 LINK_LIBRARIES fifo_map_include)
 
-# GCC's false -Warray-bounds error with JSON_DIAGNOSTICS only shows up when optimizing (#5742).
+# Regression test for GCC's false -Warray-bounds error with JSON_DIAGNOSTICS (#5742, fixed in #5585). It only
+# showed up when optimizing, so build this test with -O3 and the warning as an error.
 # -O3 makes the optimizer-driven warnings of the ci_test_gcc flag set (-Winline,
 # -Wsuggest-attribute=...) fire on the library's inline functions; they are not
 # what this test checks, so turn them off for it.

tests/src/custom_object_key_type.hpp

@@ -0,0 +1,75 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <map>
+#include <memory>
+#include <string>
+#include <utility>
+#include <nlohmann/json.hpp>
+
+namespace custom_object_key_test
+{
+class key
+{
+  public:
+    key() = default;
+
+    key(const char* value)
+        : m_value(value)
+    {}
+
+    key(std::string value)
+        : m_value(std::move(value))
+    {}
+
+    operator std::string() const
+    {
+        return m_value;
+    }
+
+    // Required by JSON_DIAGNOSTICS, which reads object keys through data()
+    // when building the path of an exception.
+    const char* data() const noexcept
+    {
+        return m_value.data();
+    }
+
+    friend bool operator<(const key& lhs, const key& rhs)
+    {
+        return lhs.m_value < rhs.m_value;
+    }
+
+  private:
+    std::string m_value;
+};
+
+template<typename Key, typename Value, typename Compare, typename Allocator>
+class object
+    : public std::map <
+      key,
+      Value,
+      std::less<key>, // NOLINT(modernize-use-transparent-functors)
+      typename std::allocator_traits<Allocator>::template rebind_alloc <
+          std::pair<const key, Value >>>
+{
+  private:
+    using allocator_type =
+    typename std::allocator_traits<Allocator>::template rebind_alloc <
+        std::pair<const key, Value >>;
+
+    using base_type =
+        std::map<key, Value, std::less<key>, allocator_type>; // NOLINT(modernize-use-transparent-functors)
+
+  public:
+    using base_type::base_type;
+};
+
+using json = nlohmann::json::with_object_t<object>;
+} // namespace custom_object_key_test

tests/src/fuzzer-parse_bjdata.cpp

@@ -51,7 +51,22 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
-#include "fuzzer_common.hpp"
+#include <cassert>
+#include <nlohmann/json.hpp>
+
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
+using json = nlohmann::json;
+
+// compares dumps rather than values, because NaN != NaN; keep writes strings
+// byte for byte, so ill-formed UTF-8 that a binary reader accepts cannot throw
+static bool same_value(const json& lhs, const json& rhs)
+{
+    return lhs.dump(-1, ' ', false, json::error_handler_t::keep) == rhs.dump(-1, ' ', false, json::error_handler_t::keep);
+}
 
 // value-stable comparison for the round-trip checks below; see the note
 // above on why this compares dump()s rather than the json values directly
@@ -65,9 +80,23 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
     std::vector<uint8_t> const vec1(data, data + size);
 
-    // step 0: parse input without exceptions
+    // step 0: parse input without exceptions; a parse error must then be
+    // reported as a discarded value, never thrown
+    json j_noexcept;
     bool noexcept_threw = false;
-    json const j_noexcept = parse_without_exceptions([&] { return json::from_bjdata(vec1, true, false); }, noexcept_threw);
+    try
+    {
+        j_noexcept = json::from_bjdata(vec1, true, false);
+    }
+    catch (const json::parse_error&)
+    {
+        assert(false);
+    }
+    catch (const json::exception&)
+    {
+        // type and out-of-range errors are not parse errors and still throw
+        noexcept_threw = true;
+    }
     // whether step 1 succeeded; if not, the catch blocks below check that
     // step 0 failed, too
     bool parsed = false;

tests/src/fuzzer-parse_bon8.cpp

@@ -25,8 +25,23 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
+#include <cassert>
 #include <sstream>
-#include "fuzzer_common.hpp"
+#include <nlohmann/json.hpp>
+
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
+using json = nlohmann::json;
+
+// compares dumps rather than values, because NaN != NaN; keep writes strings
+// byte for byte, so ill-formed UTF-8 that a binary reader accepts cannot throw
+static bool same_value(const json& lhs, const json& rhs)
+{
+    return lhs.dump(-1, ' ', false, json::error_handler_t::keep) == rhs.dump(-1, ' ', false, json::error_handler_t::keep);
+}
 
 namespace
 {
@@ -57,9 +72,23 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 
     std::vector<uint8_t> const vec1(data, data + size);
 
-    // step 0: parse input without exceptions
+    // step 0: parse input without exceptions; a parse error must then be
+    // reported as a discarded value, never thrown
+    json j_noexcept;
     bool noexcept_threw = false;
-    json const j_noexcept = parse_without_exceptions([&] { return json::from_bon8(vec1, true, false); }, noexcept_threw);
+    try
+    {
+        j_noexcept = json::from_bon8(vec1, true, false);
+    }
+    catch (const json::parse_error&)
+    {
+        assert(false);
+    }
+    catch (const json::exception&)
+    {
+        // type and out-of-range errors are not parse errors and still throw
+        noexcept_threw = true;
+    }
     // whether step 1 succeeded; if not, the catch blocks below check that
     // step 0 failed, too
     bool parsed = false;

tests/src/fuzzer-parse_bson.cpp

@@ -21,16 +21,45 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
-#include "fuzzer_common.hpp"
+#include <cassert>
+#include <nlohmann/json.hpp>
+
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
+using json = nlohmann::json;
+
+// compares dumps rather than values, because NaN != NaN; keep writes strings
+// byte for byte, so ill-formed UTF-8 that a binary reader accepts cannot throw
+static bool same_value(const json& lhs, const json& rhs)
+{
+    return lhs.dump(-1, ' ', false, json::error_handler_t::keep) == rhs.dump(-1, ' ', false, json::error_handler_t::keep);
+}
 
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
     std::vector<uint8_t> const vec1(data, data + size);
 
-    // step 0: parse input without exceptions
+    // step 0: parse input without exceptions; a parse error must then be
+    // reported as a discarded value, never thrown
+    json j_noexcept;
     bool noexcept_threw = false;
-    json const j_noexcept = parse_without_exceptions([&] { return json::from_bson(vec1, true, false); }, noexcept_threw);
+    try
+    {
+        j_noexcept = json::from_bson(vec1, true, false);
+    }
+    catch (const json::parse_error&)
+    {
+        assert(false);
+    }
+    catch (const json::exception&)
+    {
+        // type and out-of-range errors are not parse errors and still throw
+        noexcept_threw = true;
+    }
     // whether step 1 succeeded; if not, the catch blocks below check that
     // step 0 failed, too
     bool parsed = false;

tests/src/fuzzer-parse_cbor.cpp

@@ -21,16 +21,45 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
-#include "fuzzer_common.hpp"
+#include <cassert>
+#include <nlohmann/json.hpp>
+
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
+using json = nlohmann::json;
+
+// compares dumps rather than values, because NaN != NaN; keep writes strings
+// byte for byte, so ill-formed UTF-8 that a binary reader accepts cannot throw
+static bool same_value(const json& lhs, const json& rhs)
+{
+    return lhs.dump(-1, ' ', false, json::error_handler_t::keep) == rhs.dump(-1, ' ', false, json::error_handler_t::keep);
+}
 
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
     std::vector<uint8_t> const vec1(data, data + size);
 
-    // step 0: parse input without exceptions
+    // step 0: parse input without exceptions; a parse error must then be
+    // reported as a discarded value, never thrown
+    json j_noexcept;
     bool noexcept_threw = false;
-    json const j_noexcept = parse_without_exceptions([&] { return json::from_cbor(vec1, true, false); }, noexcept_threw);
+    try
+    {
+        j_noexcept = json::from_cbor(vec1, true, false);
+    }
+    catch (const json::parse_error&)
+    {
+        assert(false);
+    }
+    catch (const json::exception&)
+    {
+        // type and out-of-range errors are not parse errors and still throw
+        noexcept_threw = true;
+    }
     // whether step 1 succeeded; if not, the catch blocks below check that
     // step 0 failed, too
     bool parsed = false;

tests/src/fuzzer-parse_json.cpp

@@ -22,14 +22,43 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
-#include "fuzzer_common.hpp"
+#include <cassert>
+#include <nlohmann/json.hpp>
+
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
+using json = nlohmann::json;
+
+// compares dumps rather than values, because NaN != NaN; keep writes strings
+// byte for byte, so ill-formed UTF-8 that a binary reader accepts cannot throw
+static bool same_value(const json& lhs, const json& rhs)
+{
+    return lhs.dump(-1, ' ', false, json::error_handler_t::keep) == rhs.dump(-1, ' ', false, json::error_handler_t::keep);
+}
 
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
-    // step 0: parse input without exceptions
+    // step 0: parse input without exceptions; a parse error must then be
+    // reported as a discarded value, never thrown
+    json j_noexcept;
     bool noexcept_threw = false;
-    json const j_noexcept = parse_without_exceptions([&] { return json::parse(data, data + size, nullptr, false); }, noexcept_threw);
+    try
+    {
+        j_noexcept = json::parse(data, data + size, nullptr, false);
+    }
+    catch (const json::parse_error&)
+    {
+        assert(false);
+    }
+    catch (const json::exception&)
+    {
+        // type and out-of-range errors are not parse errors and still throw
+        noexcept_threw = true;
+    }
     // whether step 1 succeeded; if not, the catch blocks below check that
     // step 0 failed, too
     bool parsed = false;

tests/src/fuzzer-parse_msgpack.cpp

@@ -21,16 +21,45 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
-#include "fuzzer_common.hpp"
+#include <cassert>
+#include <nlohmann/json.hpp>
+
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
+using json = nlohmann::json;
+
+// compares dumps rather than values, because NaN != NaN; keep writes strings
+// byte for byte, so ill-formed UTF-8 that a binary reader accepts cannot throw
+static bool same_value(const json& lhs, const json& rhs)
+{
+    return lhs.dump(-1, ' ', false, json::error_handler_t::keep) == rhs.dump(-1, ' ', false, json::error_handler_t::keep);
+}
 
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
     std::vector<uint8_t> const vec1(data, data + size);
 
-    // step 0: parse input without exceptions
+    // step 0: parse input without exceptions; a parse error must then be
+    // reported as a discarded value, never thrown
+    json j_noexcept;
     bool noexcept_threw = false;
-    json const j_noexcept = parse_without_exceptions([&] { return json::from_msgpack(vec1, true, false); }, noexcept_threw);
+    try
+    {
+        j_noexcept = json::from_msgpack(vec1, true, false);
+    }
+    catch (const json::parse_error&)
+    {
+        assert(false);
+    }
+    catch (const json::exception&)
+    {
+        // type and out-of-range errors are not parse errors and still throw
+        noexcept_threw = true;
+    }
     // whether step 1 succeeded; if not, the catch blocks below check that
     // step 0 failed, too
     bool parsed = false;

tests/src/fuzzer-parse_ubjson.cpp

@@ -30,16 +30,45 @@ The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */
 
-#include "fuzzer_common.hpp"
+#include <cassert>
+#include <nlohmann/json.hpp>
+
+// the round-trip checks below are assertions; NDEBUG would compile them away
+#ifdef NDEBUG
+    #error "the fuzzer drivers must be built without NDEBUG"
+#endif
+
+using json = nlohmann::json;
+
+// compares dumps rather than values, because NaN != NaN; keep writes strings
+// byte for byte, so ill-formed UTF-8 that a binary reader accepts cannot throw
+static bool same_value(const json& lhs, const json& rhs)
+{
+    return lhs.dump(-1, ' ', false, json::error_handler_t::keep) == rhs.dump(-1, ' ', false, json::error_handler_t::keep);
+}
 
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
     std::vector<uint8_t> const vec1(data, data + size);
 
-    // step 0: parse input without exceptions
+    // step 0: parse input without exceptions; a parse error must then be
+    // reported as a discarded value, never thrown
+    json j_noexcept;
     bool noexcept_threw = false;
-    json const j_noexcept = parse_without_exceptions([&] { return json::from_ubjson(vec1, true, false); }, noexcept_threw);
+    try
+    {
+        j_noexcept = json::from_ubjson(vec1, true, false);
+    }
+    catch (const json::parse_error&)
+    {
+        assert(false);
+    }
+    catch (const json::exception&)
+    {
+        // type and out-of-range errors are not parse errors and still throw
+        noexcept_threw = true;
+    }
     // whether step 1 succeeded; if not, the catch blocks below check that
     // step 0 failed, too
     bool parsed = false;

tests/src/fuzzer_common.hpp

@@ -1,51 +0,0 @@
-//     __ _____ _____ _____
-//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
-// |  |  |__   |  |  | | | |  version 3.12.0
-// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
-//
-// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
-// SPDX-License-Identifier: MIT
-
-// code shared by the fuzzer drivers tests/src/fuzzer-parse_*.cpp
-
-#pragma once
-
-#include <cassert> // assert
-#include <nlohmann/json.hpp>
-
-using nlohmann::json; // NOLINT(google-global-names-in-headers): shared by all fuzzer drivers
-
-// the round-trip checks of the drivers are assertions; NDEBUG would compile them away
-#ifdef NDEBUG
-    #error "the fuzzer drivers must be built without NDEBUG"
-#endif
-
-// compares dumps rather than values, because NaN != NaN; keep writes strings
-// byte for byte, so ill-formed UTF-8 that a binary reader accepts cannot throw
-inline bool same_value(const json& lhs, const json& rhs)
-{
-    return lhs.dump(-1, ' ', false, json::error_handler_t::keep) == rhs.dump(-1, ' ', false, json::error_handler_t::keep);
-}
-
-// step 0 of each driver: parse the input without exceptions; a parse error
-// must then be reported as a discarded value, never thrown. Type and
-// out-of-range errors are not parse errors and still throw; then @a threw is
-// set and null is returned.
-template<typename Parse>
-json parse_without_exceptions(Parse parse, bool& threw)
-{
-    threw = false;
-    try
-    {
-        return parse();
-    }
-    catch (const json::parse_error&)
-    {
-        assert(false);
-    }
-    catch (const json::exception&)
-    {
-        threw = true;
-    }
-    return {};
-}

tests/src/sax_event_loggers.hpp

@@ -1,185 +0,0 @@
-//     __ _____ _____ _____
-//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
-// |  |  |__   |  |  | | | |  version 3.12.0
-// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
-//
-// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
-// SPDX-License-Identifier: MIT
-
-#pragma once
-
-#include <cstddef> // size_t
-#include <cstdint> // uint8_t (via json::binary_t)
-#include <limits> // numeric_limits
-#include <string> // string, to_string
-#include <vector> // vector
-
-#include <nlohmann/json.hpp>
-
-// the loggers are defined in this header only, so their vtables are emitted in
-// every test that includes it
-#if defined(__clang__)
-    #pragma clang diagnostic push
-    #pragma clang diagnostic ignored "-Wweak-vtables"
-#endif
-
-namespace utils
-{
-/// a SAX event consumer that records every event it receives as a
-/// human-readable string, used by the deserialization tests to check the
-/// exact sequence of SAX events a parse run produces
-struct SaxEventLogger : public nlohmann::json_sax<nlohmann::json>
-{
-    using json = nlohmann::json;
-
-    bool null() override
-    {
-        events.emplace_back("null()");
-        return true;
-    }
-
-    bool boolean(bool val) override
-    {
-        events.emplace_back(val ? "boolean(true)" : "boolean(false)");
-        return true;
-    }
-
-    bool number_integer(json::number_integer_t val) override
-    {
-        events.push_back("number_integer(" + std::to_string(val) + ")");
-        return true;
-    }
-
-    bool number_unsigned(json::number_unsigned_t val) override
-    {
-        events.push_back("number_unsigned(" + std::to_string(val) + ")");
-        return true;
-    }
-
-    bool number_float(json::number_float_t /*val*/, const std::string& s) override
-    {
-        events.push_back("number_float(" + s + ")");
-        return true;
-    }
-
-    bool string(std::string& val) override
-    {
-        events.push_back("string(" + val + ")");
-        return true;
-    }
-
-    bool binary(json::binary_t& val) override
-    {
-        std::string binary_contents = "binary(";
-        std::string comma_space;
-        for (const auto b : val)
-        {
-            binary_contents.append(comma_space);
-            binary_contents.append(std::to_string(static_cast<int>(b)));
-            comma_space = ", ";
-        }
-        binary_contents.append(")");
-        events.push_back(binary_contents);
-        return true;
-    }
-
-    bool start_object(std::size_t elements) override
-    {
-        if (elements == (std::numeric_limits<std::size_t>::max)())
-        {
-            events.emplace_back("start_object()");
-        }
-        else
-        {
-            events.push_back("start_object(" + std::to_string(elements) + ")");
-        }
-        return true;
-    }
-
-    bool key(std::string& val) override
-    {
-        events.push_back("key(" + val + ")");
-        return true;
-    }
-
-    bool end_object() override
-    {
-        events.emplace_back("end_object()");
-        return true;
-    }
-
-    bool start_array(std::size_t elements) override
-    {
-        if (elements == (std::numeric_limits<std::size_t>::max)())
-        {
-            events.emplace_back("start_array()");
-        }
-        else
-        {
-            events.push_back("start_array(" + std::to_string(elements) + ")");
-        }
-        return true;
-    }
-
-    bool end_array() override
-    {
-        events.emplace_back("end_array()");
-        return true;
-    }
-
-    bool parse_error(std::size_t position, const std::string& /*last_token*/, const json::exception& /*ex*/) override
-    {
-        errored = true;
-        events.push_back("parse_error(" + std::to_string(position) + ")");
-        return false;
-    }
-
-    std::vector<std::string> events {}; // NOLINT(readability-redundant-member-init)
-    bool errored = false;
-};
-
-struct SaxEventLoggerExitAfterStartObject : public SaxEventLogger
-{
-    bool start_object(std::size_t elements) override
-    {
-        if (elements == (std::numeric_limits<std::size_t>::max)())
-        {
-            events.emplace_back("start_object()");
-        }
-        else
-        {
-            events.push_back("start_object(" + std::to_string(elements) + ")");
-        }
-        return false;
-    }
-};
-
-struct SaxEventLoggerExitAfterKey : public SaxEventLogger
-{
-    bool key(std::string& val) override
-    {
-        events.push_back("key(" + val + ")");
-        return false;
-    }
-};
-
-struct SaxEventLoggerExitAfterStartArray : public SaxEventLogger
-{
-    bool start_array(std::size_t elements) override
-    {
-        if (elements == (std::numeric_limits<std::size_t>::max)())
-        {
-            events.emplace_back("start_array()");
-        }
-        else
-        {
-            events.push_back("start_array(" + std::to_string(elements) + ")");
-        }
-        return false;
-    }
-};
-} // namespace utils
-
-#if defined(__clang__)
-    #pragma clang diagnostic pop
-#endif

tests/src/unit-cbor.cpp

@@ -28,6 +28,7 @@ using nlohmann::json;
 #include "make_test_data_available.hpp"
 #include "round_trip_corpus.hpp"
 #include "test_utils.hpp"
+#include "custom_object_key_type.hpp"
 #include "sax_countdown.hpp"
 using utils::SaxCountdown;
 
@@ -3357,3 +3358,55 @@ TEST_CASE("CBOR large strings and binaries (chunked reader)")
         }
     }
 }
+
+TEST_CASE("CBOR supports custom object key types")
+{
+    using custom_json = custom_object_key_test::json;
+    using custom_key = custom_object_key_test::key;
+
+    custom_json::object_t object;
+    object.emplace(custom_key{"short"}, 1);
+    object.emplace(
+              custom_key{"a key longer than twenty-three characters"},
+              2);
+
+    const custom_json value(std::move(object));
+    const auto encoded = custom_json::to_cbor(value);
+
+    CHECK(nlohmann::json::from_cbor(encoded) == nlohmann::json
+    {
+        {"short", 1},
+        {"a key longer than twenty-three characters", 2}
+    });
+}
+
+TEST_CASE("CBOR supports custom object key types nested deeper than the recursion depth limit")
+{
+    // below detail::recursion_depth_limit(), keys are written by
+    // write_cbor_iterative instead of write_cbor
+    using custom_json = custom_object_key_test::json;
+    using custom_key = custom_object_key_test::key;
+
+    const std::size_t depth = nlohmann::detail::recursion_depth_limit() + 10;
+
+    custom_json value = 1;
+    nlohmann::json expected = 1;
+    for (std::size_t i = 0; i < depth; ++i)
+    {
+        // alternate short keys with ones long enough to need a length byte
+        const std::string name = (i % 2 == 0) ? "k" + std::to_string(i)
+                                 : "a key longer than thirty-one characters " + std::to_string(i);
+
+        custom_json::object_t object;
+        object.emplace(custom_key{name}, std::move(value));
+        value = custom_json(std::move(object));
+
+        nlohmann::json::object_t expected_object;
+        expected_object.emplace(name, std::move(expected));
+        expected = nlohmann::json(std::move(expected_object));
+    }
+
+    const auto encoded = custom_json::to_cbor(value);
+    CHECK(encoded == nlohmann::json::to_cbor(expected));
+    CHECK(nlohmann::json::from_cbor(encoded) == expected);
+}

tests/src/unit-class_parser.cpp

@@ -37,15 +37,194 @@ using nlohmann::json;
 #include <utility>
 #include <vector>
 
-#include "sax_countdown.hpp"
-#include "sax_event_loggers.hpp"
 #include "test_utils.hpp"
 
-using utils::SaxCountdown;
-using utils::SaxEventLogger;
-
 namespace
 {
+class SaxEventLogger
+{
+  public:
+    bool null()
+    {
+        events.emplace_back("null()");
+        return true;
+    }
+
+    bool boolean(bool val)
+    {
+        events.emplace_back(val ? "boolean(true)" : "boolean(false)");
+        return true;
+    }
+
+    bool number_integer(json::number_integer_t val)
+    {
+        events.push_back("number_integer(" + std::to_string(val) + ")");
+        return true;
+    }
+
+    bool number_unsigned(json::number_unsigned_t val)
+    {
+        events.push_back("number_unsigned(" + std::to_string(val) + ")");
+        return true;
+    }
+
+    bool number_float(json::number_float_t /*unused*/, const std::string& s)
+    {
+        events.push_back("number_float(" + s + ")");
+        return true;
+    }
+
+    bool string(std::string& val)
+    {
+        events.push_back("string(" + val + ")");
+        return true;
+    }
+
+    bool binary(json::binary_t& val)
+    {
+        std::string binary_contents = "binary(";
+        std::string comma_space;
+        for (auto b : val)
+        {
+            binary_contents.append(comma_space);
+            binary_contents.append(std::to_string(static_cast<int>(b)));
+            comma_space = ", ";
+        }
+        binary_contents.append(")");
+        events.push_back(binary_contents);
+        return true;
+    }
+
+    bool start_object(std::size_t elements)
+    {
+        if (elements == (std::numeric_limits<std::size_t>::max)())
+        {
+            events.emplace_back("start_object()");
+        }
+        else
+        {
+            events.push_back("start_object(" + std::to_string(elements) + ")");
+        }
+        return true;
+    }
+
+    bool key(std::string& val)
+    {
+        events.push_back("key(" + val + ")");
+        return true;
+    }
+
+    bool end_object()
+    {
+        events.emplace_back("end_object()");
+        return true;
+    }
+
+    bool start_array(std::size_t elements)
+    {
+        if (elements == (std::numeric_limits<std::size_t>::max)())
+        {
+            events.emplace_back("start_array()");
+        }
+        else
+        {
+            events.push_back("start_array(" + std::to_string(elements) + ")");
+        }
+        return true;
+    }
+
+    bool end_array()
+    {
+        events.emplace_back("end_array()");
+        return true;
+    }
+
+    bool parse_error(std::size_t position, const std::string& /*unused*/, const json::exception& /*unused*/)
+    {
+        errored = true;
+        events.push_back("parse_error(" + std::to_string(position) + ")");
+        return false;
+    }
+
+    std::vector<std::string> events {}; // NOLINT(readability-redundant-member-init)
+    bool errored = false;
+};
+
+class SaxCountdown : public nlohmann::json::json_sax_t
+{
+  public:
+    explicit SaxCountdown(const int count) : events_left(count)
+    {}
+
+    bool null() override
+    {
+        return events_left-- > 0;
+    }
+
+    bool boolean(bool /*val*/) override
+    {
+        return events_left-- > 0;
+    }
+
+    bool number_integer(json::number_integer_t /*val*/) override
+    {
+        return events_left-- > 0;
+    }
+
+    bool number_unsigned(json::number_unsigned_t /*val*/) override
+    {
+        return events_left-- > 0;
+    }
+
+    bool number_float(json::number_float_t /*val*/, const std::string& /*s*/) override
+    {
+        return events_left-- > 0;
+    }
+
+    bool string(std::string& /*val*/) override
+    {
+        return events_left-- > 0;
+    }
+
+    bool binary(json::binary_t& /*val*/) override
+    {
+        return events_left-- > 0;
+    }
+
+    bool start_object(std::size_t /*elements*/) override
+    {
+        return events_left-- > 0;
+    }
+
+    bool key(std::string& /*val*/) override
+    {
+        return events_left-- > 0;
+    }
+
+    bool end_object() override
+    {
+        return events_left-- > 0;
+    }
+
+    bool start_array(std::size_t /*elements*/) override
+    {
+        return events_left-- > 0;
+    }
+
+    bool end_array() override
+    {
+        return events_left-- > 0;
+    }
+
+    bool parse_error(std::size_t /*position*/, const std::string& /*last_token*/, const json::exception& /*ex*/) override
+    {
+        return false;
+    }
+
+  private:
+    int events_left = 0;
+};
+
 json parser_helper(const std::string& s);
 bool accept_helper(const std::string& s);
 void comments_helper(const std::string& s);

tests/src/unit-custom-object-key-type.cpp

@@ -0,0 +1,501 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#include "doctest_compatibility.h"
+
+#include <nlohmann/json.hpp>
+
+#include <cstddef>
+#include <cstdint>
+#include <map>
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+// Object types with a user-defined key type. The key types differ in what they
+// offer to the library: a conversion to std::string (implicit or explicit), a
+// comparison with ==, a to_json overload, or a c_str() member.
+
+namespace custom_key_test
+{
+class key_base
+{
+  public:
+    key_base() = default;
+
+    key_base(const char* value)
+        : m_value(value)
+    {}
+
+    key_base(std::string value)
+        : m_value(std::move(value))
+    {}
+
+    // Required by JSON_DIAGNOSTICS, which reads object keys through data()
+    // when building the path of an exception.
+    const char* data() const noexcept
+    {
+        return m_value.data();
+    }
+
+    friend bool operator<(const key_base& lhs, const key_base& rhs)
+    {
+        return lhs.m_value < rhs.m_value;
+    }
+
+  protected:
+    std::string m_value;
+};
+
+// implicit conversion to std::string and operator==
+class key_full : public key_base
+{
+  public:
+    key_full() = default;
+    using key_base::key_base;
+
+    operator std::string() const
+    {
+        return m_value;
+    }
+
+    friend bool operator==(const key_full& lhs, const key_full& rhs)
+    {
+        return lhs.m_value == rhs.m_value;
+    }
+};
+
+// implicit conversion to std::string, but no operator==
+class key_no_eq : public key_base
+{
+  public:
+    key_no_eq() = default;
+    using key_base::key_base;
+
+    operator std::string() const
+    {
+        return m_value;
+    }
+};
+
+// explicit conversion to std::string, no operator==
+class key_explicit : public key_base
+{
+  public:
+    key_explicit() = default;
+    using key_base::key_base;
+
+    explicit operator std::string() const
+    {
+        return m_value;
+    }
+};
+
+// no conversion at all, only a to_json overload, no operator==
+class key_to_json : public key_base
+{
+  public:
+    key_to_json() = default;
+    using key_base::key_base;
+
+    const std::string& value() const
+    {
+        return m_value;
+    }
+};
+
+template<typename BasicJsonType>
+void to_json(BasicJsonType& j, const key_to_json& k)
+{
+    j = k.value();
+}
+
+// like key_to_json, but with size() and c_str()
+class key_c_str : public key_base
+{
+  public:
+    key_c_str() = default;
+    using key_base::key_base;
+
+    const std::string& value() const
+    {
+        return m_value;
+    }
+
+    std::size_t size() const
+    {
+        return m_value.size();
+    }
+
+    const char* c_str() const
+    {
+        return m_value.c_str();
+    }
+};
+
+template<typename BasicJsonType>
+void to_json(BasicJsonType& j, const key_c_str& k)
+{
+    j = k.value();
+}
+
+// std::map with key type K, ignoring the key type basic_json passes
+template<class K>
+struct object_for
+{
+    template<class Key, class Value, class Compare, class Allocator>
+    using pair_allocator = typename std::allocator_traits<Allocator>::template rebind_alloc<std::pair<const K, Value>>;
+
+    template<class Key, class Value, class Compare, class Allocator>
+    using type = std::map<K, Value, std::less<K>, pair_allocator<Key, Value, Compare, Allocator>>; // NOLINT(modernize-use-transparent-functors)
+};
+
+using json_full = nlohmann::json::with_object_t<object_for<key_full>::type>;
+using json_no_eq = nlohmann::json::with_object_t<object_for<key_no_eq>::type>;
+using json_explicit = nlohmann::json::with_object_t<object_for<key_explicit>::type>;
+using json_to_json = nlohmann::json::with_object_t<object_for<key_to_json>::type>;
+using json_c_str = nlohmann::json::with_object_t<object_for<key_c_str>::type>;
+
+// a key that is long enough to need a length byte in CBOR and MessagePack
+const char* long_key_name(std::size_t i, std::string& storage);
+const char* long_key_name(std::size_t i, std::string& storage)
+{
+    storage = "a key longer than thirty-one characters " + std::to_string(i);
+    return storage.c_str();
+}
+
+// name of the key at nesting level i of a deep value
+std::string deep_name(std::size_t i, bool long_keys);
+std::string deep_name(std::size_t i, bool long_keys)
+{
+    std::string storage;
+    return (long_keys && i % 2 == 1) ? std::string(long_key_name(i, storage)) : "k" + std::to_string(i);
+}
+
+// {"a": 1, "b": [true, null, "x"], "c": {"d": 2.5}, <keys of 23, 36, and 300 characters>}
+// 23 is the longest CBOR length stored in the initial byte; 36 needs one
+// length byte in CBOR and MessagePack, 300 needs two
+template<class J>
+J make_shallow()
+{
+    using key_t = typename J::object_t::key_type;
+
+    J array = J::array();
+    array.push_back(J(true));
+    array.push_back(J(nullptr));
+    array.push_back(J("x"));
+
+    typename J::object_t inner;
+    inner.emplace(key_t("d"), J(2.5));
+
+    typename J::object_t object;
+    object.emplace(key_t("a"), J(1));
+    object.emplace(key_t("b"), std::move(array));
+    object.emplace(key_t("c"), J(std::move(inner)));
+    object.emplace(key_t(std::string(23, 'x')), J(2));
+    object.emplace(key_t(std::string(36, 'y')), J(3));
+    object.emplace(key_t(std::string(300, 'z')), J(4));
+    return J(std::move(object));
+}
+
+// {"k0": {"k1": {... {"k<depth-1>": 1} ...}}}
+template<class J>
+J make_deep(std::size_t depth, bool long_keys)
+{
+    using key_t = typename J::object_t::key_type;
+
+    J value = 1;
+    for (std::size_t i = depth; i > 0; --i)
+    {
+        typename J::object_t object;
+        object.emplace(key_t(deep_name(i - 1, long_keys)), std::move(value));
+        value = J(std::move(object));
+    }
+    return value;
+}
+
+std::size_t deep_depth();
+std::size_t deep_depth()
+{
+    return nlohmann::detail::recursion_depth_limit() + 10;
+}
+
+// walk down the nesting levels without recursion and check the leaf
+template<class J>
+bool check_deep(const J& value, std::size_t depth, bool long_keys)
+{
+    using key_t = typename J::object_t::key_type;
+
+    const J* current = &value;
+    for (std::size_t i = 0; i < depth; ++i)
+    {
+        if (!current->is_object() || current->size() != 1)
+        {
+            return false;
+        }
+        const auto it = current->find(key_t(deep_name(i, long_keys)));
+        if (it == current->end())
+        {
+            return false;
+        }
+        current = &it.value();
+    }
+    return current->is_number_integer() && current->template get<int>() == 1;
+}
+
+template<class J>
+bool check_shallow(const J& value)
+{
+    using key_t = typename J::object_t::key_type;
+
+    if (!value.is_object() || value.size() != 6)
+    {
+        return false;
+    }
+
+    const auto a = value.find(key_t("a"));
+    const auto b = value.find(key_t("b"));
+    const auto c = value.find(key_t("c"));
+    if (a == value.end() || b == value.end() || c == value.end())
+    {
+        return false;
+    }
+
+    const auto d = c->find(key_t("d"));
+    // basic_json::operator== needs operator== on the keys, which most of the
+    // key types do not have, so the values are checked through get<>()
+    return a->template get<int>() == 1
+    && b->is_array() && b->size() == 3 && (*b)[0].template get<bool>() && (*b)[1].is_null()
+    && (*b)[2].template get<std::string>() == "x"
+    && d != c->end() && d->template get<double>() == 2.5
+    && value.find(key_t(std::string(23, 'x')))->template get<int>() == 2
+    && value.find(key_t(std::string(36, 'y')))->template get<int>() == 3
+    && value.find(key_t(std::string(300, 'z')))->template get<int>() == 4;
+}
+
+template<class J>
+bool is_missing(const J& value, const char* name)
+{
+    return value.find(typename J::object_t::key_type(name)) == value.end();
+}
+
+// member access through find(): at() does not compile for key types without
+// size() or a conversion to string_t (key_to_json), as in version 3.12.0
+template<class J>
+const J& member(const J& value, const char* name)
+{
+    const auto it = value.find(typename J::object_t::key_type(name));
+    REQUIRE(it != value.end());
+    return *it;
+}
+} // namespace custom_key_test
+
+TEST_CASE_TEMPLATE("custom object key types: copy", J,
+                   custom_key_test::json_full, custom_key_test::json_no_eq, custom_key_test::json_explicit,
+                   custom_key_test::json_to_json, custom_key_test::json_c_str)
+{
+    SECTION("shallow")
+    {
+        const J original = custom_key_test::make_shallow<J>();
+        REQUIRE(custom_key_test::check_shallow(original));
+
+        const J copy(original); // NOLINT(performance-unnecessary-copy-initialization)
+        CHECK(custom_key_test::check_shallow(copy));
+
+        J assigned;
+        assigned = original;
+        CHECK(custom_key_test::check_shallow(assigned));
+
+        // the original is unchanged
+        CHECK(custom_key_test::check_shallow(original));
+    }
+
+    SECTION("deep")
+    {
+        const std::size_t depth = custom_key_test::deep_depth();
+
+        const J original = custom_key_test::make_deep<J>(depth, false);
+        REQUIRE(custom_key_test::check_deep(original, depth, false));
+
+        const J copy(original); // NOLINT(performance-unnecessary-copy-initialization)
+        CHECK(custom_key_test::check_deep(copy, depth, false));
+
+        J assigned;
+        assigned = original;
+        CHECK(custom_key_test::check_deep(assigned, depth, false));
+
+        CHECK(custom_key_test::check_deep(original, depth, false));
+    }
+}
+
+TEST_CASE_TEMPLATE("custom object key types: parse", J,
+                   custom_key_test::json_full, custom_key_test::json_no_eq, custom_key_test::json_explicit,
+                   custom_key_test::json_to_json, custom_key_test::json_c_str)
+{
+    const J j = J::parse(R"({"a":1,"b":{"c":[1,2]}})");
+
+    CHECK(j.size() == 2);
+    CHECK(custom_key_test::member(j, "a").template get<int>() == 1);
+    CHECK(custom_key_test::member(custom_key_test::member(j, "b"), "c").size() == 2);
+    CHECK(custom_key_test::member(custom_key_test::member(j, "b"), "c")[1].template get<int>() == 2);
+
+    // a deeply nested document
+    const std::size_t depth = custom_key_test::deep_depth();
+    std::string text;
+    for (std::size_t i = 0; i < depth; ++i)
+    {
+        text += "{\"k" + std::to_string(i) + "\":";
+    }
+    text += "1";
+    text.append(depth, '}');
+    CHECK(custom_key_test::check_deep(J::parse(text), depth, false));
+}
+
+TEST_CASE_TEMPLATE("custom object key types: merge_patch, update, and insert", J,
+                   custom_key_test::json_full, custom_key_test::json_no_eq, custom_key_test::json_explicit,
+                   custom_key_test::json_to_json, custom_key_test::json_c_str)
+{
+    SECTION("merge_patch")
+    {
+        J j = J::parse(R"({"a":1,"b":2,"n":{"x":1,"y":2}})");
+        j.merge_patch(J::parse(R"({"b":null,"c":3,"n":{"y":null,"z":3}})"));
+
+        CHECK(j.size() == 3);
+        CHECK(custom_key_test::member(j, "a").template get<int>() == 1);
+        CHECK(custom_key_test::is_missing(j, "b"));
+        CHECK(custom_key_test::member(j, "c").template get<int>() == 3);
+        CHECK(custom_key_test::member(j, "n").size() == 2);
+        CHECK(custom_key_test::member(custom_key_test::member(j, "n"), "x").template get<int>() == 1);
+        CHECK(custom_key_test::member(custom_key_test::member(j, "n"), "z").template get<int>() == 3);
+    }
+
+    SECTION("update")
+    {
+        J j = J::parse(R"({"a":1,"b":2,"n":{"x":1}})");
+        const J other = J::parse(R"({"b":3,"c":4,"n":{"y":2}})");
+
+        J replaced = j;
+        replaced.update(other);
+        CHECK(replaced.size() == 4);
+        CHECK(custom_key_test::member(replaced, "a").template get<int>() == 1);
+        CHECK(custom_key_test::member(replaced, "b").template get<int>() == 3);
+        CHECK(custom_key_test::member(replaced, "c").template get<int>() == 4);
+        CHECK(custom_key_test::member(replaced, "n").size() == 1);
+        CHECK(custom_key_test::member(custom_key_test::member(replaced, "n"), "y").template get<int>() == 2);
+
+        j.update(other, true);
+        CHECK(j.size() == 4);
+        CHECK(custom_key_test::member(j, "n").size() == 2);
+        CHECK(custom_key_test::member(custom_key_test::member(j, "n"), "x").template get<int>() == 1);
+        CHECK(custom_key_test::member(custom_key_test::member(j, "n"), "y").template get<int>() == 2);
+    }
+
+    SECTION("insert")
+    {
+        J j = J::parse(R"({"a":1,"b":2})");
+        const J other = J::parse(R"({"b":3,"c":4})");
+        j.insert(other.begin(), other.end());
+
+        CHECK(j.size() == 3);
+        CHECK(custom_key_test::member(j, "b").template get<int>() == 2);
+        CHECK(custom_key_test::member(j, "c").template get<int>() == 4);
+    }
+}
+
+TEST_CASE_TEMPLATE("custom object key types: at() reports a missing key", J,
+                   custom_key_test::json_full, custom_key_test::json_no_eq, custom_key_test::json_explicit,
+                   custom_key_test::json_c_str)
+{
+    // not for key_to_json: at() needs the key's size() or a conversion to
+    // string_t for its error message, which also was the case in version 3.12.0
+    J j = J::parse(R"({"a":1})");
+    const J& j_const = j;
+
+    CHECK(j.at("a").template get<int>() == 1);
+    CHECK(j_const.at("a").template get<int>() == 1);
+    CHECK_THROWS_WITH_AS(j.at("missing"), "[json.exception.out_of_range.403] key 'missing' not found", typename J::out_of_range&);
+    CHECK_THROWS_WITH_AS(j_const.at("missing"), "[json.exception.out_of_range.403] key 'missing' not found", typename J::out_of_range&);
+}
+
+TEST_CASE_TEMPLATE("custom object key types: BSON", J,
+                   custom_key_test::json_full, custom_key_test::json_no_eq)
+{
+    SECTION("shallow")
+    {
+        const J value = custom_key_test::make_shallow<J>();
+        const nlohmann::json expected = custom_key_test::make_shallow<nlohmann::json>();
+
+        const std::vector<std::uint8_t> encoded = J::to_bson(value);
+        CHECK(encoded == nlohmann::json::to_bson(expected));
+        CHECK(nlohmann::json::from_bson(encoded) == expected);
+    }
+
+    SECTION("deep")
+    {
+        const std::size_t depth = custom_key_test::deep_depth();
+        const J value = custom_key_test::make_deep<J>(depth, false);
+        const nlohmann::json expected = custom_key_test::make_deep<nlohmann::json>(depth, false);
+
+        const std::vector<std::uint8_t> encoded = J::to_bson(value);
+        CHECK(encoded == nlohmann::json::to_bson(expected));
+        CHECK(nlohmann::json::from_bson(encoded) == expected);
+    }
+}
+
+TEST_CASE_TEMPLATE("custom object key types: CBOR", J,
+                   custom_key_test::json_full, custom_key_test::json_no_eq, custom_key_test::json_explicit,
+                   custom_key_test::json_to_json, custom_key_test::json_c_str)
+{
+    SECTION("shallow")
+    {
+        const J value = custom_key_test::make_shallow<J>();
+        const nlohmann::json expected = custom_key_test::make_shallow<nlohmann::json>();
+
+        const std::vector<std::uint8_t> encoded = J::to_cbor(value);
+        CHECK(encoded == nlohmann::json::to_cbor(expected));
+        CHECK(nlohmann::json::from_cbor(encoded) == expected);
+    }
+
+    SECTION("deeper than the recursion depth limit")
+    {
+        const std::size_t depth = custom_key_test::deep_depth();
+        const J value = custom_key_test::make_deep<J>(depth, true);
+        const nlohmann::json expected = custom_key_test::make_deep<nlohmann::json>(depth, true);
+
+        const std::vector<std::uint8_t> encoded = J::to_cbor(value);
+        CHECK(encoded == nlohmann::json::to_cbor(expected));
+        CHECK(nlohmann::json::from_cbor(encoded) == expected);
+    }
+}
+
+TEST_CASE_TEMPLATE("custom object key types: MessagePack", J,
+                   custom_key_test::json_full, custom_key_test::json_no_eq, custom_key_test::json_explicit,
+                   custom_key_test::json_to_json, custom_key_test::json_c_str)
+{
+    SECTION("shallow")
+    {
+        const J value = custom_key_test::make_shallow<J>();
+        const nlohmann::json expected = custom_key_test::make_shallow<nlohmann::json>();
+
+        const std::vector<std::uint8_t> encoded = J::to_msgpack(value);
+        CHECK(encoded == nlohmann::json::to_msgpack(expected));
+        CHECK(nlohmann::json::from_msgpack(encoded) == expected);
+    }
+
+    SECTION("deeper than the recursion depth limit")
+    {
+        const std::size_t depth = custom_key_test::deep_depth();
+        const J value = custom_key_test::make_deep<J>(depth, true);
+        const nlohmann::json expected = custom_key_test::make_deep<nlohmann::json>(depth, true);
+
+        const std::vector<std::uint8_t> encoded = J::to_msgpack(value);
+        CHECK(encoded == nlohmann::json::to_msgpack(expected));
+        CHECK(nlohmann::json::from_msgpack(encoded) == expected);
+    }
+}

tests/src/unit-deserialization.cpp

@@ -36,15 +36,155 @@ using nlohmann::json;
 #include <string>
 #include <valarray>
 
-#include "sax_event_loggers.hpp"
-
-using utils::SaxEventLogger;
-using utils::SaxEventLoggerExitAfterKey;
-using utils::SaxEventLoggerExitAfterStartArray;
-using utils::SaxEventLoggerExitAfterStartObject;
-
 namespace
 {
+struct SaxEventLogger : public nlohmann::json_sax<json>
+{
+    bool null() override
+    {
+        events.emplace_back("null()");
+        return true;
+    }
+
+    bool boolean(bool val) override
+    {
+        events.emplace_back(val ? "boolean(true)" : "boolean(false)");
+        return true;
+    }
+
+    bool number_integer(json::number_integer_t val) override
+    {
+        events.push_back("number_integer(" + std::to_string(val) + ")");
+        return true;
+    }
+
+    bool number_unsigned(json::number_unsigned_t val) override
+    {
+        events.push_back("number_unsigned(" + std::to_string(val) + ")");
+        return true;
+    }
+
+    bool number_float(json::number_float_t /*val*/, const std::string& s) override
+    {
+        events.push_back("number_float(" + s + ")");
+        return true;
+    }
+
+    bool string(std::string& val) override
+    {
+        events.push_back("string(" + val + ")");
+        return true;
+    }
+
+    bool binary(json::binary_t& val) override
+    {
+        std::string binary_contents = "binary(";
+        std::string comma_space;
+        for (auto b : val)
+        {
+            binary_contents.append(comma_space);
+            binary_contents.append(std::to_string(static_cast<int>(b)));
+            comma_space = ", ";
+        }
+        binary_contents.append(")");
+        events.push_back(binary_contents);
+        return true;
+    }
+
+    bool start_object(std::size_t elements) override
+    {
+        if (elements == (std::numeric_limits<std::size_t>::max)())
+        {
+            events.emplace_back("start_object()");
+        }
+        else
+        {
+            events.push_back("start_object(" + std::to_string(elements) + ")");
+        }
+        return true;
+    }
+
+    bool key(std::string& val) override
+    {
+        events.push_back("key(" + val + ")");
+        return true;
+    }
+
+    bool end_object() override
+    {
+        events.emplace_back("end_object()");
+        return true;
+    }
+
+    bool start_array(std::size_t elements) override
+    {
+        if (elements == (std::numeric_limits<std::size_t>::max)())
+        {
+            events.emplace_back("start_array()");
+        }
+        else
+        {
+            events.push_back("start_array(" + std::to_string(elements) + ")");
+        }
+        return true;
+    }
+
+    bool end_array() override
+    {
+        events.emplace_back("end_array()");
+        return true;
+    }
+
+    bool parse_error(std::size_t position, const std::string& /*last_token*/, const json::exception& /*ex*/) override
+    {
+        events.push_back("parse_error(" + std::to_string(position) + ")");
+        return false;
+    }
+
+    std::vector<std::string> events {}; // NOLINT(readability-redundant-member-init)
+};
+
+struct SaxEventLoggerExitAfterStartObject : public SaxEventLogger
+{
+    bool start_object(std::size_t elements) override
+    {
+        if (elements == (std::numeric_limits<std::size_t>::max)())
+        {
+            events.emplace_back("start_object()");
+        }
+        else
+        {
+            events.push_back("start_object(" + std::to_string(elements) + ")");
+        }
+        return false;
+    }
+};
+
+struct SaxEventLoggerExitAfterKey : public SaxEventLogger
+{
+    bool key(std::string& val) override
+    {
+        events.push_back("key(" + val + ")");
+        return false;
+    }
+};
+
+struct SaxEventLoggerExitAfterStartArray : public SaxEventLogger
+{
+    bool start_array(std::size_t elements) override
+    {
+        if (elements == (std::numeric_limits<std::size_t>::max)())
+        {
+            events.emplace_back("start_array()");
+        }
+        else
+        {
+            events.push_back("start_array(" + std::to_string(elements) + ")");
+        }
+        return false;
+    }
+};
+
 template <typename T>
 class proxy_iterator
 {

tests/src/unit-msgpack.cpp

@@ -31,6 +31,7 @@ using nlohmann::json;
 #include "make_test_data_available.hpp"
 #include "round_trip_corpus.hpp"
 #include "test_utils.hpp"
+#include "custom_object_key_type.hpp"
 #include "sax_countdown.hpp"
 using utils::SaxCountdown;
 
@@ -2522,3 +2523,55 @@ TEST_CASE("MessagePack large strings and binaries (chunked reader)")
         }
     }
 }
+
+TEST_CASE("MessagePack supports custom object key types")
+{
+    using custom_json = custom_object_key_test::json;
+    using custom_key = custom_object_key_test::key;
+
+    custom_json::object_t object;
+    object.emplace(custom_key{"short"}, 1);
+    object.emplace(
+              custom_key{"a key longer than thirty-one characters"},
+              2);
+
+    const custom_json value(std::move(object));
+    const auto encoded = custom_json::to_msgpack(value);
+
+    CHECK(nlohmann::json::from_msgpack(encoded) == nlohmann::json
+    {
+        {"short", 1},
+        {"a key longer than thirty-one characters", 2}
+    });
+}
+
+TEST_CASE("MessagePack supports custom object key types nested deeper than the recursion depth limit")
+{
+    // below detail::recursion_depth_limit(), keys are written by
+    // write_msgpack_iterative instead of write_msgpack
+    using custom_json = custom_object_key_test::json;
+    using custom_key = custom_object_key_test::key;
+
+    const std::size_t depth = nlohmann::detail::recursion_depth_limit() + 10;
+
+    custom_json value = 1;
+    nlohmann::json expected = 1;
+    for (std::size_t i = 0; i < depth; ++i)
+    {
+        // alternate short keys with ones long enough to need a length byte
+        const std::string name = (i % 2 == 0) ? "k" + std::to_string(i)
+                                 : "a key longer than thirty-one characters " + std::to_string(i);
+
+        custom_json::object_t object;
+        object.emplace(custom_key{name}, std::move(value));
+        value = custom_json(std::move(object));
+
+        nlohmann::json::object_t expected_object;
+        expected_object.emplace(name, std::move(expected));
+        expected = nlohmann::json(std::move(expected_object));
+    }
+
+    const auto encoded = custom_json::to_msgpack(value);
+    CHECK(encoded == nlohmann::json::to_msgpack(expected));
+    CHECK(nlohmann::json::from_msgpack(encoded) == expected);
+}