Fix CI on develop after merging the ready-to-merge PRs (#5754)

* Keep the serializer conversion for objects whose keys cannot be converted

#5591 added a test converting nlohmann::json into a basic_json whose
string type cannot be constructed from std::string. That instantiates
convert_iteratively(), whose members.emplace_back(next.key(), ...) needs
exactly that key conversion, and broke the build of unit-alt-string.
Dispatch on the key's constructibility and leave such conversions to the
serializers, as the levels above the nesting bound already do (#3425).

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

* Fix the remaining CI failures on develop

- unit-wstring: with a 16-bit wchar_t (Windows), a lone surrogate is
  reported as the ill-formed byte 0xFF since #5704; the std::wstring
  expectations still had the previous <U+0000>.
- ci_single_binaries: json_literals.hpp (#5610) and json.hpp include each
  other on purpose, and IWYU, not following the cycle, asks to replace
  json.hpp with json_fwd.hpp. Report its findings without failing the
  build, as already done for json.hpp.

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

* Fix the library warnings and noexcept specifications from the merged PRs

- binary_reader: rename the error_handler constructor parameter, which
  shadowed the member (-Wshadow, -Wshadow-field-in-constructor; #5746)
- basic_json(copy_construct_tag, ...): declare it noexcept when copying
  the base class is (GCC 16 -Wnoexcept; #5690)
- the scalar-on-left legacy comparison operators: noexcept only when
  converting the scalar is, like their member counterparts (#5682, #5751)
- compare_leaves: use std::is_eq/is_lt/is_gt instead of comparing a
  std::partial_ordering with 0 (-Wzero-as-null-pointer-constant; #5686)
- serializer: silence MSVC C4127 for the EnsureAscii template parameter
  (#5741, #5746)
- clang-tidy: return the sanitized reference in binary_writer, take the
  key of ordered_map::find_impl by const reference (#5727), and mark the
  switches over parse_array_index (#5728)
- ordered_map: keep <memory> for std::allocator (IWYU)

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

* Split unit-conversions.cpp so MinGW can link it

clang 18 with the MinGW linker failed to link test-conversions_cpp17
("relocation truncated to fit: IMAGE_REL_AMD64_REL32"). As windows.yml
recommends, keep the objects small by splitting the test file.

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

* Fix the tests added by the merged PRs for all CI configurations

- discard the results of dump() and from_*() in CHECK_THROWS with
  utils::ignore_return_value (GCC -Werror=unused-result)
- give unit-bson's huge_string_t a default constructor (MSVC C2512,
  GCC 5, clang 3.5)
- unit-disabled_exceptions: use the literals namespace when the global
  UDLs are off (ci_test_noglobaludls; #5700)
- unit-binary_utf8_strict: expect the JSON pointer prefix with
  JSON_DIAGNOSTICS (#5741)
- skip the tests that rely on exceptions under JSON_NOEXCEPTION
  (#5678, #5732)
- clang-tidy and clang -Werror: static test data, CAPTURE(...);,
  const-correctness, use-after-move alias, unused conversion operator,
  a missing <iterator> include

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

* Title the macro examples and add JSON_STRICT_BINARY_UTF8 to the docset

The documentation style check requires "Example: ..." titles on pages with several examples (#5741, #5591) and a docset entry for every macro page.

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

* Regenerate BUILD.bazel and nlohmann_json.natvis

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

#5746 added detail/output/error_handler.hpp and #5741 the json_abi_sbu8 ABI tag.

* Install libidn11 for the CMake 3.5.0 binary in ci_cmake_flags

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

#5733 moved ci_cmake_options from ubuntu:focal to ubuntu:24.04, which no longer ships libidn.so.11; the CMake 3.5.0 release binary links against it, so every ci_cmake_flags run has failed since. Install focal's libidn11 package for that matrix entry only.

* Suppress Infer's false STACK_VARIABLE_ADDRESS_ESCAPE in get_impl

get_impl() returns its local by value. A test added by the merged PRs instantiates it with a type Infer misreads, so ci_infer reported the 2021 code for the first time.

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

---------

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

include/nlohmann/detail/input/binary_reader.hpp

@@ -110,15 +110,15 @@ class binary_reader
 
     @param[in] adapter  input adapter to read from
     @param[in] format   the binary format to parse
-    @param[in] error_handler  how to treat text strings and object keys that
+    @param[in] error_handler_  how to treat text strings and object keys that
                are not well-formed UTF-8; none of the supported formats
                requires a decoder to reject those, so the default is to
                @ref error_handler_t::keep them unchanged, as every binary
                reader did before this parameter existed
     */
     explicit binary_reader(InputAdapterType&& adapter, const input_format_t format = input_format_t::json,
-                           const error_handler_t error_handler = error_handler_t::keep) noexcept
-        : ia(std::move(adapter)), input_format(format), error_handler(error_handler)
+                           const error_handler_t error_handler_ = error_handler_t::keep) noexcept
+        : ia(std::move(adapter)), input_format(format), error_handler(error_handler_)
     {
         (void)detail::is_sax_static_asserts<SAX, BasicJsonType> {};
     }

include/nlohmann/detail/json_pointer.hpp

@@ -322,6 +322,8 @@ class json_pointer
         typename BasicJsonType::size_type idx{};
         switch (parse_array_index<BasicJsonType>(s, idx))
         {
+            // 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(106, 0, detail::concat("array index '", s, "' must not begin with '0'"), nullptr));
             case array_index_status::not_a_number:
@@ -685,6 +687,8 @@ class json_pointer
                     typename BasicJsonType::size_type idx{};
                     switch (parse_array_index<BasicJsonType>(reference_token, idx))
                     {
+                        // 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(106, 0, detail::concat("array index '", reference_token, "' must not begin with '0'"), nullptr));
                         case array_index_status::not_a_number:

include/nlohmann/detail/output/binary_writer.hpp

@@ -2260,18 +2260,18 @@ class binary_writer
         switch (error_handler)
         {
             case error_handler_t::keep:
-                return s;
+                return s; // NOLINT(bugprone-return-const-ref-from-parameter): callers pass lvalues that outlive the call
 
             case error_handler_t::strict:
                 check_utf8(s, context);
-                return s;
+                return s; // NOLINT(bugprone-return-const-ref-from-parameter): callers pass lvalues that outlive the call
 
             case error_handler_t::replace:
             case error_handler_t::ignore:
             default:
                 if (is_valid_utf8(s))
                 {
-                    return s;
+                    return s; // NOLINT(bugprone-return-const-ref-from-parameter): callers pass lvalues that outlive the call
                 }
                 storage = sanitize_utf8(s, error_handler);
                 return storage;

include/nlohmann/detail/output/serializer.hpp

@@ -706,6 +706,11 @@ class serializer
     @a ensure_ascii is a template parameter here so that the branch on it is
     resolved once, outside the loop; see @ref dump_escaped.
     */
+#ifdef JSON_HEDLEY_MSVC_VERSION
+#pragma warning(push)
+    // EnsureAscii is a template parameter; C++11 has no if constexpr
+#pragma warning(disable : 4127) // conditional expression is constant
+#endif
     template<bool EnsureAscii>
     void dump_escaped_impl(const string_t& s)
     {
@@ -1055,6 +1060,9 @@ class serializer
             }
         }
     }
+#ifdef JSON_HEDLEY_MSVC_VERSION
+#pragma warning(pop)
+#endif
 
   private:
     /*!

include/nlohmann/json.hpp

@@ -1048,6 +1048,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
           never name it to call this constructor itself.
     */
     basic_json(copy_construct_tag /*unused*/, const basic_json& src)
+    noexcept(std::is_nothrow_copy_constructible<json_base_class_t>::value)
         : json_base_class_t(src)
 #if JSON_DIAGNOSTIC_POSITIONS
         , start_position(src.start_position)
@@ -1442,7 +1443,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     be destroyed.
     */
     template<typename BasicJsonType>
-    void convert_iteratively(const BasicJsonType& val)
+    void convert_iteratively(const BasicJsonType& val, std::true_type /*unused*/)
     {
         using other_const_iterator = typename BasicJsonType::const_iterator;
 
@@ -1536,21 +1537,38 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
         if (JSON_HEDLEY_LIKELY(guard.okay()))
         {
-            // every element comes back to the converting constructor
-            if (val.is_object())
-            {
-                using other_object_t = typename BasicJsonType::object_t;
-                JSONSerializer<other_object_t>::to_json(*this, val.template get_ref<const other_object_t&>());
-            }
-            else
-            {
-                using other_array_t = typename BasicJsonType::array_t;
-                JSONSerializer<other_array_t>::to_json(*this, val.template get_ref<const other_array_t&>());
-            }
+            convert_by_serializers(val);
             return;
         }
 
-        convert_iteratively(val);
+        // the iterative conversion needs to construct this object type's keys
+        // from those of @a val; if it cannot, neither can the range constructor,
+        // and the serializers convert @a val some other way (see #3425)
+        convert_iteratively(val, std::is_constructible<typename object_t::key_type, const typename BasicJsonType::string_t&> {});
+    }
+
+    /// @brief convert the object or array @a val with the serializers; every
+    /// element comes back to the converting constructor
+    template<typename BasicJsonType>
+    void convert_by_serializers(const BasicJsonType& val)
+    {
+        if (val.is_object())
+        {
+            using other_object_t = typename BasicJsonType::object_t;
+            JSONSerializer<other_object_t>::to_json(*this, val.template get_ref<const other_object_t&>());
+        }
+        else
+        {
+            using other_array_t = typename BasicJsonType::array_t;
+            JSONSerializer<other_array_t>::to_json(*this, val.template get_ref<const other_array_t&>());
+        }
+    }
+
+    /// @brief convert @a val whose keys cannot be converted, see @ref convert_structured
+    template<typename BasicJsonType>
+    void convert_iteratively(const BasicJsonType& val, std::false_type /*unused*/)
+    {
+        convert_by_serializers(val);
     }
 
 
@@ -1624,15 +1642,15 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     static compare_result compare_leaves(const_reference lhs, const_reference rhs, std::true_type /*ordered*/) noexcept
     {
         const std::partial_ordering order = lhs <=> rhs; // *NOPAD*
-        if (order == 0)
+        if (std::is_eq(order))
         {
             return compare_result::equal;
         }
-        if (order < 0)
+        if (std::is_lt(order))
         {
             return compare_result::less;
         }
-        if (order > 0)
+        if (std::is_gt(order))
         {
             return compare_result::greater;
         }
@@ -2704,6 +2722,8 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     {
         auto ret = ValueType();
         JSONSerializer<ValueType>::from_json(*this, ret);
+        // false positive: ret is returned by value, not its address
+        // @infer-ignore STACK_VARIABLE_ADDRESS_ESCAPE
         return ret;
     }
 
@@ -5058,7 +5078,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_le/
     template<typename ScalarType>
     requires std::is_scalar_v<ScalarType>
-    friend bool operator<=(ScalarType lhs, const_reference rhs) noexcept
+    friend bool operator<=(ScalarType lhs, const_reference rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return basic_json(lhs) <= rhs;
     }
@@ -5067,7 +5087,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/operator_ge/
     template<typename ScalarType>
     requires std::is_scalar_v<ScalarType>
-    friend bool operator>=(ScalarType lhs, const_reference rhs) noexcept
+    friend bool operator>=(ScalarType lhs, const_reference rhs) noexcept(std::is_nothrow_constructible<basic_json, ScalarType>::value)
     {
         return basic_json(lhs) >= rhs;
     }

include/nlohmann/ordered_map.hpp

@@ -12,7 +12,7 @@
 #include <functional> // equal_to, less
 #include <initializer_list> // initializer_list
 #include <iterator> // input_iterator_tag, iterator_traits
-#include <memory> // allocator
+#include <memory> // allocator // IWYU pragma: keep
 #include <new> // for operator new (placement new)
 #include <stdexcept> // for out_of_range
 #include <tuple> // forward_as_tuple
@@ -78,7 +78,7 @@ private:
     /// @brief find the entry for @a key, for either constness of @a self
     /// @note the single place that performs the linear key search
     template<typename Self, typename KeyType>
-    static auto find_impl(Self& self, KeyType&& key) -> decltype(self.begin())
+    static auto find_impl(Self& self, const KeyType& key) -> decltype(self.begin())
     {
         for (auto it = self.begin(); it != self.end(); ++it)
         {