From 668fddc766b6326b0f05cd8be0a7c3ab17853d64 Mon Sep 17 00:00:00 2001
From: Niels Lohmann <mail@nlohmann.me>
Date: Wed, 30 Sep 2026 09:55:53 +0200
Subject: [PATCH] Drop serializer.hpp's dependency on binary_writer.hpp

The only use of binary_writer in serializer.hpp was
binary_writer<BasicJsonType, char>::to_char_type() to write the
U+FFFD replacement character's three bytes. With CharType=char this
is an identity conversion, so the include of binary_writer.hpp (and
transitively binary_reader.hpp) pulled in a large, unrelated header
for a no-op call.

Write the three bytes directly instead. serializer.hpp compiles
standalone with -Wall -Wextra -Werror, with and without
-funsigned-char, and unit-serialization's error_handler_t::replace
cases (with and without ensure_ascii) still pass. Moving
binary_writer's to_char_type/to_msgpack_length to its private section
is left as an optional follow-up.

Part of #5709

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---
 include/nlohmann/detail/output/serializer.hpp | 7 +++----
 single_include/nlohmann/json.hpp              | 8 +++-----
 2 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/include/nlohmann/detail/output/serializer.hpp b/include/nlohmann/detail/output/serializer.hpp
index 11f24c12f..118af5dc7 100644
--- a/include/nlohmann/detail/output/serializer.hpp
+++ b/include/nlohmann/detail/output/serializer.hpp
@@ -28,7 +28,6 @@
 #include <nlohmann/detail/input/string_scan.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
 #include <nlohmann/detail/meta/cpp_future.hpp>
-#include <nlohmann/detail/output/binary_writer.hpp>
 #include <nlohmann/detail/output/output_adapters.hpp>
 #include <nlohmann/detail/recursion_depth_limit.hpp>
 #include <nlohmann/detail/string_concat.hpp>
@@ -915,9 +914,9 @@ class serializer
                                 }
                                 else
                                 {
-                                    string_buffer[bytes++] = detail::binary_writer<BasicJsonType, char>::to_char_type('\xEF');
-                                    string_buffer[bytes++] = detail::binary_writer<BasicJsonType, char>::to_char_type('\xBF');
-                                    string_buffer[bytes++] = detail::binary_writer<BasicJsonType, char>::to_char_type('\xBD');
+                                    string_buffer[bytes++] = '\xEF';
+                                    string_buffer[bytes++] = '\xBF';
+                                    string_buffer[bytes++] = '\xBD';
                                 }
 
                                 // write buffer and reset index; there must be 13 bytes
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index e7be6d80f..b88489a5c 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -24103,8 +24103,6 @@ NLOHMANN_JSON_NAMESPACE_END
 
 // #include <nlohmann/detail/meta/cpp_future.hpp>
 
-// #include <nlohmann/detail/output/binary_writer.hpp>
-
 // #include <nlohmann/detail/output/output_adapters.hpp>
 
 // #include <nlohmann/detail/recursion_depth_limit.hpp>
@@ -24996,9 +24994,9 @@ class serializer
                                 }
                                 else
                                 {
-                                    string_buffer[bytes++] = detail::binary_writer<BasicJsonType, char>::to_char_type('\xEF');
-                                    string_buffer[bytes++] = detail::binary_writer<BasicJsonType, char>::to_char_type('\xBF');
-                                    string_buffer[bytes++] = detail::binary_writer<BasicJsonType, char>::to_char_type('\xBD');
+                                    string_buffer[bytes++] = '\xEF';
+                                    string_buffer[bytes++] = '\xBF';
+                                    string_buffer[bytes++] = '\xBD';
                                 }
 
                                 // write buffer and reset index; there must be 13 bytes