From f8df3df0213fce4ba8a40389b7dad3f8f4c5d0a1 Mon Sep 17 00:00:00 2001
From: Niels Lohmann <mail@nlohmann.me>
Date: Fri, 23 Oct 2026 22:16:26 +0200
Subject: [PATCH] Fix CI failures: constexpr, NRVO, cppcheck, IWYU (#5891)

- json_sax_dom_error_state::is_errored() cannot be constexpr: the class
  is not a literal type (GCC 4.8, GCC -Wpedantic, Clang 3.5).
- to_binary_vector: destroy the vector writer before returning, as the
  output_vector_sink sets the size of the vector in its destructor.
  Without NRVO (MSVC Debug in C++14 mode), the vector was moved out
  before it was resized.
- parser::sax_parse: return false instead of result after the early exit
  (cppcheck identicalConditionAfterEarlyExit).
- json.hpp: export detail/exceptions.hpp for IWYU, so json_view.hpp can
  name exception_id without including a detail header.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---
 include/nlohmann/detail/input/json_sax.hpp |  2 +-
 include/nlohmann/detail/input/parser.hpp   |  2 +-
 include/nlohmann/json.hpp                  | 10 +++++++---
 single_include/nlohmann/json.hpp           | 14 +++++++++-----
 4 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/include/nlohmann/detail/input/json_sax.hpp b/include/nlohmann/detail/input/json_sax.hpp
index 6a56b3453..b3dc8787c 100644
--- a/include/nlohmann/detail/input/json_sax.hpp
+++ b/include/nlohmann/detail/input/json_sax.hpp
@@ -349,7 +349,7 @@ class json_sax_dom_error_state
         return false;
     }
 
-    constexpr bool is_errored() const
+    bool is_errored() const
     {
         return errored;
     }
diff --git a/include/nlohmann/detail/input/parser.hpp b/include/nlohmann/detail/input/parser.hpp
index f06488c99..50132bdde 100644
--- a/include/nlohmann/detail/input/parser.hpp
+++ b/include/nlohmann/detail/input/parser.hpp
@@ -168,7 +168,7 @@ class parser
             return finish_input(*sax, strict);
         }
 
-        return result;
+        return false;
     }
 
   private:
diff --git a/include/nlohmann/json.hpp b/include/nlohmann/json.hpp
index 228084a5a..c0111a6dd 100644
--- a/include/nlohmann/json.hpp
+++ b/include/nlohmann/json.hpp
@@ -55,7 +55,7 @@
 #include <nlohmann/detail/abi_macros.hpp> // IWYU pragma: export
 #include <nlohmann/detail/conversions/from_json.hpp> // IWYU pragma: keep
 #include <nlohmann/detail/conversions/to_json.hpp> // IWYU pragma: keep
-#include <nlohmann/detail/exceptions.hpp>
+#include <nlohmann/detail/exceptions.hpp> // IWYU pragma: export
 #include <nlohmann/detail/hash.hpp>
 #include <nlohmann/detail/input/binary_reader.hpp>
 #include <nlohmann/detail/input/input_adapters.hpp>
@@ -3144,8 +3144,12 @@ public:
     {
         std::vector<std::uint8_t> result;
         result.reserve(detail::binary_initial_capacity(j));
-        auto writer = vector_writer(result, error_handler);
-        write(writer);
+        {
+            // the sink sets the size of result when it is destroyed, which
+            // must happen before result is returned (without NRVO, it is moved)
+            auto writer = vector_writer(result, error_handler);
+            write(writer);
+        }
         return result;
     }
 
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 92468f89e..219901b85 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -8255,7 +8255,7 @@ NLOHMANN_JSON_NAMESPACE_END
 // #include <nlohmann/detail/conversions/to_json.hpp>
 // IWYU pragma: keep
 // #include <nlohmann/detail/exceptions.hpp>
-
+// IWYU pragma: export
 // #include <nlohmann/detail/hash.hpp>
 //     __ _____ _____ _____
 //  __|  |   __|     |   | |  JSON for Modern C++
@@ -15390,7 +15390,7 @@ class json_sax_dom_error_state
         return false;
     }
 
-    constexpr bool is_errored() const
+    bool is_errored() const
     {
         return errored;
     }
@@ -21024,7 +21024,7 @@ class parser
             return finish_input(*sax, strict);
         }
 
-        return result;
+        return false;
     }
 
   private:
@@ -37855,8 +37855,12 @@ public:
     {
         std::vector<std::uint8_t> result;
         result.reserve(detail::binary_initial_capacity(j));
-        auto writer = vector_writer(result, error_handler);
-        write(writer);
+        {
+            // the sink sets the size of result when it is destroyed, which
+            // must happen before result is returned (without NRVO, it is moved)
+            auto writer = vector_writer(result, error_handler);
+            write(writer);
+        }
         return result;
     }