release candidate 4.0.6 (#2464)

* fun

* progress

* completing the documentation

.github/workflows/ubuntu24-noexcept.yml

@@ -31,4 +31,4 @@ jobs:
           echo -e '#include <simdjson.h>\nint main(int argc,char**argv) {simdjson::dom::parser parser;simdjson::dom::element tweets = parser.load(argv[1]); }' > tmp.cpp && c++ -Idestination/include -Ldestination/lib -std=c++17 -Wl,-rpath,destination/lib -o linkandrun tmp.cpp -lsimdjson && ./linkandrun jsonexamples/twitter.json &&
           mkdir testfindpackage &&
           cd testfindpackage &&
-          echo -e 'cmake_minimum_required(VERSION 3.1)\nproject(simdjsontester)\nset(CMAKE_CXX_STANDARD 17)\nfind_package(simdjson REQUIRED)'> CMakeLists.txt && mkdir build && cd build && cmake -DCMAKE_INSTALL_PREFIX:PATH=../destination .. &&  cmake --build .
+          echo -e 'cmake_minimum_required(VERSION 3.14)\nproject(simdjsontester)\nset(CMAKE_CXX_STANDARD 17)\nfind_package(simdjson REQUIRED)'> CMakeLists.txt && mkdir build && cd build && cmake -DCMAKE_INSTALL_PREFIX:PATH=../destination .. &&  cmake --build .

.github/workflows/ubuntu24-nothread.yml

@@ -31,4 +31,4 @@ jobs:
           echo -e '#include <simdjson.h>\nint main(int argc,char**argv) {simdjson::dom::parser parser;simdjson::dom::element tweets = parser.load(argv[1]); }' > tmp.cpp && c++ -Idestination/include -Ldestination/lib -std=c++17 -Wl,-rpath,destination/lib -o linkandrun tmp.cpp -lsimdjson && ./linkandrun jsonexamples/twitter.json &&
           mkdir testfindpackage &&
           cd testfindpackage &&
-          echo -e 'cmake_minimum_required(VERSION 3.1)\nproject(simdjsontester)\nset(CMAKE_CXX_STANDARD 17)\nfind_package(simdjson REQUIRED)'> CMakeLists.txt && mkdir build && cd build && cmake -DCMAKE_INSTALL_PREFIX:PATH=../destination .. &&  cmake --build .
+          echo -e 'cmake_minimum_required(VERSION 3.14)\nproject(simdjsontester)\nset(CMAKE_CXX_STANDARD 17)\nfind_package(simdjson REQUIRED)'> CMakeLists.txt && mkdir build && cd build && cmake -DCMAKE_INSTALL_PREFIX:PATH=../destination .. &&  cmake --build .

CMakeLists.txt

@@ -3,7 +3,7 @@ cmake_minimum_required(VERSION 3.14)
 project(
     simdjson
     # The version number is modified by tools/release.py
-    VERSION 4.0.2
+    VERSION 4.0.6
     DESCRIPTION "Parsing gigabytes of JSON per second"
     HOMEPAGE_URL "https://simdjson.org/"
     LANGUAGES CXX C

Doxyfile

@@ -38,7 +38,7 @@ PROJECT_NAME           = simdjson
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = "4.0.2"
+PROJECT_NUMBER         = "4.0.6"
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a

README.md

@@ -62,6 +62,7 @@ Real-world usage
 - [WasmEdge](https://wasmedge.org)
 - [RonDB](https://github.com/logicalclocks/rondb)
 - [GreptimeDB](https://github.com/GreptimeTeam/greptimedb)
+- [mamba](https://github.com/mamba-org/mamba)
 
 
 If you are planning to use simdjson in a product, please work from one of our releases.
@@ -117,9 +118,9 @@ Godbolt
 -------------
 
 Some users may want to browse code along with the compiled assembly. You want to check out the following lists of examples:
+* [C++26 reflection example](https://godbolt.org/z/K3Px64TqK)
 * [simdjson examples with errors handled through exceptions](https://godbolt.org/z/7G5qE4sr9)
 * [simdjson examples with errors without exceptions](https://godbolt.org/z/e9dWb9E4v)
-* [C++26 reflection example](https://godbolt.org/z/xK5TGKdPb)
 
 Performance results
 -------------------

benchmark/static_reflect/CMakeLists.txt

@@ -6,38 +6,42 @@ CPMAddPackage(
   EXCLUDE_FROM_ALL YES
 )
 
+option(SIMDJSON_USE_RUST "Build the static_reflect benchmark" OFF)
 
-
+if(SIMDJSON_USER_RUST)
-if(NOT WIN32)
+  if(NOT WIN32)
-# We want the check whether Rust is available before trying to build a crate.
+  # We want the check whether Rust is available before trying to build a crate.
-CPMAddPackage(
+  CPMAddPackage(
-  NAME corrosion
+    NAME corrosion
-  GITHUB_REPOSITORY corrosion-rs/corrosion
+    GITHUB_REPOSITORY corrosion-rs/corrosion
-  VERSION 0.4.4
+    VERSION 0.4.4
-  DOWNLOAD_ONLY ON
+    DOWNLOAD_ONLY ON
-  OPTIONS "Rust_FIND_QUIETLY OFF"
+    OPTIONS "Rust_FIND_QUIETLY OFF"
-)
+  )
-include("${corrosion_SOURCE_DIR}/cmake/FindRust.cmake")
+  include("${corrosion_SOURCE_DIR}/cmake/FindRust.cmake")
-endif()
-
-if(RUST_FOUND)
-  message(STATUS "Rust found: " ${Rust_VERSION} )
-  add_subdirectory("${corrosion_SOURCE_DIR}" "${PROJECT_BINARY_DIR}/_deps/corrosion" EXCLUDE_FROM_ALL)
-  # Important: we want to build in release mode!
-  corrosion_import_crate(MANIFEST_PATH "serde-benchmark/Cargo.toml" NO_LINKER_OVERRIDE PROFILE release)
-else()
-  message(STATUS "Rust/Cargo is unavailable." )
-  message(STATUS "We will not benchmark serde-benchmark." )
-  if (${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
-    message(STATUS "Under macOS, you may be able to install rust with")
-    message(STATUS "curl https://sh.rustup.rs -sSf | sh")
-  elseif(CMAKE_SYSTEM_NAME STREQUAL "Linux")
-    message(STATUS "Under Linux, you may be able to install rust with a command such as")
-    message(STATUS "apt-get install cargo" )
-    message(STATUS "or" )
-    message(STATUS "curl https://sh.rustup.rs -sSf | sh")
   endif()
-endif()
+
+  if(RUST_FOUND)
+    message(STATUS "Rust found: " ${Rust_VERSION} )
+    add_subdirectory("${corrosion_SOURCE_DIR}" "${PROJECT_BINARY_DIR}/_deps/corrosion" EXCLUDE_FROM_ALL)
+    # Important: we want to build in release mode!
+    corrosion_import_crate(MANIFEST_PATH "serde-benchmark/Cargo.toml" NO_LINKER_OVERRIDE PROFILE release)
+  else()
+    message(STATUS "Rust/Cargo is unavailable." )
+    message(STATUS "We will not benchmark serde-benchmark." )
+    if (${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
+      message(STATUS "Under macOS, you may be able to install rust with")
+      message(STATUS "curl https://sh.rustup.rs -sSf | sh")
+    elseif(CMAKE_SYSTEM_NAME STREQUAL "Linux")
+      message(STATUS "Under Linux, you may be able to install rust with a command such as")
+      message(STATUS "apt-get install cargo" )
+      message(STATUS "or" )
+      message(STATUS "curl https://sh.rustup.rs -sSf | sh")
+    endif()
+  endif()
+else(SIMDJSON_USER_RUST)
+  message(STATUS "We will not benchmark serde-benchmark." )
+endif(SIMDJSON_USER_RUST)
 
 # Add the benchmark executable targets
 add_subdirectory(twitter_benchmark)

cmake/developer-options.cmake

@@ -174,6 +174,10 @@ else()
       -Werror -Wall -Wextra -Weffc++ -Wsign-compare -Wshadow -Wwrite-strings
       -Wpointer-arith -Winit-self -Wconversion -Wno-sign-conversion
   )
+  if(CMAKE_CXX_STANDARD VERSION_GREATER_EQUAL 20)
+    target_compile_options(simdjson-internal-flags INTERFACE -Wctad-maybe-unsupported)
+  endif()
+
 endif()
 
 option(SIMDJSON_GLIBCXX_ASSERTIONS "Set _GLIBCXX_ASSERTIONS" OFF)

doc/basics.md

@@ -1395,11 +1395,14 @@ Car c = doc.get<Car>();
 
 We try to automate the parsing of any given structure or class
 by looking at its non-static public members. At compile-time,
-the library looks at a simple structre like `Car` and
+the library looks at a simple structure like `Car` and
 maps it to parsing code. We call the default constructor,
 and then assign values to the public members.
 
 
+If a key is missing in the JSON document, an error is generated (`NO_SUCH_FIELD`),
+except if the attribute is of a type like `std::optional` (`simdjson::concepts::optional_type`).
+
 #### Special cases
 
 However, there are instances where the construction cannot
@@ -1450,7 +1453,7 @@ struct complicated_weather_data {
 };
 ```
 
-The code might as simple as the following.
+The code might be as simple as the following.
 
 ```cpp
 auto padded = R"({"time":["2023-03-15T12:00:00Z"],"temperature":[42]})"_padded;
@@ -1477,6 +1480,12 @@ type without a document instance like so:
 Car car = simdjson::from(json);
 ```
 
+You can also use the `simdjson::from` syntax without exceptions, like so:
+```cpp
+Car car;
+simdjson::error_code err = simdjson::from(json_car).get(car);
+```
+
 You can also use the `simdjson::from` syntax to iterate over an array.
 
 ```cpp

doc/builder.md

@@ -34,14 +34,15 @@ It has the following methods to add content to the string:
 - `append_null()`: Appends the string "null" to the JSON buffer.
 - `clear()`: Clears the contents of the JSON buffer, resetting the position to 0 while retaining the allocated capacity.
 - `escape_and_append(std::string_view input)`: Appends a string view to the JSON buffer after escaping special characters (e.g., quotes, backslashes) as required by JSON.
-- `escape_and_append_with_quotes(std::string_view input)` Appends a string view surrounded by double quotes (e.g., "input") to the JSON buffer after escaping special characters.
+- `escape_and_append_with_quotes(std::string_view input)` Appends a string view surrounded by double quotes (e.g., "input") to the JSON buffer after escaping special characters. For constant strings, you may also do `escape_and_append_with_quotes<"mystring">()`.
-Parameters:
 - `escape_and_append_with_quotes(char input)`: Appends a single character surrounded by double quotes (e.g., "c") to the JSON buffer after escaping it if necessary.
 - `append_raw(const char *c)`: Appends a null-terminated C string directly to the JSON buffer without escaping.
 - `append_raw(std::string_view input)`: Appends a string view directly to the JSON buffer without escaping.
 - `append_raw(const char *str, size_t len)`: Appends a specified number of characters from a C string directly to the JSON
+- `append_key_value(key,value)`: Appends a key and a value (`"json":somevalue`)
+- `append_key_value<"mykey">(value)`: Appends a key and a value (`"json":somevalue`), useful when the key is a compile-time constant (C++20).
 
-After writting the content, if you have reasons to believe that the content might violate UTF-8 conventions, you can check it as follows:
+After writing the content, if you have reasons to believe that the content might violate UTF-8 conventions, you can check it as follows:
 
 - `validate_unicode()`: Checks if the content in the JSON buffer is valid UTF-8. Returns: true if the content is valid UTF-8, false otherwise.
 
@@ -52,7 +53,7 @@ Once you are satisfied, you can recover the string as follows:
 
 - `operator std::string()`: Converts the JSON buffer to an std::string. (Might throw if an error occurred.)
 - `operator std::string_view()`: Converts the JSON buffer to an std::string_view.  (Might throw if an error occurred.)
-- `view()`: Returns a view of the written JSON buffer as a `simdjson_result<std::string_view>`.
+- `view()`: Returns a view of the written JSON buffer as a `simdjson_result<std::string_view>` (C++20).
 
 The later method (`view()`) is recommended.  For performance reasons, we expect you to explicitly call `validate_unicode()` as needed (e.g., prior to calling `view()`).
 
@@ -131,20 +132,20 @@ In all cases, the `std::string_view` instance depends the corresponding `string_
 
 
 
-If you have C++20, you can simplify the code, as the `std::vector<double>` is automatically
+If you have C++20, you can simplify the code, as the `std::vector<double>` is automatically supported. Further, we can pass the keys (which are compile-time
-supported.
+constant) as template parameter (for improved performance).
 
 ```cpp
     Car c = {"Toyota", "Corolla", 2017, {30.0,30.2,30.513,30.79}};
     simdjson::builder::string_builder sb;
     sb.start_object();
-    sb.append_key_value("make", c.make);
+    sb.append_key_value<"make">(c.make);
     sb.append_comma();
-    sb.append_key_value("model", c.model);
+    sb.append_key_value<"model">(c.model);
     sb.append_comma();
-    sb.append_key_value("year", c.year);
+    sb.append_key_value<"year">(c.year);
     sb.append_comma();
-    sb.append_key_value("tire_pressure", c.tire_pressure);
+    sb.append_key_value<"tire_pressure">(c.tire_pressure);
     sb.end_object();
     std::string_view p = sb.view();
 ```
@@ -175,9 +176,52 @@ std::vector<std::vector<double>> c = {{1.0, 2.0}, {3.0, 4.0}};
 std::string json = simdjson::to_json(c);
 ```
 
+We also have an overload for when you want to reuse the same `std::string` instance:
+
+
+```cpp
+std::vector<std::vector<double>> c = {{1.0, 2.0}, {3.0, 4.0}};
+std::string json;
+auto error = simdjson::to_json(c, json);
+if(error) { /* there was an error */ }
+```
+
+
 We do recommend that you create and reuse the `string_builder` instance for performance
 reasons.
 
+You can also add custom serialization functions using a `tag_invoke` function.
+For example, the following
+function will allow you to serialize instances of the type `Car`.
+
+```cpp
+#include <simdjson>
+
+struct Car {
+  std::string make;
+  std::string model;
+  int64_t year;
+  std::vector<float> tire_pressure;
+};
+
+namespace simdjson {
+
+template <typename builder_type>
+void tag_invoke(serialize_tag, builder_type &builder, const Car& car) {
+  builder.start_object();
+  builder.append_key_value("make", car.make);
+  builder.append_comma();
+  builder.append_key_value("model", car.model);
+  builder.append_comma();
+  builder.append_key_value("year", car.year);
+  builder.append_comma();
+  builder.append_key_value("tire_pressure", car.tire_pressure);
+  builder.end_object();
+}
+
+} // namespace simdjson
+```
+
 C++26 static reflection
 ------------------------
 
@@ -239,7 +283,17 @@ with the `simdjson::to_json` template function.
 If you know the output size, in bytes, of your JSON string, you may
 pass it as a second parameter (e.g., `simdjson::to_json(c, 31123)`).
 
+Sometimes you may want to reuse the same `std::string` instance. We
+have an overload for this purpose:
 
+```cpp
+Car c = {"Toyota", "Corolla", 2017, {30.0,30.2,30.513,30.79}};
+std::string s;
+auto error = simdjson::to_json(c, s);
+if(error) { /* there was an error */ }
+```
+
+You can then also add a third parameter for the expected output size in bytes.
 
 ### Without `string_buffer` instance but with explicit error handling
 
@@ -248,9 +302,44 @@ pattern:
 
 ```cpp
   std::string json;
-  if(simdjson::to(c).get(json)) {
+  if(simdjson::to_json(c).get(json)) {
     // there was an error
   } else {
     // json contain the serialized JSON
   }
 ```
+
+### Customization
+
+If you want to serialize a value in a custome way, you can do it with a
+`tag_invoke` specialization like the following example which will map
+the year attribute to a string.
+
+
+```cpp
+#include <simdjson>
+
+struct Car {
+  std::string make;
+  std::string model;
+  int64_t year;
+  std::vector<float> tire_pressure;
+};
+
+namespace simdjson {
+
+template <typename builder_type>
+void tag_invoke(serialize_tag, builder_type &builder, const Car& car) {
+  builder.start_object();
+  builder.append_key_value("make", car.make);
+  builder.append_comma();
+  builder.append_key_value("model", car.model);
+  builder.append_comma();
+  builder.append_key_value("year", std::to_string(car.year));
+  builder.append_comma();
+  builder.append_key_value("tire_pressure", car.tire_pressure);
+  builder.end_object();
+}
+
+} // namespace simdjson
+```

doc/dom.md

@@ -129,7 +129,7 @@ Once you have an element, you can navigate it with idiomatic C++ iterators, oper
   The strings contain unescaped valid UTF-8 strings: no unmatched surrogate is allowed.
   Internally, numbers are stored as either 64-bit integers or 64-bit floating-point numbers.
   Thus it is possible to get the full 64-bit integer range (either signed or  unsigned).
-  By default, the string `-0` is parsed as the integer 0 as in Pytho or C++. If you set the macro
+  By default, the string `-0` is parsed as the integer 0 as in Python or C++. If you set the macro
   `SIMDJSON_MINUS_ZERO_AS_FLOAT` to `1` when building simdjson, you can get that `-0` is mapped to `-0.0`
   as in JavaScript. You can get the desired effect by building simdjson with cmake setting the
   `SIMDJSON_MINUS_ZERO_AS_FLOAT` to on: `cmake -B build -D SIMDJSON_MINUS_ZERO_AS_FLOAT=ON`.

include/simdjson/concepts.h

@@ -122,11 +122,32 @@ concept optional_type = requires(std::remove_cvref_t<T> obj) {
     } -> std::convertible_to<typename std::remove_cvref_t<T>::value_type>;
   };
   { static_cast<bool>(obj) } -> std::same_as<bool>; // convertible to bool
+  { obj.reset() } noexcept -> std::same_as<void>;
 };
 
 
 
+
+
 } // namespace concepts
+
+
+/**
+ * We use tag_invoke as our customization point mechanism.
+ */
+template <typename Tag, typename... Args>
+concept tag_invocable = requires(Tag tag, Args... args) {
+  tag_invoke(std::forward<Tag>(tag), std::forward<Args>(args)...);
+};
+
+template <typename Tag, typename... Args>
+concept nothrow_tag_invocable =
+    tag_invocable<Tag, Args...> && requires(Tag tag, Args... args) {
+      {
+        tag_invoke(std::forward<Tag>(tag), std::forward<Args>(args)...)
+      } noexcept;
+    };
+
 } // namespace simdjson
 #endif // SIMDJSON_SUPPORTS_CONCEPTS
 #endif // SIMDJSON_CONCEPTS_H

include/simdjson/convert-inl.h

@@ -58,6 +58,12 @@ inline simdjson_result<T> auto_parser<parser_type>::result() noexcept(is_nothrow
   return m_doc.get<T>();
 }
 
+template <typename parser_type>
+template <typename T>
+simdjson_warn_unused simdjson_inline error_code auto_parser<parser_type>::get(T &value) && noexcept(is_nothrow_gettable<T>) {
+  return result<T>().get(value);
+}
+
 template <typename parser_type>
 inline simdjson_result<ondemand::array> auto_parser<parser_type>::array() noexcept {
   return result<ondemand::array>();
@@ -73,12 +79,7 @@ inline simdjson_result<ondemand::number> auto_parser<parser_type>::number() noex
   return result<ondemand::number>();
 }
 
-template <typename parser_type>
+#if SIMDJSON_EXCEPTIONS
-template <typename T>
-inline auto_parser<parser_type>::operator simdjson_result<T>() noexcept(is_nothrow_gettable<T>) {
-  return result<T>();
-}
-
 template <typename parser_type>
 template <typename T>
 inline auto_parser<parser_type>::operator T() noexcept(false) {
@@ -87,6 +88,7 @@ inline auto_parser<parser_type>::operator T() noexcept(false) {
   }
   return m_doc.get<T>();
 }
+#endif // SIMDJSON_EXCEPTIONS
 
 template <typename parser_type>
 template <typename T>
@@ -109,13 +111,23 @@ inline T to_adaptor<T>::operator()(simdjson_result<ondemand::value> &val) const
 
 template <typename T>
 inline auto to_adaptor<T>::operator()(padded_string_view const str) const noexcept {
-  return auto_parser{str};
+  return auto_parser<ondemand::parser *>{str};
 }
 
 template <typename T>
 inline auto to_adaptor<T>::operator()(ondemand::parser &parser, padded_string_view const str) const noexcept {
   return auto_parser<ondemand::parser *>{parser, str};
 }
+
+template <typename T>
+inline auto to_adaptor<T>::operator()(std::string str) const noexcept {
+  return auto_parser<ondemand::parser *>{pad_with_reserve(str)};
+}
+
+template <typename T>
+inline auto to_adaptor<T>::operator()(ondemand::parser &parser, std::string str) const noexcept {
+  return auto_parser<ondemand::parser *>{parser, pad_with_reserve(str)};
+}
 } // namespace internal
 } // namespace convert
 } // namespace simdjson

include/simdjson/convert.h

@@ -46,16 +46,19 @@ public:
 
 	template <typename T>
 	simdjson_warn_unused simdjson_inline simdjson_result<T> result() noexcept(is_nothrow_gettable<T>);
+	template <typename T>
+	simdjson_warn_unused simdjson_inline error_code get(T &value) && noexcept(is_nothrow_gettable<T>);
+
 
 	simdjson_warn_unused simdjson_inline simdjson_result<ondemand::array> array() noexcept;
 	simdjson_warn_unused simdjson_inline simdjson_result<ondemand::object> object() noexcept;
 	simdjson_warn_unused simdjson_inline simdjson_result<ondemand::number> number() noexcept;
 
-	template <typename T>
-	simdjson_warn_unused simdjson_inline explicit(false) operator simdjson_result<T>() noexcept(is_nothrow_gettable<T>);
 
+#if SIMDJSON_EXCEPTIONS
 	template <typename T>
 	simdjson_warn_unused simdjson_inline explicit(false) operator T() noexcept(false);
+#endif // SIMDJSON_EXCEPTIONS
 
 	template <typename T>
 	simdjson_warn_unused simdjson_inline std::optional<T> optional() noexcept(is_nothrow_gettable<T>);
@@ -72,7 +75,14 @@ struct to_adaptor {
 	T operator()(simdjson_result<ondemand::value> &val) const noexcept;
 	auto operator()(padded_string_view const str) const noexcept;
 	auto operator()(ondemand::parser &parser, padded_string_view const str) const noexcept;
+	// The std::string is padded with reserve to ensure there is enough space for padding.
+	// Some sanitizers may not like this, so you can use simdjson::pad instead.
+	// simdjson::from(simdjson::pad(str))
+	auto operator()(std::string str) const noexcept;
+	auto operator()(ondemand::parser &parser, std::string str) const noexcept;
 };
+// deduction guide
+auto_parser(padded_string_view const str) -> auto_parser<ondemand::parser*>;
 } // namespace internal
 } // namespace convert
 

include/simdjson/generic/ondemand/deserialize.h

@@ -7,55 +7,8 @@
 #include "simdjson/generic/ondemand/array.h"
 #endif // SIMDJSON_CONDITIONAL_INCLUDE
 
-#include <concepts>
 namespace simdjson {
 
-namespace tag_invoke_fn_ns {
-void tag_invoke();
-
-struct tag_invoke_fn {
-  template <typename Tag, typename... Args>
-    requires requires(Tag tag, Args &&...args) {
-      tag_invoke(std::forward<Tag>(tag), std::forward<Args>(args)...);
-    }
-  constexpr auto operator()(Tag tag, Args &&...args) const
-      noexcept(noexcept(tag_invoke(std::forward<Tag>(tag),
-                                   std::forward<Args>(args)...)))
-          -> decltype(tag_invoke(std::forward<Tag>(tag),
-                                 std::forward<Args>(args)...)) {
-    return tag_invoke(std::forward<Tag>(tag), std::forward<Args>(args)...);
-  }
-};
-} // namespace tag_invoke_fn_ns
-
-inline namespace tag_invoke_ns {
-inline constexpr tag_invoke_fn_ns::tag_invoke_fn tag_invoke = {};
-} // namespace tag_invoke_ns
-
-template <typename Tag, typename... Args>
-concept tag_invocable = requires(Tag tag, Args... args) {
-  tag_invoke(std::forward<Tag>(tag), std::forward<Args>(args)...);
-};
-
-template <typename Tag, typename... Args>
-concept nothrow_tag_invocable =
-    tag_invocable<Tag, Args...> && requires(Tag tag, Args... args) {
-      {
-        tag_invoke(std::forward<Tag>(tag), std::forward<Args>(args)...)
-      } noexcept;
-    };
-
-template <typename Tag, typename... Args>
-using tag_invoke_result =
-    std::invoke_result<decltype(tag_invoke), Tag, Args...>;
-
-template <typename Tag, typename... Args>
-using tag_invoke_result_t =
-    std::invoke_result_t<decltype(tag_invoke), Tag, Args...>;
-
-template <auto &Tag> using tag_t = std::decay_t<decltype(Tag)>;
-
-
 struct deserialize_tag;
 
 /// These types are deserializable in a built-in way

include/simdjson/generic/ondemand/json_builder.h

@@ -38,7 +38,7 @@ concept container_but_not_string =
     !std::is_same_v<T, std::string_view> && !std::is_same_v<T, const char *>;
 
 template <class T>
-  requires(container_but_not_string<T>)
+  requires(container_but_not_string<T> && !require_custom_serialization<T>)
 constexpr void atom(string_builder &b, const T &t) {
   if (t.size() == 0) {
     b.append_raw("[]");
@@ -63,6 +63,7 @@ constexpr void atom(string_builder &b, const T &t) {
 }
 
 template <concepts::string_view_keyed_map T>
+  requires(!require_custom_serialization<T>)
 constexpr void atom(string_builder &b, const T &m) {
   if (m.empty()) {
     b.append_raw("{}");
@@ -99,7 +100,7 @@ template <class T>
            !std::is_same_v<T, std::string> &&
            !std::is_same_v<T, std::string_view> &&
            !std::is_same_v<T, const char*> &&
-           !std::is_same_v<T, char>)
+           !std::is_same_v<T, char> && !require_custom_serialization<T>)
 constexpr void atom(string_builder &b, const T &t) {
   int i = 0;
   b.append('{');
@@ -117,6 +118,7 @@ constexpr void atom(string_builder &b, const T &t) {
 
 // Support for optional types (std::optional, etc.)
 template <concepts::optional_type T>
+  requires(!require_custom_serialization<T>)
 constexpr void atom(string_builder &b, const T &opt) {
   if (opt) {
     atom(b, opt.value());
@@ -127,6 +129,7 @@ constexpr void atom(string_builder &b, const T &opt) {
 
 // Support for smart pointers (std::unique_ptr, std::shared_ptr, etc.)
 template <concepts::smart_pointer T>
+  requires(!require_custom_serialization<T>)
 constexpr void atom(string_builder &b, const T &ptr) {
   if (ptr) {
     atom(b, *ptr);
@@ -137,7 +140,7 @@ constexpr void atom(string_builder &b, const T &ptr) {
 
 // Support for enums - serialize as string representation using expand approach from P2996R12
 template <typename T>
-  requires(std::is_enum_v<T>)
+  requires(std::is_enum_v<T> && !require_custom_serialization<T>)
 void atom(string_builder &b, const T &e) {
 #if SIMDJSON_STATIC_REFLECTION
   constexpr auto enumerators = std::define_static_array(std::meta::enumerators_of(^^T));
@@ -161,7 +164,7 @@ template <concepts::appendable_containers T>
   requires(!container_but_not_string<T> && !concepts::string_view_keyed_map<T> &&
            !concepts::optional_type<T> && !concepts::smart_pointer<T> &&
            !std::is_same_v<T, std::string> &&
-           !std::is_same_v<T, std::string_view> && !std::is_same_v<T, const char*>)
+           !std::is_same_v<T, std::string_view> && !std::is_same_v<T, const char*> && !require_custom_serialization<T>)
 constexpr void atom(string_builder &b, const T &container) {
   if (container.empty()) {
     b.append_raw("[]");
@@ -196,11 +199,13 @@ void append(string_builder &b, const T &t) {
 }
 
 template <concepts::optional_type T>
+  requires(!require_custom_serialization<T>)
 void append(string_builder &b, const T &t) {
   atom(b, t);
 }
 
 template <concepts::smart_pointer T>
+  requires(!require_custom_serialization<T>)
 void append(string_builder &b, const T &t) {
   atom(b, t);
 }
@@ -209,12 +214,13 @@ template <concepts::appendable_containers T>
   requires(!container_but_not_string<T> && !concepts::string_view_keyed_map<T> &&
            !concepts::optional_type<T> && !concepts::smart_pointer<T> &&
            !std::is_same_v<T, std::string> &&
-           !std::is_same_v<T, std::string_view> && !std::is_same_v<T, const char*>)
+           !std::is_same_v<T, std::string_view> && !std::is_same_v<T, const char*> && !require_custom_serialization<T>)
 void append(string_builder &b, const T &t) {
   atom(b, t);
 }
 
 template <concepts::string_view_keyed_map T>
+  requires(!require_custom_serialization<T>)
 void append(string_builder &b, const T &t) {
   atom(b, t);
 }
@@ -229,7 +235,7 @@ template <class Z>
            !std::is_same_v<Z, std::string> &&
            !std::is_same_v<Z, std::string_view> &&
            !std::is_same_v<Z, const char*> &&
-           !std::is_same_v<Z, char>)
+           !std::is_same_v<Z, char> && !require_custom_serialization<Z>)
 void append(string_builder &b, const Z &z) {
   int i = 0;
   b.append('{');
@@ -247,7 +253,7 @@ void append(string_builder &b, const Z &z) {
 
 // works for container
 template <class Z>
-  requires(container_but_not_string<Z>)
+  requires(container_but_not_string<Z> && !require_custom_serialization<Z>)
 void append(string_builder &b, const Z &z) {
   if (z.size() == 0) {
     b.append_raw("[]");
@@ -263,7 +269,14 @@ void append(string_builder &b, const Z &z) {
 }
 
 template <class Z>
-simdjson_result<std::string> to_json_string(const Z &z, size_t initial_capacity = 1024) {
+  requires (require_custom_serialization<Z>)
+void append(string_builder &b, const Z &z) {
+  b.append(z);
+}
+
+
+template <class Z>
+simdjson_warn_unused simdjson_result<std::string> to_json_string(const Z &z, size_t initial_capacity = string_builder::DEFAULT_INITIAL_CAPACITY) {
   string_builder b(initial_capacity);
   append(b, z);
   std::string_view s;
@@ -272,8 +285,8 @@ simdjson_result<std::string> to_json_string(const Z &z, size_t initial_capacity
 }
 
 template <class Z>
-simdjson_error to_json(const Z &z, std::string &s) {
+simdjson_warn_unused simdjson_error to_json(const Z &z, std::string &s, size_t initial_capacity = string_builder::DEFAULT_INITIAL_CAPACITY) {
-  string_builder b;
+  string_builder b(initial_capacity);
   append(b, z);
   std::string_view view;
   if(auto e = b.view().get(view); e) { return e; }
@@ -290,9 +303,13 @@ string_builder& operator<<(string_builder& b, const Z& z) {
 } // namespace SIMDJSON_IMPLEMENTATION
 // Alias the function template to 'to' in the global namespace
 template <class Z>
-simdjson_result<std::string> to_json(const Z &z, size_t initial_capacity = 1024) {
+simdjson_warn_unused simdjson_result<std::string> to_json(const Z &z, size_t initial_capacity = SIMDJSON_IMPLEMENTATION::builder::string_builder::DEFAULT_INITIAL_CAPACITY) {
   return SIMDJSON_IMPLEMENTATION::builder::to_json_string(z, initial_capacity);
 }
+template <class Z>
+simdjson_warn_unused simdjson_error to_json(const Z &z, std::string &s, size_t initial_capacity = SIMDJSON_IMPLEMENTATION::builder::string_builder::DEFAULT_INITIAL_CAPACITY) {
+  return SIMDJSON_IMPLEMENTATION::builder::to_json(z, s, initial_capacity);
+}
 } // namespace simdjson
 
 #endif // SIMDJSON_STATIC_REFLECTION

include/simdjson/generic/ondemand/json_string_builder-inl.h

@@ -284,10 +284,12 @@ simdjson_inline void string_builder::clear() noexcept {
 
 namespace internal {
 
-// We could specialize further for 32-bit integers.
-simdjson_really_inline int int_log2(uint32_t x) { return (63 - leading_zeroes(x | 1)); }
 
-simdjson_really_inline int fast_digit_count(uint32_t x) {
+template <typename number_type, typename = typename std::enable_if<
+                                    std::is_unsigned<number_type>::value>::type>
+simdjson_really_inline int int_log2(number_type x) { return 63 - leading_zeroes(uint64_t(x) | 1); }
+
+simdjson_really_inline int fast_digit_count_32(uint32_t x) {
   static uint64_t table[] = {
       4294967296,  8589934582,  8589934582,  8589934582,  12884901788,
       12884901788, 12884901788, 17179868184, 17179868184, 17179868184,
@@ -299,9 +301,8 @@ simdjson_really_inline int fast_digit_count(uint32_t x) {
   return uint32_t((x + table[int_log2(x)]) >> 32);
 }
 
-simdjson_really_inline int int_log2(uint64_t x) { return 63 - leading_zeroes(x | 1); }
 
-simdjson_really_inline int fast_digit_count(uint64_t x) {
+simdjson_really_inline int fast_digit_count_64(uint64_t x) {
   static uint64_t table[] = {9,
                              99,
                              999,
@@ -332,7 +333,11 @@ simdjson_really_inline size_t digit_count(number_type v) noexcept {
   static_assert(sizeof(number_type) == 8 || sizeof(number_type) == 4 ||
                     sizeof(number_type) == 2 || sizeof(number_type) == 1,
                 "We only support 8-bit, 16-bit, 32-bit and 64-bit numbers");
-  return fast_digit_count(v);
+  SIMDJSON_IF_CONSTEXPR(sizeof(number_type) <= 4) {
+    return fast_digit_count_32(static_cast<uint32_t>(v));
+  } else {
+    return fast_digit_count_64(static_cast<uint64_t>(v));
+  }
 }
 static const char decimal_table[200] = {
   0x30, 0x30, 0x30, 0x31, 0x30, 0x32, 0x30, 0x33, 0x30, 0x34, 0x30, 0x35,
@@ -355,6 +360,7 @@ static const char decimal_table[200] = {
 };
 } // namespace internal
 
+
 template <typename number_type, typename>
 simdjson_inline void string_builder::append(number_type v) noexcept {
   static_assert(std::is_same<number_type, bool>::value ||
@@ -470,6 +476,12 @@ simdjson_inline void string_builder::escape_and_append_with_quotes(const char* i
   std::string_view cinput(input);
   escape_and_append_with_quotes(cinput);
 }
+#if SIMDJSON_SUPPORTS_CONCEPTS
+template<internal::fixed_string key>
+simdjson_inline void string_builder::escape_and_append_with_quotes()  noexcept {
+  escape_and_append_with_quotes(internal::string_constant<key>::value);
+}
+#endif
 
 simdjson_inline void string_builder::append_raw(const char *c) noexcept {
   size_t len = std::strlen(c);
@@ -494,6 +506,7 @@ simdjson_inline void string_builder::append_raw(const char *str,
 #if SIMDJSON_SUPPORTS_CONCEPTS
 // Support for optional types (std::optional, etc.)
 template <concepts::optional_type T>
+ requires(!require_custom_serialization<T>)
 simdjson_inline void string_builder::append(const T &opt) {
   if (opt) {
     append(*opt);
@@ -501,9 +514,17 @@ simdjson_inline void string_builder::append(const T &opt) {
     append_null();
   }
 }
+
+
+template <typename T>
+requires(require_custom_serialization<T>)
+simdjson_inline void string_builder::append(const T &val) {
+  serialize(*this, val);
+}
+
 template <typename T>
 requires(std::is_convertible<T, std::string_view>::value ||
-std::is_same<T, const char*>::value )
+std::is_same<T, const char*>::value)
 simdjson_inline void string_builder::append(const T &value) {
   escape_and_append_with_quotes(value);
 }
@@ -649,6 +670,25 @@ simdjson_inline void string_builder::append_key_value(key_type key, value_type v
   }
 }
 
+#if SIMDJSON_SUPPORTS_CONCEPTS
+template<internal::fixed_string key, typename value_type>
+simdjson_inline void string_builder::append_key_value(value_type value) noexcept {
+  escape_and_append_with_quotes<key>();
+  append_colon();
+  SIMDJSON_IF_CONSTEXPR(std::is_same<value_type, std::nullptr_t>::value) {
+    append_null();
+  } else SIMDJSON_IF_CONSTEXPR(std::is_same<value_type, char>::value) {
+    escape_and_append_with_quotes(value);
+  } else SIMDJSON_IF_CONSTEXPR(std::is_convertible<value_type, std::string_view>::value) {
+    escape_and_append_with_quotes(value);
+  } else SIMDJSON_IF_CONSTEXPR(std::is_same<value_type, const char*>::value) {
+    escape_and_append_with_quotes(value);
+  } else {
+    append(value);
+  }
+}
+#endif
+
 } // namespace builder
 } // namespace SIMDJSON_IMPLEMENTATION
 } // namespace simdjson

include/simdjson/generic/ondemand/json_string_builder.h

@@ -10,9 +10,62 @@
 #endif // SIMDJSON_CONDITIONAL_INCLUDE
 
 namespace simdjson {
+
+
+#if SIMDJSON_SUPPORTS_CONCEPTS
+
 namespace SIMDJSON_IMPLEMENTATION {
 namespace builder {
+  class string_builder;
+}}
 
+template <typename T, typename = void>
+struct has_custom_serialization : std::false_type {};
+
+inline constexpr struct serialize_tag {
+  template <typename T>
+    requires custom_deserializable<T>
+  constexpr void operator()(SIMDJSON_IMPLEMENTATION::builder::string_builder& b, T& obj) const{
+    return tag_invoke(*this, b, obj);
+  }
+
+
+} serialize{};
+template <typename T>
+struct has_custom_serialization<T, std::void_t<
+    decltype(tag_invoke(serialize, std::declval<SIMDJSON_IMPLEMENTATION::builder::string_builder&>(), std::declval<T&>()))
+>> : std::true_type {};
+
+template <typename T>
+constexpr bool require_custom_serialization = has_custom_serialization<T>::value;
+#else
+struct has_custom_serialization : std::false_type {};
+#endif // SIMDJSON_SUPPORTS_CONCEPTS
+
+namespace SIMDJSON_IMPLEMENTATION {
+namespace builder {
+#if SIMDJSON_SUPPORTS_CONCEPTS
+// Helper to create string constants
+namespace internal {
+template <std::size_t N>
+struct fixed_string {
+    constexpr fixed_string(const char (&str)[N])  {
+        for (std::size_t i = 0; i < N; ++i) {
+            data[i] = str[i];
+        }
+    }
+    char data[N];
+    constexpr std::string_view view() const { return {data, N - 1}; }
+};
+template <std::size_t N>
+fixed_string(const char (&)[N]) -> fixed_string<N>;
+
+template <fixed_string str>
+struct string_constant {
+    static constexpr std::string_view value = str.view();
+};
+} // namespace internal
+#endif // SIMDJSON_SUPPORTS_CONCEPTS
 /**
  * A builder for JSON strings representing documents. This is a low-level
  * builder that is not meant to be used directly by end-users. Though it
@@ -24,7 +77,9 @@ namespace builder {
  */
 class string_builder {
 public:
-  simdjson_inline string_builder(size_t initial_capacity = 1024);
+  simdjson_inline string_builder(size_t initial_capacity = DEFAULT_INITIAL_CAPACITY);
+
+  static constexpr size_t DEFAULT_INITIAL_CAPACITY = 1024;
 
   /**
    * Append number (includes Booleans). Booleans are mapped to the strings
@@ -33,7 +88,7 @@ public:
    * represents the number.
    */
   template<typename number_type,
-         typename = typename std::enable_if<std::is_arithmetic<number_type>::value>::type>
+    typename = typename std::enable_if<std::is_arithmetic<number_type>::value>::type>
   simdjson_inline void append(number_type v) noexcept;
 
   /**
@@ -62,7 +117,10 @@ public:
    * There is no UTF-8 validation.
    */
   simdjson_inline void escape_and_append_with_quotes(std::string_view input)  noexcept;
-
+#if SIMDJSON_SUPPORTS_CONCEPTS
+  template<internal::fixed_string key>
+  simdjson_inline void escape_and_append_with_quotes()  noexcept;
+#endif
   /**
    * Append the character surrounded by double quotes, after escaping it.
    * There is no UTF-8 validation.
@@ -116,13 +174,21 @@ public:
    * The key is escaped and surrounded by double quotes.
    * The value is escaped if it is a string.
    */
-   template<typename key_type, typename value_type>
+  template<typename key_type, typename value_type>
   simdjson_inline void append_key_value(key_type key, value_type value) noexcept;
 #if SIMDJSON_SUPPORTS_CONCEPTS
+  template<internal::fixed_string key, typename value_type>
+  simdjson_inline void append_key_value(value_type value) noexcept;
+
   // Support for optional types (std::optional, etc.)
   template <concepts::optional_type T>
+  requires(!require_custom_serialization<T>)
   simdjson_inline void append(const T &opt);
 
+  template <typename T>
+  requires(require_custom_serialization<T>)
+  simdjson_inline void append(const T &val);
+
   // Support for string-like types
   template <typename T>
   requires(std::is_convertible<T, std::string_view>::value ||
@@ -232,7 +298,7 @@ private:
 #if !SIMDJSON_STATIC_REFLECTION
 // fallback implementation until we have static reflection
 template <class Z>
-simdjson_result<std::string> to_json(const Z &z, size_t initial_capacity = 1024) {
+simdjson_warn_unused simdjson_result<std::string> to_json(const Z &z, size_t initial_capacity = simdjson::SIMDJSON_IMPLEMENTATION::builder::string_builder::DEFAULT_INITIAL_CAPACITY) {
   simdjson::SIMDJSON_IMPLEMENTATION::builder::string_builder b(initial_capacity);
   b.append(z);
   std::string_view s;
@@ -240,8 +306,20 @@ simdjson_result<std::string> to_json(const Z &z, size_t initial_capacity = 1024)
   if(e) { return e; }
   return std::string(s);
 }
+template <class Z>
+simdjson_warn_unused simdjson_error to_json(const Z &z, std::string &s, size_t initial_capacity = simdjson::SIMDJSON_IMPLEMENTATION::builder::string_builder::DEFAULT_INITIAL_CAPACITY) {
+  simdjson::SIMDJSON_IMPLEMENTATION::builder::string_builder b(initial_capacity);
+  b.append(z);
+  std::string_view sv;
+  auto e = b.view().get(sv);
+  if(e) { return e; }
+  s.assign(sv.data(), sv.size());
+  return simdjson::SUCCESS;
+}
 #endif
 
+#if SIMDJSON_SUPPORTS_CONCEPTS
+#endif // SIMDJSON_SUPPORTS_CONCEPTS
 
 } // namespace simdjson
 

include/simdjson/generic/ondemand/std_deserialize.h

@@ -16,15 +16,12 @@
 #endif
 
 namespace simdjson {
-template <typename T>
-constexpr bool require_custom_serialization = false;
 
 //////////////////////////////
 // Number deserialization
 //////////////////////////////
 
 template <std::unsigned_integral T>
-  requires(!require_custom_serialization<T>)
 error_code tag_invoke(deserialize_tag, auto &val, T &out) noexcept {
   using limits = std::numeric_limits<T>;
 
@@ -38,7 +35,6 @@ error_code tag_invoke(deserialize_tag, auto &val, T &out) noexcept {
 }
 
 template <std::floating_point T>
-  requires(!require_custom_serialization<T>)
 error_code tag_invoke(deserialize_tag, auto &val, T &out) noexcept {
   double x;
   SIMDJSON_TRY(val.get_double().get(x));
@@ -47,7 +43,6 @@ error_code tag_invoke(deserialize_tag, auto &val, T &out) noexcept {
 }
 
 template <std::signed_integral T>
-  requires(!require_custom_serialization<T>)
 error_code tag_invoke(deserialize_tag, auto &val, T &out) noexcept {
   using limits = std::numeric_limits<T>;
 
@@ -77,7 +72,6 @@ error_code tag_invoke(deserialize_tag, auto &val, char &out) noexcept {
 
 // any string-like type (can be constructed from std::string_view)
 template <concepts::constructible_from_string_view T, typename ValT>
-  requires(!require_custom_serialization<T>)
 error_code tag_invoke(deserialize_tag, ValT &val, T &out) noexcept(std::is_nothrow_constructible_v<T, std::string_view>) {
   std::string_view str;
   SIMDJSON_TRY(val.get_string().get(str));
@@ -94,7 +88,6 @@ error_code tag_invoke(deserialize_tag, ValT &val, T &out) noexcept(std::is_nothr
  * doc.get<std::vector<int>>().
  */
 template <concepts::appendable_containers T, typename ValT>
-  requires(!require_custom_serialization<T>)
 error_code tag_invoke(deserialize_tag, ValT &val, T &out) noexcept(false) {
   using value_type = typename std::remove_cvref_t<T>::value_type;
   static_assert(
@@ -140,7 +133,6 @@ error_code tag_invoke(deserialize_tag, ValT &val, T &out) noexcept(false) {
  * string-keyed types.
  */
  template <concepts::string_view_keyed_map T, typename ValT>
- requires(!require_custom_serialization<T>)
 error_code tag_invoke(deserialize_tag, ValT &val, T &out) noexcept(false) {
   using value_type = typename std::remove_cvref_t<T>::mapped_type;
   static_assert(
@@ -222,7 +214,6 @@ error_code tag_invoke(deserialize_tag, SIMDJSON_IMPLEMENTATION::ondemand::docume
  * @return status of the conversion
  */
 template <concepts::smart_pointer T, typename ValT>
-  requires(!require_custom_serialization<T>)
 error_code tag_invoke(deserialize_tag, ValT &val, T &out) noexcept(nothrow_deserializable<typename std::remove_cvref_t<T>::element_type, ValT>) {
   using element_type = typename std::remove_cvref_t<T>::element_type;
 
@@ -248,7 +239,6 @@ error_code tag_invoke(deserialize_tag, ValT &val, T &out) noexcept(nothrow_deser
  * This CPO (Customization Point Object) will help deserialize into optional types.
  */
 template <concepts::optional_type T>
-  requires(!require_custom_serialization<T>)
 error_code tag_invoke(deserialize_tag, auto &val, T &out) noexcept(nothrow_deserializable<typename std::remove_cvref_t<T>::value_type, decltype(val)>) {
   using value_type = typename std::remove_cvref_t<T>::value_type;
 
@@ -274,7 +264,7 @@ error_code tag_invoke(deserialize_tag, auto &val, T &out) noexcept(nothrow_deser
 template <typename T>
 constexpr bool user_defined_type = (std::is_class_v<T>
 && !std::is_same_v<T, std::string> && !std::is_same_v<T, std::string_view> && !concepts::optional_type<T> &&
-!concepts::appendable_containers<T> && !require_custom_serialization<T>);
+!concepts::appendable_containers<T>);
 
 
 template <typename T, typename ValT>
@@ -286,18 +276,26 @@ error_code tag_invoke(deserialize_tag, ValT &val, T &out) noexcept {
   } else {
     SIMDJSON_TRY(val.get_object().get(obj));
   }
-  error_code e = simdjson::SUCCESS;
   template for (constexpr auto mem : std::define_static_array(std::meta::nonstatic_data_members_of(^^T, std::meta::access_context::unchecked()))) {
-        if constexpr (!std::meta::is_const(mem) && std::meta::is_public(mem)) {
+    if constexpr (!std::meta::is_const(mem) && std::meta::is_public(mem)) {
       constexpr std::string_view key = std::define_static_string(std::meta::identifier_of(mem));
-      // Note: removed static assert as optional types are now handled generically
+      if constexpr (concepts::optional_type<decltype(out.[:mem:])>) {
-      // as long we are succesful or the field is not found, we continue
+        // for optional members, it's ok if the key is missing
-      if(e == simdjson::SUCCESS || e == simdjson::NO_SUCH_FIELD) {
+        auto error = obj[key].get(out.[:mem:]);
-        e = obj[key].get(out.[:mem:]);
+        if (error && error != NO_SUCH_FIELD) {
+          if(error == NO_SUCH_FIELD) {
+            out.[:mem:].reset();
+            continue;
+          }
+          return error;
+        }
+      } else {
+        // for non-optional members, the key must be present
+        SIMDJSON_TRY(obj[key].get(out.[:mem:]));
       }
     }
   };
-  return e;
+  return simdjson::SUCCESS;
 }
 
 // Support for enum deserialization - deserialize from string representation using expand approach from P2996R12

include/simdjson/simdjson_version.h

@@ -4,7 +4,7 @@
 #define SIMDJSON_SIMDJSON_VERSION_H
 
 /** The version of simdjson being used (major.minor.revision) */
-#define SIMDJSON_VERSION "4.0.2"
+#define SIMDJSON_VERSION "4.0.6"
 
 namespace simdjson {
 enum {
@@ -19,7 +19,7 @@ enum {
   /**
    * The revision (major.minor.REVISION) of simdjson being used.
    */
-  SIMDJSON_VERSION_REVISION = 2
+  SIMDJSON_VERSION_REVISION = 6
 };
 } // namespace simdjson
 

singleheader/simdjson.cpp

@@ -1,4 +1,4 @@
-/* auto-generated on 2025-09-14 09:01:41 -0600. version 4.0.2 Do not edit! */
+/* auto-generated on 2025-09-20 22:23:09 -0600. version 4.0.6 Do not edit! */
 /* including simdjson.cpp:  */
 /* begin file simdjson.cpp */
 #define SIMDJSON_SRC_SIMDJSON_CPP
@@ -3009,11 +3009,32 @@ concept optional_type = requires(std::remove_cvref_t<T> obj) {
     } -> std::convertible_to<typename std::remove_cvref_t<T>::value_type>;
   };
   { static_cast<bool>(obj) } -> std::same_as<bool>; // convertible to bool
+  { obj.reset() } noexcept -> std::same_as<void>;
 };
 
 
 
+
+
 } // namespace concepts
+
+
+/**
+ * We use tag_invoke as our customization point mechanism.
+ */
+template <typename Tag, typename... Args>
+concept tag_invocable = requires(Tag tag, Args... args) {
+  tag_invoke(std::forward<Tag>(tag), std::forward<Args>(args)...);
+};
+
+template <typename Tag, typename... Args>
+concept nothrow_tag_invocable =
+    tag_invocable<Tag, Args...> && requires(Tag tag, Args... args) {
+      {
+        tag_invoke(std::forward<Tag>(tag), std::forward<Args>(args)...)
+      } noexcept;
+    };
+
 } // namespace simdjson
 #endif // SIMDJSON_SUPPORTS_CONCEPTS
 #endif // SIMDJSON_CONCEPTS_H

tests/builder/CMakeLists.txt

@@ -1,7 +1,8 @@
 # All remaining tests link with simdjson proper
 include_directories(..)
-add_cpp_test(builder_string_builder_tests              LABELS ondemand acceptance per_implementation)
+add_cpp_test(builder_string_builder_tests                LABELS ondemand acceptance per_implementation)
 if(SIMDJSON_STATIC_REFLECTION)
+  add_cpp_test(static_reflection_custom_tests            LABELS ondemand acceptance per_implementation)
   add_cpp_test(static_reflection_builder_tests           LABELS ondemand acceptance per_implementation)
   add_cpp_test(static_reflection_comprehensive_tests     LABELS ondemand acceptance per_implementation)
   add_cpp_test(static_reflection_edge_cases_tests        LABELS ondemand acceptance per_implementation)

tests/builder/builder_string_builder_tests.cpp

@@ -331,8 +331,6 @@ namespace builder_tests {
         TEST_SUCCEED();
     }
 
-
-
     void serialize_car(const Car& car, simdjson::builder::string_builder& builder) {
         // start of JSON
         builder.start_object();
@@ -369,7 +367,43 @@ namespace builder_tests {
         builder.end_object();
     }
 
+#if SIMDJSON_SUPPORTS_CONCEPTS
+    void serialize_car_template(const Car& car, simdjson::builder::string_builder& builder) {
+        // start of JSON
+        builder.start_object();
 
+        // "make"
+        builder.append_key_value<"make">(car.make);
+        builder.append_comma();
+
+        // "model"
+        builder.append_key_value<"model">(car.model);
+
+        builder.append_comma();
+
+        // "year"
+        builder.append_key_value<"year">(car.year);
+
+        builder.append_comma();
+
+        // "tire_pressure"
+        builder.escape_and_append_with_quotes<"tire_pressure">();
+        builder.append_colon();
+        builder.start_array();
+        // vector tire_pressure
+        for (size_t i = 0; i < car.tire_pressure.size(); ++i) {
+            builder.append(car.tire_pressure[i]);
+            if (i < car.tire_pressure.size() - 1) {
+                builder.append_comma();
+            }
+        }
+        // end of array
+        builder.end_array();
+
+        // end of object
+        builder.end_object();
+    }
+#endif
     bool car_test() {
         TEST_START();
         simdjson::builder::string_builder sb;
@@ -381,7 +415,18 @@ namespace builder_tests {
         ASSERT_EQUAL(p, "{\"make\":\"Toyota\",\"model\":\"Corolla\",\"year\":2017,\"tire_pressure\":[30.0,30.2,30.513,30.79]}");
         TEST_SUCCEED();
     }
-    #if SIMDJSON_SUPPORTS_CONCEPTS
+#if SIMDJSON_SUPPORTS_CONCEPTS
+    bool car_test_template() {
+        TEST_START();
+        simdjson::builder::string_builder sb;
+        Car c = {"Toyota", "Corolla", 2017, {30.0,30.2,30.513,30.79}};
+        serialize_car_template(c, sb);
+        std::string_view p;
+        auto result = sb.view().get(p);
+        ASSERT_SUCCESS(result);
+        ASSERT_EQUAL(p, "{\"make\":\"Toyota\",\"model\":\"Corolla\",\"year\":2017,\"tire_pressure\":[30.0,30.2,30.513,30.79]}");
+        TEST_SUCCEED();
+    }
     bool serialize_optional() {
         TEST_START();
         simdjson::builder::string_builder sb;
@@ -399,7 +444,7 @@ namespace builder_tests {
         ASSERT_EQUAL(p, "null");
         TEST_SUCCEED();
     }
-    #endif
+#endif
 
     #if SIMDJSON_SUPPORTS_RANGES && SIMDJSON_SUPPORTS_CONCEPTS
     void serialize_car_simple(const Car& car, simdjson::builder::string_builder& builder) {
@@ -474,6 +519,20 @@ namespace builder_tests {
         ASSERT_EQUAL(s, "[[1.0,2.0],[3.0,4.0]]");
         TEST_SUCCEED();
     }
+    bool double_double_test_to_string() {
+        TEST_START();
+        std::vector<std::vector<double>> c = {{1.0, 2.0}, {3.0, 4.0}};
+        simdjson::builder::string_builder sb;
+        sb.append(c);
+        std::string_view p;
+        auto result = sb.view().get(p);
+        ASSERT_SUCCESS(result);
+        ASSERT_EQUAL(p, "[[1.0,2.0],[3.0,4.0]]");
+        std::string s;
+        simdjson::simdjson_error ec = simdjson::to_json(c,s);
+        ASSERT_EQUAL(s, "[[1.0,2.0],[3.0,4.0]]");
+        TEST_SUCCEED();
+    }
     #if SIMDJSON_EXCEPTIONS
     bool car_test_simple_complete_exceptions() {
         TEST_START();
@@ -522,6 +581,7 @@ namespace builder_tests {
     #if SIMDJSON_SUPPORTS_RANGES && SIMDJSON_SUPPORTS_CONCEPTS
             map_test() &&
             double_double_test() &&
+            double_double_test_to_string() &&
             car_test_simple() &&
             car_test_simple_complete() &&
         #if SIMDJSON_EXCEPTIONS
@@ -529,7 +589,8 @@ namespace builder_tests {
         #endif
     #endif
     #if SIMDJSON_SUPPORTS_CONCEPTS
-           serialize_optional() &&
+            car_test_template() &&
+            serialize_optional() &&
     #endif
             append_char() &&
             append_integer() &&

tests/builder/static_reflection_custom_tests.cpp

@@ -0,0 +1,138 @@
+
+
+
+#include "simdjson.h"
+#include "test_builder.h"
+#include <charconv>
+#include <string>
+
+using namespace simdjson;
+
+// Suppose that we want to serialize/deserialize Car using
+// strings for the year
+struct Car {
+  std::string make;
+  std::string model;
+  int64_t year;
+  std::vector<float> tire_pressure;
+};
+
+
+
+namespace simdjson {
+// This tag_invoke MUST be inside simdjson namespace
+template <typename simdjson_value>
+auto tag_invoke(deserialize_tag, simdjson_value &val, Car& car) {
+  ondemand::object obj;
+  auto error = val.get_object().get(obj);
+  if (error) {
+    return error;
+  }
+  if ((error = obj["make"].get_string(car.make))) {
+    return error;
+  }
+  if ((error = obj["model"].get_string(car.model))) {
+    return error;
+  }
+  std::string_view year_str;
+  if ((error = obj["year"].get(year_str))) {
+    return error;
+  }
+  int64_t year_value;
+  auto [ptr, ec] = std::from_chars(year_str.data(), year_str.data() + year_str.size(), year_value);
+  if (ec != std::errc{}) {
+    return INCORRECT_TYPE;
+  }
+  car.year = year_value;
+  if ((error = obj["tire_pressure"].get<std::vector<float>>().get(
+           car.tire_pressure))) {
+    return error;
+  }
+  return simdjson::SUCCESS;
+}
+
+template <typename builder_type>
+void tag_invoke(serialize_tag, builder_type &builder, const Car& car) {
+  builder.start_object();
+  builder.append_key_value("make", car.make);
+  builder.append_comma();
+  builder.append_key_value("model", car.model);
+  builder.append_comma();
+  builder.append_key_value("year", std::to_string(car.year));
+  builder.append_comma();
+  builder.append_key_value("tire_pressure", car.tire_pressure);
+  builder.end_object();
+}
+
+} // namespace simdjson
+namespace custom_tests {
+
+  bool test_car_deserialization() {
+    TEST_START();
+    auto json = R"({"make":"Toyota","model":"Camry","year":"2018","tire_pressure":[30.5,30.6,30.7,30.8]})"_padded;
+    ondemand::parser parser;
+    auto doc_result = parser.iterate(json);
+    ASSERT_SUCCESS(doc_result);
+    Car car;
+    ASSERT_SUCCESS(doc_result.get(car));
+    if (car.make != "Toyota" || car.model != "Camry" || std::to_string(car.year) != "2018" || car.tire_pressure.size() != 4 || car.tire_pressure[0] != 30.5f) {
+      return false;
+    }
+    TEST_SUCCEED();
+  }
+  bool test_car_serialization() {
+    TEST_START();
+    Car car{"Toyota", "Camry", 2018, {30.5f,30.6f,30.7f,30.8f}};
+    simdjson::builder::string_builder builder;
+    builder.append(car);
+    std::string_view json;
+    ASSERT_SUCCESS(builder.view().get(json));
+    TEST_SUCCEED();
+  }
+  bool test_car_roundtrip() {
+    TEST_START();
+    Car car{"Toyota", "Camry", 2018, {30.5f,30.6f,30.7f,30.8f}};
+    simdjson::builder::string_builder builder;
+    builder.append(car);
+    std::string json;
+    ASSERT_SUCCESS(builder.view().get(json));
+    ondemand::parser parser;
+    auto doc_result = parser.iterate(json);
+    ASSERT_SUCCESS(doc_result);
+    Car carback;
+    ASSERT_SUCCESS(doc_result.get(carback));
+
+    if (carback.make != car.make || carback.model != car.model || carback.year != car.year || carback.tire_pressure != car.tire_pressure) {
+      return false;
+    }
+
+    TEST_SUCCEED();
+  }
+
+  bool test_car_roundtrip_to_json() {
+    TEST_START();
+    Car car{"Toyota", "Camry", 2018, {30.5f,30.6f,30.7f,30.8f}};
+    std::string json;
+    ASSERT_SUCCESS(simdjson::to_json(car).get(json));
+    simdjson::builder::string_builder builder;
+    ondemand::parser parser;
+    auto doc_result = parser.iterate(json);
+    ASSERT_SUCCESS(doc_result);
+    Car carback;
+    ASSERT_SUCCESS(doc_result.get(carback));
+
+    if (carback.make != car.make || carback.model != car.model || carback.year != car.year || carback.tire_pressure != car.tire_pressure) {
+      return false;
+    }
+
+    TEST_SUCCEED();
+  }
+  bool run() {
+    return test_car_deserialization() && test_car_serialization() && test_car_roundtrip() && test_car_roundtrip_to_json();
+  }
+
+} // namespace builder_tests
+
+int main(int argc, char *argv[]) {
+  return test_main(argc, argv, custom_tests::run);
+}

tests/dom/CMakeLists.txt

@@ -123,7 +123,7 @@ endif()
 
 # Add the tests if we're on:
 #   1. Visual Studio 2022 v17.6 or later
-#   2. GCC v14.0.0 or later (GCC v13.0.0 cannot handle pipe oprator of lambda)
+#   2. GCC v14.0.0 or later (GCC v13.0.0 cannot handle pipe operator of lambda)
 #   3. Clang v15.0.0 or later (certain version C++ headers occur error when compiling)
 if(
   (MSVC AND MSVC_VERSION LESS 1930) OR

tests/ondemand/ondemand_convert_tests.cpp

@@ -2,6 +2,7 @@
 #include "simdjson/convert.h"
 #include "test_ondemand.h"
 
+#include <chrono>
 #include <map>
 #include <ranges>
 #include <string>
@@ -21,6 +22,24 @@ private:
     std::string date_str;
 };
 
+
+struct Meeting {
+    std::string title;
+    std::vector<std::string> attendees;
+    std::optional<std::string> location;
+    bool is_recurring;
+};
+
+
+struct MeetingTime {
+    std::string title;
+    std::chrono::system_clock::time_point start_time;
+    std::vector<std::string> attendees;
+    std::optional<std::string> location;
+    bool is_recurring;
+};
+
+
 namespace simdjson {
 template <typename simdjson_value>
 auto tag_invoke(deserialize_tag, simdjson_value &val, MyDate& date) {
@@ -43,57 +62,6 @@ struct complicated_weather_data {
 #ifdef __cpp_lib_ranges
 
 namespace convert_tests {
-#if SIMDJSON_EXCEPTIONS && SIMDJSON_SUPPORTS_CONCEPTS
-struct Car {
-  std::string make{};
-  std::string model{};
-  int year{};
-  std::vector<double> tire_pressure{};
-
-  friend simdjson::error_code tag_invoke(simdjson::deserialize_tag, auto &val,
-                                         Car &car) {
-    simdjson::ondemand::object obj;
-    auto error = val.get_object().get(obj);
-    if (error) {
-      return error;
-    }
-    // Instead of repeatedly obj["something"], we iterate through the object
-    // which we expect to be faster.
-    for (auto field : obj) {
-      simdjson::ondemand::raw_json_string key;
-      error = field.key().get(key);
-      if (error) {
-        return error;
-      }
-      if (key == "make") {
-        error = field.value().get_string(car.make);
-        if (error) {
-          return error;
-        }
-      } else if (key == "model") {
-        error = field.value().get_string(car.model);
-        if (error) {
-          return error;
-        }
-      } else if (key == "year") {
-        error = field.value().get(car.year);
-        if (error) {
-          return error;
-        }
-      } else if (key == "tire_pressure") {
-        error = field.value().get(car.tire_pressure);
-        if (error) {
-          return error;
-        }
-      }
-    }
-    return simdjson::SUCCESS;
-  }
-};
-
-static_assert(simdjson::custom_deserializable<std::unique_ptr<Car>>,
-              "It should be deserializable");
-
 
 simdjson::padded_string json_car =
     R"( {
@@ -111,22 +79,114 @@ simdjson::padded_string json_cars =
        "tire_pressure": [ 29.8, 30.0 ] }
 ])"_padded;
 
-bool simple() {
+#if SIMDJSON_SUPPORTS_CONCEPTS
-  TEST_START();
+  struct Car {
-  Car car = simdjson::from(json_car);
+    std::string make{};
-  if (car.make != "Toyota" || car.model != "Camry" || car.year != 2018) {
+    std::string model{};
-    return false;
+    int year{};
+    std::vector<double> tire_pressure{};
+
+    friend simdjson::error_code tag_invoke(simdjson::deserialize_tag, auto &val,
+                                          Car &car) {
+      simdjson::ondemand::object obj;
+      auto error = val.get_object().get(obj);
+      if (error) {
+        return error;
+      }
+      // Instead of repeatedly obj["something"], we iterate through the object
+      // which we expect to be faster.
+      for (auto field : obj) {
+        simdjson::ondemand::raw_json_string key;
+        error = field.key().get(key);
+        if (error) {
+          return error;
+        }
+        if (key == "make") {
+          error = field.value().get_string(car.make);
+          if (error) {
+            return error;
+          }
+        } else if (key == "model") {
+          error = field.value().get_string(car.model);
+          if (error) {
+            return error;
+          }
+        } else if (key == "year") {
+          error = field.value().get(car.year);
+          if (error) {
+            return error;
+          }
+        } else if (key == "tire_pressure") {
+          error = field.value().get(car.tire_pressure);
+          if (error) {
+            return error;
+          }
+        }
+      }
+      return simdjson::SUCCESS;
+    }
+  };
+
+  static_assert(simdjson::custom_deserializable<std::unique_ptr<Car>>,
+                "It should be deserializable");
+
+
+  bool simple_no_except() {
+    TEST_START();
+    Car car;
+    ASSERT_SUCCESS(simdjson::from(json_car).get(car));
+    if (car.make != "Toyota" || car.model != "Camry" || car.year != 2018) {
+      return false;
+    }
+    TEST_SUCCEED();
   }
-  TEST_SUCCEED();
+#endif // SIMDJSON_SUPPORTS_CONCEPTS
-}
+#if SIMDJSON_EXCEPTIONS && SIMDJSON_SUPPORTS_CONCEPTS
-
 
+  bool simple() {
+    TEST_START();
+    Car car = simdjson::from(json_car);
+    if (car.make != "Toyota" || car.model != "Camry" || car.year != 2018) {
+      return false;
+    }
+    TEST_SUCCEED();
+  }
+  struct Player {
+      std::string username;
+      int level;
+      double health;
+  };
   struct BadPlayer {
       int username;  // Oops, should be string!
       int level;
       double health;
   };
+  struct OptionalPlayer {
+      std::string username;
+      std::optional<int> level;
+      double health;
+  };
 #if SIMDJSON_STATIC_REFLECTION
+  bool missing_key_player() {
+    TEST_START();
+    std::string json = R"({"username":"Alice","health":100.0})";
+    simdjson::padded_string padded(json);
+    Player p;
+    simdjson::ondemand::parser parser;
+    auto doc = parser.iterate(padded);
+    ASSERT_ERROR(doc.get(p), simdjson::NO_SUCH_FIELD);
+    TEST_SUCCEED();
+  }
+  bool missing_key_optional_player() {
+    TEST_START();
+    std::string json = R"({"username":"Alice","health":100.0})";
+    simdjson::padded_string padded(json);
+    OptionalPlayer p;
+    simdjson::ondemand::parser parser;
+    auto doc = parser.iterate(padded);
+    ASSERT_SUCCESS(doc.get(p));
+    TEST_SUCCEED();
+  }
   bool bad_player() {
     TEST_START();
     // username is a string but we declared it as an int
@@ -160,6 +220,38 @@ bool simple() {
     ASSERT_SUCCESS(doc.get(p));
     TEST_SUCCEED();
   }
+
+
+  bool meeting_test() {
+    TEST_START();
+    std::string json = simdjson::to_json(Meeting{
+        .title = "CppCon Planning",
+        .attendees = {"Alice", "Bob", "Charlie"},
+        .location = "Denver",
+        .is_recurring = true
+    });
+    Meeting m2 = simdjson::from(json);
+    std::cout << m2.title << std::endl;
+    TEST_SUCCEED();
+  }
+  bool meeting_time_test() {
+    TEST_START();
+    auto start_time = std::chrono::system_clock::now();
+    std::string json = simdjson::to_json(MeetingTime{
+        .title = "CppCon Planning",
+        .start_time = start_time,
+        .attendees = {"Alice", "Bob", "Charlie"},
+        .location = "Denver",
+        .is_recurring = true
+    });
+    std::cout << json << std::endl;
+    MeetingTime m2 = simdjson::from(json);
+    //ASSERT_EQUAL(m2.start_time, start_time);
+    std::cout << m2.title << std::endl;
+    TEST_SUCCEED();
+  }
+
+
 #endif
 bool broken() {
   TEST_START();
@@ -415,7 +507,10 @@ bool test_to_vs_from_equivalence() {
 bool run() {
   return
 #if SIMDJSON_STATIC_REFLECTION
-      bad_player() && good_player() && complicated_weather_test() &&
+      missing_key_optional_player() && missing_key_player() && meeting_time_test() && meeting_test() && bad_player() && good_player() && complicated_weather_test() &&
+#endif
+#if SIMDJSON_SUPPORTS_CONCEPTS
+      simple_no_except() &&
 #endif
 #if SIMDJSON_EXCEPTIONS && SIMDJSON_SUPPORTS_CONCEPTS
       broken() && simple() && simple_optional() && with_parser() && to_array() &&