Release date: 2022-01-03

SHA-256: e832d339d9e0c042e7dff807754769d778cf5d6ae9730ce21eed56de99cb5e86 (json.hpp), b94997df68856753b72f0d7a3703b7d484d4745c567f3584ef97c96c25a5798e (include.zip)

The previous version 3.10.4 introduced support to convert **`std::filesystem`** objects to JSON and vice versa. Unfortunately, we made the assumption that any compiler supporting C++17 would also have proper filesystem support. This was a mistake. This release introduces preprocessor checks  (and means to override them) to make sure that the conversion support is only compiled if the compiler is detected to support it.

All changes are backward-compatible.

:moneybag: Note you can **support this project** via [GitHub sponsors](https://github.com/sponsors/nlohmann) or [PayPal](http://paypal.me/nlohmann).

- Make sure C++17 filesystem conversions are only used if the compiler supports it. Furthermore, add defines  [`JSON_HAS_FILESYSTEM` and `JSON_HAS_EXPERIMENTAL_FILESYSTEM`](https://json.nlohmann.me/features/macros/#json_has_cpp_11-json_has_cpp_14-json_has_cpp_17-json_has_cpp_20) which can be set to `0` to avoid using filesystem support altogether.`std::filesystem`. #3090 #3097 #3101 #3156 #3203
- Fix a compilation error with Nvidia CUDA Compiler (NVCC).  #3013 #3234

- Fix a warning for shadowed variables. #3188 #3193
- Fix a warning on a pointless comparison. #3227 #2712 #2676 #1390 #755

- Add a parameter to the [`update`](https://json.nlohmann.me/api/basic_json/update/) function to recursively merge objects with common keys. #3006 #3069
- Extend [`std::hash`](https://json.nlohmann.me/api/basic_json/std_hash/#version-history) and [`std::swap`](https://json.nlohmann.me/api/basic_json/std_swap/) to work on any `nlohmann::basic_json` specializations rather than just `nlohmann::json`. #3121

- Update CI to use Clang 14, GCC 6, and Clang-Tidy 14. #3088
- Update cpplint. #3225
- Add build step for the Nvidia CUDA Compiler (NVCC). #3227
- Remove Travis CI. #3087 #3233
- Compile and execute the test suite with C++17. #3101

- The [mkdocs](https://www.mkdocs.org)-based documentation in [doc/mkdocs](https://github.com/nlohmann/json/tree/develop/doc/mkdocs) has been totally overworked. It now has a unified structure, more examples, and contains all information from the previous Doxygen-based documentation. The single source of truth is now the documentation on <https://json.nlohmann.me> and in particular the [**API Documentation**](https://json.nlohmann.me/api/basic_json/). #3071
- Removed Wandbox online examples. #3071
- Fix typos, links, and parameter names in the documentation. #3102 #3125 #3140 #3145 #3148
- Add more examples. #3071 #3100

Passing iterator pairs or pointer/length pairs to parsing functions (`basic_json::parse`, `basic_json::accept`, `basic_json::sax_parse`, `basic_json::from_cbor`, `basic_json::from_msgpack`, `basic_json::from_ubjson`, `basic_json::from_bson`) via initializer lists is deprecated. Instead, pass two iterators; for instance, call `basic_json::from_cbor(ptr, ptr+len)` instead of `basic_json::from_cbor({ptr, len})`.

The following functions have been deprecated in earlier versions and will be removed in the next major version (i.e., 4.0.0):

- Function [`iterator_wrapper`](https://nlohmann.github.io/json/doxygen/classnlohmann_1_1basic__json_a0a8051760196ac813fd5eb3c8d5a2976.html#a0a8051760196ac813fd5eb3c8d5a2976) are deprecated. Please use the member function [`items()`](https://nlohmann.github.io/json/doxygen/classnlohmann_1_1basic__json_a5961446010dfc494e0c247b4e9026977.html#a5961446010dfc494e0c247b4e9026977) instead.
- Functions [`friend std::istream& operator<<(basic_json&, std::istream&)`](https://nlohmann.github.io/json/doxygen/classnlohmann_1_1basic__json_a60ca396028b8d9714c6e10efbf475af6.html#a60ca396028b8d9714c6e10efbf475af6) and [`friend std::ostream& operator>>(const basic_json&, std::ostream&)`](https://nlohmann.github.io/json/doxygen/classnlohmann_1_1basic__json_a34d6a60dd99e9f33b8273a1c8db5669b.html#a34d6a60dd99e9f33b8273a1c8db5669b) are deprecated. Please use [`friend std::istream&  operator>>(std::istream&, basic_json&)`](https://nlohmann.github.io/json/doxygen/classnlohmann_1_1basic__json_aaf363408931d76472ded14017e59c9e8.html#aaf363408931d76472ded14017e59c9e8) and [`friend operator<<(std::ostream&, const basic_json&)`](https://nlohmann.github.io/json/doxygen/classnlohmann_1_1basic__json_a5e34c5435e557d0bf666bd7311211405.html#a5e34c5435e557d0bf666bd7311211405) instead.

All deprecations are annotated with [`HEDLEY_DEPRECATED_FOR`](https://nemequ.github.io/hedley/api-reference.html#HEDLEY_DEPRECATED_FOR) to report which function to use instead.