JSON for Modern C++

Release date: 2022-08-01 SHA-256: eb73896e9ce706ae6a62ce697dc8aca214840f70d8281779a6ea0cabe3afab3f (json.hpp), b4789050cacd110faf8b100cee82af19ad0b4d3249625f6582a60eeeb80c84a7 (include.zip), 5c8f7a4d9e9c0d565e71b6e5b0b3a12f784ffbf142e1ddc7ba86002cefb4c6ee (json.tar.xz)

Summary

Version 3.11.0 is one of the biggest releases (in terms of closed issues and merged pull requests) ever. It brings:

• String view support for all functions working on object keys (e.g., at or operator[]), avoiding unnecessary allocations.
• BJData as the fifth supported binary format besides BSON, CBOR, MessagePack, and UBJSON.
• Better C++20 support to make the library integrate more smoothly with newer codebases.
• Better support for avoiding problems when multiple versions of the library are used in the same project.
• Even better and more extensive documentation and examples.
• More tests for edge cases like 32-bit support, C++20 features, using the library with ICPC, or after including <windows.h>.

All changes are backward-compatible.

:moneybag: Note you can support this project via GitHub sponsors or PayPal.

:sparkles: New Features

• Allow to use std::string_view as object keys in at, operator[], value, erase, find, contains, and count to avoid unnecessary allocations. #3423, #1529, #3558, #3564
• Add support to read and write the UBJSON-derived Binary JData (BJData) format (see documentation). #3336, #3461, #3463, #3475, #3479, #3493, #3491, #3492, #3490, #3500, #3502, #3503, #3505, #3513, #3514, #3519, #3523, #3541, #3543

:bug: Bug fixes

• Allow creation of ordered_json objects from initializer lists. #3342, #3343, #3370
• Fix failing tests when compiling with C++20 and add support for operator<=>. #3207, #3446, #3472
• Fix comparison-related compilation problems in C++20 on GCC 12. #3138, #3379
• Make iterator satisfy std::incrementable. #3331, #3332
• Exclude std::any from implicit conversion. #3428, #3437
• Fix constraints on from_json() for strings. #3171, #3267, #3312, #3384, #3427, #3312, #3620
• Make iterators usable with <ranges> and range-v3. #3130, #3446
• Fix comparison of NaN values with json to behave like float. #3409, #3446
• Add operator<<(json_pointer) to fix a regression after the 3.10.0 release. #3600, #3601
• Fix JSON Patch to not create missing parent objects. #3134, #3199, #3628
• Re-add value_type detection to distinguish string types (was broken in releases 3.10.4, and 3.10.5). #3204, #3333, #3604, #3602, #3629
• Fix latest build error in MSVC platform (was broken during development of 3.11.0). #3630

:zap: Improvements

• Allow default values for NLOHMANN_DEFINE_TYPE_INTRUSIVE and NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE. #2819, #3143
• Avoid clash with Arduino defines. #3338
• Improve meta output for MSVC. #3417
• Check and warn if a different version of the library is already included (see JSON_SKIP_LIBRARY_VERSION_CHECK). #3418
• Re-template json_pointer on string type. #3415
• Allow to create booleans from std::vector<bool>::reference. #3533, #3534
• Allow to use array types where iterators are pointers. #3544
• Improve performance of writing binary formats to byte vectors. #3569
• Add patch_inplace function to apply patches without copying. #3581, #3596
• Use swap by ADL to allow swapping with non-std containers and improve error messages. #3609
• Add versioned, ABI-tagged inline namespace (see NLOHMANN_JSON_NAMESPACE) to avoid ODR errors when linking different versions of the library. #1539, #3360, #3588, #3590
• Move UDLs out of the global namespace (see JSON_USE_GLOBAL_UDLS) to avoid name clashes. #1682, #3605

Warnings

• Fix ICPC warning 1098. #3632, #3634
• Fix a -Wpragmas warning in GCC <11. #3550

:hammer: Further Changes

• Fix _MSC_VER version to check for std::filesystem. #3240
• Remove <sstream> dependency. #3239, #3244
• Overwork bug template to systematically request information. #3348
• Add script to test local version in Compiler Explorer. #3456
• Change the default value of the CMake parameter JSON_MultipleHeader to ON to always use the multi-header version unless specified otherwise. #3532
• Add option to disable default enum conversions (see JSON_DISABLE_ENUM_SERIALIZATION). #3536
• Add maintainer targets to create source archive json.tar.xz which can be used in FetchContent. #3289, #3255
• Fix CITATION.cff. #3320
• Use The Pitchfork Layout (PFL). #3462
• Update Cpplint. #3454
• More intermediate folders from Visual Studio Code are added to .gitignore. #3572
• Add badge for https://repology.org/project/nlohmann-json/versions. #3586
• Use REUSE licensing framework. #3546 , #3633, #3635
• Install .pc and .cmake files to share directory. #3619

CI

• Add support for Visual Studio 2022., #3295
• Adjust GitHub Actions CI wrt. windows-latest image. #3368
• Remove deprecated windows-2016 image. #3416
• Speed up AppVeyor CI. #3422
• Update CI image to check with ICPC, GCC 11 and Clang 14. #3420
• Add build step for ICPC to CI. #3465
• Add more Xcode versions (13.3.1, 13.3, 13.2.1, 13.2, and 13.1) to the CI. #3485
• Fix "JSON_MultipleHeaders" option spelling in CI. #3555
• Increase timeout for Unicode tests. #3579, #3580, #3614
• Abort CI runs on newer commits on the same branch. #3610
• Fix MinGW CI failures. #3618
• Disable exceptions on ICPC (for the disabled_exceptions unit test). #3621

Unit tests

• Improve unit tests. #3380, #3393, #3365, #3405, #3377, #3421, #3422
• Disable regression test on GCC <8.4. #3451
• Add tests for 32 bit. #3524, #3529, #3530, #3532
• Add error message if test suite cannot be found. #3584, #3585
• Add unit test to make sure iterator_input_adapter advances iterators correctly. #3548
• Add a unit test including <windows.h>. #3631

Documentation and examples

• Add more examples to documentation. #3464
• Improve documentation on supported types of parse and accept. #3245, #3246
• Add documentation on how to parse JSON Lines input. #3247
• Fix typos. #3249, #3265, #3426, #3439, #3481, #3499
• Document parsing to ordered_json. #3325, #3326
• Use FetchContent_MakeAvailable in examples. #3345, #3351
• Document requirement of using the same definition of JSON_DIAGNOSTICS in all linked objects. #3360, #3378
• Document fuzz testing. #3477, #3478
• Add documentation of macros and runtime assertions. #3444, #3431
• Fix documentation of JSON Pointer. #3511, #3520
• Make certain usage patterns more prominent in the README. #3557
• Document precondition for parsing from FILE * and add assertion. #3593
• Improve documentation. #3592
• Add documentation for comparing json and ordered_json. #3443, #3599
• Adjust JSON Pointer examples and add CI step for the examples. #3622
• Overwork documentation and add more examples. #3553

:fire: Deprecated functions

The implicit conversion from JSON Pointers to string (json_pointer::operator string_t) has been deprecated. Use json_pointer::to_string instead.

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

• The function iterator_wrapper is deprecated. Please use the member function items() instead.
• Functions friend std::istream& operator<<(basic_json&, std::istream&) and friend std::ostream& operator>>(const basic_json&, std::ostream&) are deprecated. Please use friend std::istream& operator>>(std::istream&, basic_json&) and friend operator<<(std::ostream&, const basic_json&) instead.
• 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}).

All deprecations are annotated with HEDLEY_DEPRECATED_FOR to report which function to use instead.