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Author SHA1 Message Date
Niels LohmannandMuhammad Amir bin Mohamad Ghazaly 8c1f60a45e Store maps with enum keys as objects (opt-in) (#5600) 
* Store maps with enum keys as objects (opt-in)

Maps with enum keys, such as std::map<E, T>, are stored as arrays of
[key, value] pairs, because enums are not convertible to the string type
of object keys - even if NLOHMANN_JSON_SERIALIZE_ENUM maps them to
strings (#4378).

The new JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS macro stores them as objects
instead, converting each key with the enum's to_json. It applies to any
map-like type with enum keys (std::map with any comparator,
std::unordered_map, ...). A key that does not convert to a string throws
type_error.302, and two keys converting to the same string throw the new
type_error.318, rather than losing an entry. The macro changes the output
of inline functions, so it is part of the ABI tag (_ekmo).

Reading needs no macro: std::map and std::unordered_map with enum keys
are now also read from objects, converting each key with the enum's
from_json. That input was rejected before, and arrays of pairs are still
read, so data written either way can be read.

This supersedes #4531, which first proposed storing these maps as
objects.

Co-authored-by: Muhammad Amir bin Mohamad Ghazaly <amirghaz@umich.edu>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Keep multimaps with enum keys as arrays of pairs

With JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS, is_enum_keyed_map also matched
std::multimap and std::unordered_multimap. Storing them as objects throws
type_error.318 as soon as a key occurs twice, which is the normal case for
a multimap, so such values could no longer be serialized at all once the
macro was enabled, although they are stored losslessly as arrays of
[key, value] pairs without it.

Exclude maps with non-unique keys from is_enum_keyed_map. They are
detected by insert(value_type) returning an iterator rather than a
pair<iterator, bool>. Map-like types without such an insert() are still
treated as before.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Move the default enum-keyed map tests out of unit-conversions.cpp

The Windows clang 20.1.8 job (MinGW, Debug) failed to link
test-conversions_cpp17 with "relocation truncated to fit:
IMAGE_REL_AMD64_REL32 against .rdata": the object file of
unit-conversions.cpp was already close to the limit, and the new
"maps with enum keys" test case pushed it over. windows.yml asks to keep
these objects small by splitting test files.

Move the test case unchanged into unit-enum_keyed_maps_default.cpp,
with the three enums it needs. It still honors a -D flag for
JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS, as before. unit-conversions.cpp
is back to its state on develop.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Build the enum-keyed map test object instead of parsing it

ci_test_diagnostic_positions failed in unit-enum_keyed_maps_default.cpp:
with JSON_DIAGNOSTIC_POSITIONS, a parsed value adds its byte range to
the exception message ("(bytes 0-7) type must be array, but is
object"), so the exact-message checks did not match. Build the object
in memory, like unit-custom-array-type.cpp does.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Muhammad Amir bin Mohamad Ghazaly <amirghaz@umich.edu>
 2026-10-04 17:54:05 +02:00
Niels Lohmann d8d47be4a5 Fix CI on develop after merging the ready-to-merge PRs (#5754) 
* Keep the serializer conversion for objects whose keys cannot be converted

#5591 added a test converting nlohmann::json into a basic_json whose
string type cannot be constructed from std::string. That instantiates
convert_iteratively(), whose members.emplace_back(next.key(), ...) needs
exactly that key conversion, and broke the build of unit-alt-string.
Dispatch on the key's constructibility and leave such conversions to the
serializers, as the levels above the nesting bound already do (#3425).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix the remaining CI failures on develop

- unit-wstring: with a 16-bit wchar_t (Windows), a lone surrogate is
  reported as the ill-formed byte 0xFF since #5704; the std::wstring
  expectations still had the previous <U+0000>.
- ci_single_binaries: json_literals.hpp (#5610) and json.hpp include each
  other on purpose, and IWYU, not following the cycle, asks to replace
  json.hpp with json_fwd.hpp. Report its findings without failing the
  build, as already done for json.hpp.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix the library warnings and noexcept specifications from the merged PRs

- binary_reader: rename the error_handler constructor parameter, which
  shadowed the member (-Wshadow, -Wshadow-field-in-constructor; #5746)
- basic_json(copy_construct_tag, ...): declare it noexcept when copying
  the base class is (GCC 16 -Wnoexcept; #5690)
- the scalar-on-left legacy comparison operators: noexcept only when
  converting the scalar is, like their member counterparts (#5682, #5751)
- compare_leaves: use std::is_eq/is_lt/is_gt instead of comparing a
  std::partial_ordering with 0 (-Wzero-as-null-pointer-constant; #5686)
- serializer: silence MSVC C4127 for the EnsureAscii template parameter
  (#5741, #5746)
- clang-tidy: return the sanitized reference in binary_writer, take the
  key of ordered_map::find_impl by const reference (#5727), and mark the
  switches over parse_array_index (#5728)
- ordered_map: keep <memory> for std::allocator (IWYU)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Split unit-conversions.cpp so MinGW can link it

clang 18 with the MinGW linker failed to link test-conversions_cpp17
("relocation truncated to fit: IMAGE_REL_AMD64_REL32"). As windows.yml
recommends, keep the objects small by splitting the test file.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix the tests added by the merged PRs for all CI configurations

- discard the results of dump() and from_*() in CHECK_THROWS with
  utils::ignore_return_value (GCC -Werror=unused-result)
- give unit-bson's huge_string_t a default constructor (MSVC C2512,
  GCC 5, clang 3.5)
- unit-disabled_exceptions: use the literals namespace when the global
  UDLs are off (ci_test_noglobaludls; #5700)
- unit-binary_utf8_strict: expect the JSON pointer prefix with
  JSON_DIAGNOSTICS (#5741)
- skip the tests that rely on exceptions under JSON_NOEXCEPTION
  (#5678, #5732)
- clang-tidy and clang -Werror: static test data, CAPTURE(...);,
  const-correctness, use-after-move alias, unused conversion operator,
  a missing <iterator> include

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Title the macro examples and add JSON_STRICT_BINARY_UTF8 to the docset

The documentation style check requires "Example: ..." titles on pages with several examples (#5741, #5591) and a docset entry for every macro page.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Regenerate BUILD.bazel and nlohmann_json.natvis

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

#5746 added detail/output/error_handler.hpp and #5741 the json_abi_sbu8 ABI tag.

* Install libidn11 for the CMake 3.5.0 binary in ci_cmake_flags

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

#5733 moved ci_cmake_options from ubuntu:focal to ubuntu:24.04, which no longer ships libidn.so.11; the CMake 3.5.0 release binary links against it, so every ci_cmake_flags run has failed since. Install focal's libidn11 package for that matrix entry only.

* Suppress Infer's false STACK_VARIABLE_ADDRESS_ESCAPE in get_impl

get_impl() returns its local by value. A test added by the merged PRs instantiates it with a type Infer misreads, so ci_infer reported the 2021 code for the first time.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
 2026-10-04 17:18:19 +02:00
Niels Lohmann 1e44262091 Make JSON_STRICT_NUL_HANDLING part of the ABI tag (#5560) 
* Make JSON_STRICT_NUL_HANDLING part of the ABI tag

JSON_STRICT_NUL_HANDLING (#5534) changes the bodies of inline functions:
the lexer's handling of '\0' and input_adapter() for char arrays. So
translation units compiled with and without it define the same functions
differently, an ODR violation - the case the ABI tag exists for, as with
JSON_BRACE_INIT_COPY_SEMANTICS (_bics). It now appends _snul to the inline
namespace. The macro is new in 3.13.0, so no existing namespace changes.

Its default moves to abi_macros.hpp, and it is only #undef'd without
JSON_TEST_KEEP_MACROS, as for the other ABI macros. The ABI config tests,
the namespace docs, the macro's docs and the Natvis file cover the new tag.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Amalgamate

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
 2026-09-25 21:54:11 +02:00
Niels Lohmann abbe52d6de Add JSON_PRECISE_STREAM_POSITION to leave the character that terminates a number in the stream (#5344) 
* docs: qualify the operator>> stream positioning guarantee

operator>>'s notes state that it leaves the stream positioned right
after the parsed value, so that concatenated JSON values can be read
back to back. That does not hold when the value is a number: a number
is only terminated by the character that follows it, and the lexer's
unget() is simulated (it rewinds only the lexer's own bookkeeping),
so that character stays consumed from the stream.

Document the actual behaviour: the guarantee holds for all value types
except numbers, which must be followed by whitespace. Also qualify the
cross-reference on the JSON Lines page, which repeated the unqualified
claim.

Documentation only; the behaviour itself is tracked in #5340.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* fix: restore the character that terminates a number (#5340)

operator>> is documented to leave the stream positioned right after the
parsed value, so that concatenated JSON values can be read back to back.
That did not hold for numbers: a number is only terminated by the
character following it, and lexer::scan_number() reads that character
and calls unget() -- which is simulated and rewinds only the lexer's own
bookkeeping. input_stream_adapter consumes via sbumpc() with no matching
sungetc(), so the terminating character stayed consumed and the next
extraction started one byte too late ('1true' left the stream at 'rue').

Propagating unget() to the adapter directly does not work: next_unget
makes the following get() replay the cached character, so the terminator
would be delivered twice. Instead, restore the still-pending character
once at the end of a non-strict parse, where the input is handed back to
the caller:

- input_stream_adapter gains unget_character() (sungetc()) and advertises
  it via supports_unget, detected the same way as supports_seek.
- lexer::restore_pending_unget() turns a pending simulated unget of a
  real (non-EOF) character into a real one and clears next_unget so the
  character is not also replayed. It is a no-op for adapters that cannot
  unget, and reports failure when sungetc() fails, in which case the
  input is left as it was before.
- parser calls it on the three non-strict paths, i.e. for operator>> and
  sax_parse(strict = false).

Strict parse()/accept() are unaffected: they require the input to end
after the value, so the character is consumed by the end-of-input check
anyway. Parse error messages and reported positions are unchanged.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* tests: fix CI failures in the #5340 test helpers

Four CI failures, all in the new test code:

- GCC (-Werror=useless-cast): drop the `json(...)` wrapper around
  `json::parse(...)`, which already returns a `json`.
- GCC (-Werror=unused-result): assign the discarded `json::parse()`
  result to a dummy, the idiom used elsewhere in the test suite, and
  catch `json::parse_error&` for consistency.
- clang-tidy (google-default-arguments): remove the default argument
  from the `pbackfail()` override; `sungetc()` supplies the base
  declaration's default.
- MSVC (bad allocation): `no_putback_streambuf::underflow()` set a
  one-character get area without advancing `m_pos`, so an implementation
  whose `istream::get` peeks before it bumps re-read the same character
  forever. Keep no get area at all: `underflow()` peeks, `uflow()`
  consumes, and `sungetc()` still always lands in `pbackfail()`, which
  is what the test needs.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* fix: leave the character that terminates a number in the input

Read the character following a number without consuming it, instead of
consuming it and putting it back. input_stream_adapter now peeks with
sgetc() and only steps over the character when the next one is requested
or when the adapter is destroyed, so releasing it cannot fail - no
putback position is required from the streambuf.

Suggested by gregmarr in #5344.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* docs: match the version history wording to the peek-based fix

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* docs: drop the whitespace-separator caveat from the parsing pages

The caveat added in #5343 describes the behavior this branch fixes: a
number no longer consumes the character that terminates it, so
concatenated values need no separator.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* refactor: split the strict and non-strict paths in parser

Folding the release_lookahead() call into the existing strict check left
the "in strict mode" comment on an else-if branch, and made the strict
condition in sax_parse() redundant with the branch it followed.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Put the stream position fix behind JSON_PRECISE_STREAM_POSITION

Leaving the character that terminates a number in the stream is observable:
reading "1,2,3" with repeated operator>> works today only because the comma
after each number is swallowed, and std::getline after a number skips the
line break. Both break with the fix, so make it opt-in for 3.x, as suggested
by @gregmarr in the review.

- JSON_PRECISE_STREAM_POSITION (default 0) selects the peek-based
  input_stream_adapter. Without it, the adapter is the consuming one from
  develop and has no supports_lookahead, so lexer::release_lookahead() and
  the parser's calls to it compile to nothing.
- The macro changes input_stream_adapter's layout and member functions, so
  it gets the ABI tag _psp, after _bics. The ABI config tests, the natvis
  generator, and nlohmann_json.natvis (regenerated) know the tag.
- The tests for the fix move to unit-precise-stream-position.cpp, which
  defines the macro itself and runs in every build, and gain the two cases
  above. unit-deserialization.cpp pins the default behavior instead.
- The docs describe the default behavior again and point to the new macro
  page; version history says "added in 3.13.0, planned default in 4.0.0".

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
 2026-09-25 17:56:18 +02:00
Niels Lohmann 2e91641de2 Test JSON_BRACE_INIT_COPY_SEMANTICS for real, and fix one-element tuples under it (#5544) 
* Test JSON_BRACE_INIT_COPY_SEMANTICS for real, and fix one-element tuples under it

The opt-in JSON_BRACE_INIT_COPY_SEMANTICS was never exercised by CI:

- Its only test, in unit-regression3.cpp, was guarded by
  `#if defined(JSON_BRACE_INIT_COPY_SEMANTICS)` after the #include. The
  header #undefs the macro unconditionally in macro_unscope.hpp, so the
  guard was always false and the test compiled to nothing, whatever -D
  flag was passed.
- The ci_test_brace_init_copy_semantics target that passes the flag was
  not named by any workflow.

Move the test into its own translation unit that defines the macro before
including the header, as unit-diagnostics.cpp does for JSON_DIAGNOSTICS.
It now runs in every CI job and for every standard. Remove the unused
target: it ran the whole suite with the macro, and that suite deliberately
relies on default brace-init semantics in about 90 places
(e.g. `json({1})` meaning `[1]`), so it could never pass.

Running the whole suite with the macro did find one library bug:
to_json for std::tuple builds `j = { std::get<Idx>(t)... }`, so with copy
semantics a one-element tuple became its element. `json(std::tuple<int>{5})`
was `5` instead of `[5]`, and `get<std::tuple<int>>()` threw type_error.302
on the result. Under the macro, a one-element tuple now builds exactly what
the default deduction builds. Without the macro nothing changes.

The new tests also pin that the library's other conversions produce the
same values with and without the macro. The macro page now says that the
macro affects every single-element list (`json j = {1}` is `1`), and that
all translation units must agree on it, since it has no ABI tag.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Make JSON_BRACE_INIT_COPY_SEMANTICS part of the ABI tag

The macro changes the body of the initializer-list constructor and adds a
to_json_tuple_impl overload, both with the same mangled names in either
mode, so mixing translation units silently picked one definition. Encode
it in the inline namespace as `_bics`, as JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
does with `_ldvcmp`. The macro is new in the unreleased 3.13.0, so no
existing namespace name changes.

- Move the macro's default into abi_macros.hpp so json_fwd.hpp computes
  the same namespace, and keep it defined under JSON_TEST_KEEP_MACROS.
- Check the tag in the ABI config tests and in the unit test.
- List `_bics` (and the missing `_dp`) in the namespace docs and in the
  natvis generator; regenerate nlohmann_json.natvis.
- Replace the "define it consistently" warning with an ABI note.

Suggested by @gregmarr in the review of #5544.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix the cppcheck, clang-tidy and legacy-comparison CI failures

- to_json_tuple_impl() moved the element in both branches of a ternary;
  only one runs, but cppcheck reported accessMoved. Use if/else.
- The ABI tag test looked for "json_abi_bics", which misses when another
  tag comes first, as in json_abi_ldvcmp_bics; look for "_bics".
- readability-qualified-auto in the items() test.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
 2026-09-24 17:05:37 +02:00
Niels Lohmann 1705bfe914 🔖 set version to 3.12.0 (#4727) 
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
 2025-04-11 10:41:14 +02:00
Griffin Myers b36f4c477c Update natvis to reflect 3.11.3 and the current structure of basic_json (#4451) 
* Update natvis Jinja template to reflect the current structure of basic_json.

In 5a1a57510a the underlying structure of
basic_json was altered to move m_type and m_value under an m_data field.
This updates the nativ template to be consistent with this change.

* Generate nlohmann_json.natvis for 3.11.3 and latest basic_json structure.
 2024-09-05 20:28:24 +02:00
Niels Lohmann 349e4b310e Fix natvis XML (#3863) 
* 🐛 fix natvis XML

* 🐛 fix natvis XML
 2022-12-09 16:34:34 +01:00
Florian Albrechtskirchinger c0dae0f510 Add Python script for generating Natvis file and update file for 3.11.2 (#3697) 2022-08-12 08:24:32 +02:00
Axel Huebl a7567bc596 Remove EOL whitespaces in natvis 2018-11-02 10:42:48 +01:00
Matthias Möller 8e9a8792a9 moved natis to root dir 2017-11-30 13:26:45 +01:00