Commit Graph
26 Commits
Author SHA1 Message Date
Niels Lohmann d94a8d0a5a Merge remote-tracking branch 'origin/json-view/13-view-dump' into HEAD
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 17:20:28 +02:00
Niels Lohmann dfa17bd446 Merge remote-tracking branch 'origin/json-view/12-view-values' into HEAD
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 17:20:23 +02:00
Niels Lohmann 0b6a55ea6b Merge remote-tracking branch 'origin/json-view/11-view-access' into HEAD
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 17:20:19 +02:00
Niels Lohmann 5286c2843b Merge remote-tracking branch 'origin/json-view/10-view-document' into HEAD
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 17:20:14 +02:00
Niels Lohmann 3ba495ddf9 Merge remote-tracking branch 'origin/json-view/08-view-builder' into HEAD
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 17:20:09 +02:00
Niels Lohmann 2739c0b0af Merge remote-tracking branch 'origin/json-view/04-unicode-escapes' into HEAD
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 17:20:04 +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 38a2db260c Remove dead metaprogramming and duplicated code in traits and pointers (#5728)
* Remove unused is_sax and is_detected_convertible

detail::is_sax had no user: the parser and the binary reader only use
is_sax_static_asserts, so is_sax was a second, unchecked copy of the
SAX event list. is_sax_static_asserts asserted boolean(bool) twice in
a row, and detail::is_detected_convertible was never used anywhere.

Remove all three and include <cstddef> for size_t instead of <cstdint>.
Only names in nlohmann::detail are removed; behavior, public API and ABI
are unchanged. The diagnostics for an incomplete SAX handler are the
same, apart from the duplicated boolean() message.

Part of #5708

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

* Replace meta/logic.hpp with a disjunction trait

meta/logic.hpp added a second set of type-level boolean helpers
(cxpr_and, cxpr_or, cxpr_not, ...) next to the existing conjunction
and negation in type_traits.hpp. It was used only by one static_assert
in from_json_tuple_impl, two of its templates were never used, and it
was the only header without the license banner and relied on
transitive includes for <type_traits>.

Add the missing disjunction next to conjunction and negation, use the
three in the static_assert, and delete logic.hpp together with its
BUILD.bazel entry. same_sign now uses disjunction as well, which
resolves the 2022 TODO waiting for such a trait.

The static_assert accepts and rejects the same types as before. Only
names in nlohmann::detail change; behavior, public API and ABI are
unchanged.

Part of #5708

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

* Remove unused would_call_std_* from NLOHMANN_CAN_CALL_STD_FUNC_IMPL

Besides detail::result_of_begin/end, which is_range and iterator_t use,
the macro defined a namespace detail2 with a tag type, a catch-all
overload and would_call_std_begin/end, plus would_call_std_begin/end
structs directly in namespace nlohmann. Nothing has used them since
they were added in #3020.

Reduce the macro to its detail part. Without the trailing struct the
';' after the two invocations would be an empty declaration that
-Wextra-semi flags, so drop it. macro_scope.hpp included
meta/detected.hpp only for this macro; all users of detected.hpp
include it (or type_traits.hpp) themselves, so remove the include.

Behavior and ABI are unchanged. The undocumented, untested and unused
names nlohmann::would_call_std_begin, nlohmann::would_call_std_end and
namespace nlohmann::detail2 are no longer declared.

Part of #5708

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

* Simplify is_ordered_map to reuse has_capacity

is_ordered_map re-detected capacity() with a C++03 sizeof/vararg
trick right after has_capacity did the same detection through
is_detected. For ordered_map, the old trick took the address of
std::vector::capacity, which [namespace.std]/6 makes unspecified.
Reuse has_capacity instead, which removes the unspecified-behavior
pointer-to-std-member and two NOLINT suppressions.

Part of #5708

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

* Remove duplicate const overload of json_pointer::get_checked

The const and non-const get_checked() overloads had byte-identical
50-line bodies, differing only in the signature. The remaining
template deduces a const-qualified BasicJsonType for const callers,
so at(), the out_of_range::create() calls and the bounds check all
still work.

Part of #5708

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

* Fix tautological clause in iter_impl's iterator category assertion

The static_assert meant to check the LegacyBidirectionalIterator
named requirement had a first clause comparing
std::bidirectional_iterator_tag to itself, which is always true and
checks nothing; only array_t::iterator was actually being checked,
despite the message claiming object iterators were checked too.
Drop the tautological clause, reword the message to describe what
is actually checked, and note that object_t may use a forward-only
iterator as long as reverse iteration and operator-- are unused.
The check is intentionally not extended to object_t::iterator, since
that would reject object types with forward-only iterators that
compile and work correctly today.

Part of #5708

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

* Fix misplaced and stale comments in JSON_HAS_RANGES and conversions

The JSON_HAS_RANGES feature-detection block had its libc++ comment
sitting above the clang+libstdc++ branch it does not describe,
leaving the libc++ branch uncommented and the clang+libstdc++ branch
without its own rationale. Move each comment to sit under its own
branch, and give the clang+libstdc++ branch (added in issue 5161) its
own one-line reason referencing that issue instead of reusing the
libc++ branch's comment. Also fix a duplicated-word typo ("in large
in large cpp files") in from_json.hpp, drop two unanswered 2017
design questions left as comments in type_traits.hpp and
from_json.hpp that no longer reflect open questions, and correct
NLOHMANN_JSON_SERIALIZE_ENUM_STRICT's @since tag from 3.12.0 to
3.13.0, the release it was actually introduced in.

Part of #5708

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

* Support any-rank C arrays in from_json, not just rank 1-4

from_json() for C arrays had four hand-unrolled overloads (rank 1-4,
added incrementally in #4262), each with its own nested loops. to_json()
already handles any rank recursively, so a rank-5+ C array could be
serialized but not read back with get_to()/get<>().

Replace the four overloads with one from_json() SFINAE-constrained on
get<remove_all_extents<T>::type>() existing, forwarding to a pair of
mutually recursive from_json_c_array_element() helpers: one assigns a
non-array element via get<T>(), the other loops over a array element and
recurses one dimension at a time. Each dimension still goes through at(),
so type_error.304/out_of_range.401 stay unchanged; ranks 1-4 keep their
existing behavior and semantics.

Adds rank-5 round-trip and mismatched-shape tests to unit-conversions.cpp.

Public API: additive only (rank 5+ C arrays become readable).

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

#5708 item 1

* Move templated_json_throw into nlohmann::detail

templated_json_throw() was defined in macro_scope.hpp, which is included
outside NLOHMANN_JSON_NAMESPACE_BEGIN, so the helper leaked into the
global namespace as ::templated_json_throw with no ABI tag. Unqualified
lookup in NLOHMANN_JSON_SERIALIZE_ENUM_STRICT could then bind to a
same-named function declared in the user's own namespace instead, which
fails to compile with Clang ("does not name a template").

Move the helper next to the exception classes in exceptions.hpp, inside
nlohmann::detail, and call it qualified as
::nlohmann::detail::templated_json_throw<...>(...) from both macro
expansion sites. Rewrite the doc comment to give the real reason for the
helper (JSON_THROW may expand to code that discards its argument, e.g.
when exceptions are disabled) and fix the "supress" typo.

templated_json_throw was never released (added by #5151 after v3.12.0),
so it can be moved freely.

Adds a regression test that expands NLOHMANN_JSON_SERIALIZE_ENUM_STRICT
inside a namespace declaring its own templated_json_throw.

Public API: no change (::templated_json_throw was an unreleased,
unintentional global-namespace leak with no callers relying on its
location).

Overlaps #5698, which rewrites the same two macro call lines; the
overlapping hunks are small and should be trivial to reconcile on
rebase.

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

#5708 item 2

* Factor the repeated JSON_HAS_RANGES/MinGW guard into one macro

The std::ranges view conversion (excluded on MinGW because of its
incomplete C++20 ranges support, #4916) was gated by the same
#if JSON_HAS_RANGES && !defined(__MINGW32__) condition at seven
independent sites in to_json.hpp and type_traits.hpp, with the MinGW
rationale duplicated in two of them and missing from the rest. Since the
sites come in matching pairs (one enables is_compatible_range_view and a
view-based overload, the other adds the exclusion to the
plain-array-type overload), a drift between any pair would produce an
ambiguous or missing overload on exactly one platform.

Add JSON_HAS_RANGE_VIEW_CONVERSION next to JSON_HAS_RANGES in
macro_scope.hpp, combining both conditions with the #4916 reasoning in
one place, #undef it in macro_unscope.hpp, and use it at all seven
sites. This does not fold the MinGW check into JSON_HAS_RANGES itself:
JSON_HAS_RANGES is user-overridable and also gates the
enable_borrowed_range specialization in iteration_proxy.hpp, which is
not excluded on MinGW.

No behavior or public API change: JSON_HAS_RANGE_VIEW_CONVERSION expands
to exactly the condition that was previously written out at each site.

Overlaps #5585, #5600 and #3575, which touch the same to_json.hpp and
type_traits.hpp lines; the change here is a mechanical
search-and-replace of the guard condition and should rebase cleanly.

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

#5708 item 11

* De-duplicate from_json.hpp's map and array-fallback bodies

Several from_json() overload pairs in from_json.hpp were copies of each
other, so a fix has to be applied twice (as #5681 already does):

- from_json(..., std::map&) and from_json(..., std::unordered_map&) for
  non-string keys had identical 16-line bodies: array check, m.clear(),
  pair check loop, m.emplace(...). Route both through a new
  from_json_pair_array_to_map(j, m) helper.
- The from_json_array_impl priority_tag<1> and priority_tag<0> fallbacks
  ran the same std::transform/std::inserter loop, differing only in
  ret.reserve(j.size()). Merge them into one body and, modeled on the
  existing from_json_object_reserve, add a from_json_array_reserve pair
  so the reserve() call is only made for ConstructibleArrayType that
  support it.

Error ids (type_error.302), messages, diagnostic paths ((at(0)/at(1))
and behavior for types with/without reserve() are unchanged; only the
duplication is removed.

Public API: no change.

Overlaps #5681, which changes the "&j" to "&p" line in both map bodies;
the shared helper here should make that a one-line change instead of two
on rebase.

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

#5708 item 5

* Unify json_pointer's three array-index parsers

array_index(), contains() and get_checked_or_null() each re-implemented
the RFC 6901 array-index rules and the size_type range check: array_index()
does the canonical parse and throws; contains() (which must not throw,
#5395) re-validates every digit by hand and runs its own strtoull/ERANGE
check before calling array_index() anyway, parsing every array token
twice; get_checked_or_null() wraps array_index() in JSON_TRY/
JSON_INTERNAL_CATCH (detail::out_of_range&) to turn an unrepresentable
index into "not found".

Add a single private, noexcept parse_array_index(s, idx) returning an
array_index_status (ok / leading_zero / not_a_number / unresolved /
exceeds_size_type). array_index() becomes a thin wrapper mapping each
status to the existing parse_error.106/109 or out_of_range.404/410;
contains() and get_checked_or_null() switch on the status directly. This
removes contains()'s digit-validation loop and its second strtoull call,
and get_checked_or_null()'s JSON_TRY/JSON_INTERNAL_CATCH.

Bugfix as a consequence: get_checked_or_null()'s JSON_TRY/
JSON_INTERNAL_CATCH was dead code under JSON_NOEXCEPTION (JSON_TRY
expands to "if(true)" and the catch to "if(false)", so JSON_THROW's
std::abort() ran unconditionally), meaning value() and contains() would
abort instead of returning the default/false for an out-of-range-sized
or oversized array index when exceptions are disabled (#5672). Switching
on parse_array_index()'s return value instead of relying on an actual
throw/catch fixes this: get_checked_or_null() now returns nullptr for
array_index_status::unresolved/exceeds_size_type in every build
configuration, and still calls JSON_THROW (aborting under
JSON_NOEXCEPTION, as before) only for a malformed index
(leading_zero/not_a_number), matching its documented @throw list.

All existing error ids, messages and diagnostic paths are unchanged; a
few reference tokens that used to fail contains()'s manual per-character
validation (e.g. "1a") now fail via array_index_status::unresolved
instead, with no observable difference since contains() only returns
bool.

Adds regression tests to unit-element_access2.cpp's "access on array
type" section covering value() with an index that exceeds size_type and
one with a trailing non-digit, both of which must yield the default
value rather than abort/throw.

Public API: no change.

Overlaps #5700, #5614 and #5692, which touch the contains() and
get_checked_or_null() array hunks; this change replaces those hunks with
calls into the new shared parser, so a rebase will need to re-apply
their token-handling changes (e.g. the empty-token case) on top of the
switch statements here.

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

#5708 item 4

* Regenerate single_include after merging develop

The merge commit kept develop's single_include/nlohmann/json.hpp because
make amalgamate saw it as up to date.

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

* Address review: switch in array_index, drop redundant inline

- json_pointer::array_index() dispatches on array_index_status with a
  switch, matching the other parse_array_index() caller
- drop `inline` from the function templates this PR adds or moves in
  from_json.hpp
- reword a comment that described the change rather than the code

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 11:50:42 +02:00
Niels Lohmann e842f3a68f Add comparisons to json_view
basic_json_view gains operator== and operator!= with other views and with
basic_json values. Two views are equal if the values parse() would
produce for them are equal by basic_json's operator==: numbers compare by
value across their types, and objects by their members, with duplicate
keys resolved as parse() resolves them (the last value, at the position of
the first key). Objects are compared in member order if the object type
keeps an order (ordered_json), by key otherwise, as basic_json does.
Discarded views compare as discarded basic_json values do, which follows
JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON. Nothing is materialized except
single numbers, and the walk is iterative.

Tests compare the results for pairs of 1,200 generated documents (also
written differently: sorted keys, canonical numbers) with those of
basic_json, for json and ordered_json, plus numbers, duplicate keys,
member order, discarded values, and 100,000 levels of nesting.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-30 21:01:47 +02:00
Niels Lohmann 83d72fd7a7 Add dump() to json_view
basic_json_view::dump(indent, indent_char, ensure_ascii, number_format)
writes the text of a value as ordered_json::parse(text).dump() writes it
for the same arguments: members in document order (all of them, should a
key occur more than once), strings escaped by the same rules and with the
library's scanning kernels, floats with the library's conversion, and
integers copied from the source, where they are canonical except "-0".
With number_format::source, numbers are copied as they appear in the
source ("1.50", "1E2", "-0", all digits of long integers). operator<<
takes the indentation from the stream width, as for basic_json.

The writer (detail/view/serializer.hpp) writes through a raw pointer into
a string sized from the source extent of the value, and walks the index
iteratively, so the nesting depth is limited by memory only.

Tests compare the output of 2,000 generated documents with
ordered_json::dump() for several indentations and ensure_ascii, strings
with every kind of escape, numbers (5,000 random doubles, float as
number_float_t), duplicate keys, 100,000 levels of nesting, and streams.
ViewDump joins the benchmarks.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-30 21:01:42 +02:00
Niels Lohmann 0650a48659 Add values and JSON pointers to json_view
basic_json_view gains get<T>(), get_to(), value() with keys and JSON
pointers, and operator[], at(), and contains() with JSON pointers, plus
two functions basic_json has no counterpart for:

- get_string(): the string without a copy (a string_view into the source,
  or into the decoded strings for strings with escapes)
- number_token(): the text of a number as it appears in the source

get<T>() converts arithmetic types, strings (also string_view_t),
std::nullptr_t, std::vector, maps with string keys, and views directly;
floats are converted from the digit layout recorded by the parser with the
library's conversion chain, so the values are bit-identical to parse().
Other types, including user types with from_json(), go through
materialize().

The exceptions are those of basic_json, message included. Where const
basic_json has undefined behavior (a missing key or an index out of range
with operator[] and a JSON pointer), the result is a discarded view;
value() returns the default wherever basic_json catches out_of_range, and
contains() never throws. Array indices of JSON pointers follow
json_pointer's rules (parse_error.106/109, out_of_range.404/410).

Tests compare the conversions of 2,000 generated documents, 20,000 float
tokens (double and float, bit for bit), and every JSON pointer of 1,000
documents with basic_json, and the exceptions for malformed pointers.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-30 21:01:36 +02:00
Niels Lohmann 7dae258350 Add element access, lookup, and iteration to json_view
basic_json_view gains the read-only access functions of basic_json:
operator[] and at() with keys and indices, front(), back(), find(),
contains(), count(), begin()/end(), items() (with structured bindings from
C++17 on), and type_name(). They throw the exceptions (ids and messages)
that the const functions of basic_json throw; where basic_json has
undefined behavior (operator[] with a missing key or an index out of
range, front()/back() of an empty container), the view returns a
discarded view or throws invalid_iterator.214.

Objects are iterated in document order, and all members are visited. With
duplicate keys, lookups find the first member, so that a lookup can stop
at the first match; parse() keeps the last value. Keys of up to 16 bytes
are compared with two overlapping loads instead of memcmp, and most keys
are rejected by their length alone, from the index.

The iterators and items live in detail/view/iterator.hpp, the lookups in
detail/view/lookup.hpp. Tests compare every element and member of 2,000
generated documents with ordered_json, keys of every length around the
load sizes, the exceptions against const basic_json, and the iterators.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-30 21:01:32 +02:00
Niels Lohmann 08e677ad61 Build, install, and check json_view.hpp
The new single header goes through the same checks and install steps as
json.hpp and json_fwd.hpp:

- cmake/ci.cmake: ci_test_amalgamation regenerates, formats, and compares
  json_view.hpp as well
- check_amalgamation.yml: the pull request check does the same; it runs
  develop's tools, so it needs config_json_view.json on develop first
- meson.build: installs single_include/nlohmann/json_view.hpp
- gen_bazel_build_file.cmake, BUILD.bazel: json_view.hpp joins the
  single-header target; the glob of the other target already covers the
  new headers
- labeler.yml: an "aspect: json_view" label for the header, its
  detail/view headers, tests, and documentation

The CMake install rules for include/ and single_include/, the REUSE
catch-all, and Package.swift cover the new files without changes.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-30 20:58:15 +02:00
Niels Lohmann cf352d4ef5 Add json_document and json_view: parse, accept, types, materialize
The public classes of the zero-copy view (#5295), in the new header
<nlohmann/json_view.hpp>:

- basic_json_document<BasicJsonType>: parse (borrowing contiguous byte
  inputs, owning rvalue strings, streams, and other inputs), parse_copy,
  accept, read, root, is_discarded, source, owns_source, node_count,
  memory_usage, shrink_to_fit
- basic_json_view<BasicJsonType>: type and the is_* queries, size, empty,
  materialize (the value parse() would produce, built by the same SAX
  handler), source_offset
- the aliases json_document, json_view, ordered_json_document, and
  ordered_json_view

A parse error throws the exception basic_json::parse would throw for the
same input: the library parser is run on the failing input, so messages,
positions, and exception ids are the same. Inputs of 4 GiB or more are
rejected with out_of_range.416.

The single header single_include/nlohmann/json_view.hpp keeps including
json.hpp; make amalgamate, check-amalgamation, include.zip, and release
handle it.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-30 20:57:43 +02:00
Niels Lohmann ad82821c89 Add the one-pass parser of json_view (internal)
The builder parses JSON text in one pass into the node index: strings and
numbers stay in the source (escaped strings are decoded into an arena),
integers are converted while their digits are in cache, and floats keep
their digit layout for a later conversion. It accepts exactly what
json::parse accepts, for every combination of comments and trailing commas,
with and without a terminating NUL, and with JSON_STRICT_NUL_HANDLING.

Parse state lives in a local cursor whose address never escapes, so that it
stays in registers; out-of-line helpers (errors, regrowth, escapes,
comments) are members of the builder and get the positions they need. The
value dispatch is expanded once for array elements and once for member
values. Literals are compared with memcmp and words read in a fixed byte
order, so nothing depends on the platform's byte order. Error messages come
with the public classes.

Tests (unit-json_view_builder.cpp): accept/reject and values against
json::parse for handwritten, generated, and damaged documents under all
option combinations, from std::string and from exact-size buffers (no read
past the input under AddressSanitizer), deep nesting up to 100,000 levels,
NUL/BOM/whitespace cases, and the test-suite files.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-30 20:19:13 +02:00
Niels Lohmann 1bf0b1b6c2 Add the node index and scanning primitives of json_view (internal)
Internal parts of the zero-copy view (#5295), under detail/view and not
included by json.hpp, so that users of json.hpp compile nothing of it:

- macro_scope.hpp/macro_unscope.hpp: the few macros the view needs, under
  its own prefix (json.hpp undefines its own at its end); the throw macro
  honors JSON_NOEXCEPTION and JSON_THROW_USER like JSON_THROW
- string_ref.hpp: std::string_view from C++17 on, else a small stand-in
- node.hpp: the 16-byte node of the index; its kinds are value_t values
  (checked by a static_assert)
- document_data.hpp: the storage of a parsed document (node array, decode
  arena, owned input)
- scan.hpp: string and digit scanning with unrolled checks at fixed offsets
  (after yyjson) and the library's SWAR and UTF-8 checks, independent of the
  byte order

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-30 20:19:13 +02:00
Niels Lohmann b88e5f9107 Keep the behavior-changing configuration readable after json.hpp
json.hpp undefines JSON_STRICT_NUL_HANDLING and
JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON at its end. Code that builds on
the library after it, such as the planned json_view.hpp, reads them from
detail::abi_config instead. The constants live in the ABI namespace, which
already encodes both settings, so they always match the basic_json in use.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-30 20:19:13 +02:00
Niels Lohmann 6fc0d501f3 Move the user-defined string literals to <nlohmann/json_literals.hpp> and add JSON_NO_AUTOMATIC_UDLS (#5610)
* Add JSON_NO_UDLS to leave out the user-defined string literals

The bodies of operator""_json and operator""_json_pointer call the
parser, so every translation unit including the library instantiates it,
even if it never parses anything. Defining JSON_NO_UDLS leaves the
literals out entirely, which saves 15-35% compile time for such
translation units (#5294). Nothing changes if the macro is not defined.

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

* Mention JSON_NO_UDLS in the list of exported module symbols

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

* Move the user-defined string literals to <nlohmann/json_literals.hpp>

Following the review in #5294, the literals now live in their own header
instead of being removed entirely: <nlohmann/json.hpp> includes it at the
end unless JSON_NO_AUTOMATIC_UDLS (renamed from JSON_NO_UDLS) is defined,
so a project can opt out globally and include the header only where the
literals are used.

The header only uses public and standard macros, because the library's
internal macros are undefined at the end of json.hpp and the amalgamation
inlines macro_scope.hpp only once. For the same reason, the library no
longer defines and undefines JSON_USE_GLOBAL_UDLS, so a user's definition
is still visible to the header. The single-header copy is identical to
the multi-header one, as it only includes <nlohmann/json.hpp>. The module
always exports the literals.

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

* Fix CI: include cycle, GCC 4.8 literal operator spacing, and global UDLs off in the JSON_NO_AUTOMATIC_UDLS test

- Suppress clang-tidy misc-header-include-cycle on the intentional mutual
  include of json.hpp and json_literals.hpp.
- Use operator"" _json with a space for GCC 4.8 in the test's detection
  aliases, as the header does.
- Only test the global literal operators when JSON_USE_GLOBAL_UDLS is on.

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

* Declare the literal operators through a local macro

The GCC 4.8 spacing condition was repeated for both operator definitions
and the global using-declarations. NLOHMANN_JSON_LITERAL_OPERATOR(suffix)
now selects operator""##suffix or operator"" suffix in one place and is
undefined at the end of json_literals.hpp.

Suggested by gregmarr in review.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-30 20:08:17 +02:00
Niels Lohmann d268eaa693 Convert floats with Eisel-Lemire when std::from_chars is unavailable (#5617)
* Convert floats with Eisel-Lemire when std::from_chars is unavailable

Float tokens that Clinger's fast path cannot convert (e.g. the 17-digit
coordinates of canada.json) went to strtod unless std::from_chars was
available. It is not used in C++11/14, and not with libc++, which does not
define __cpp_lib_to_chars. The Eisel-Lemire algorithm (after fast_float's
compute_float) now converts them with integer arithmetic, correctly rounded
for any token with at most 19 significant digits. Longer tokens are
truncated; the result is used if w and w + 1 round alike, else strtod
decides as before. Overflow still yields infinity (out_of_range.406).

The table of powers of five (fast_float's) lives in pow5_table.hpp; a unit
test recomputes every entry with big-integer arithmetic. Further tests:
known values generated with Python (whose float() is correctly rounded),
200,000 round trips through to_chars, and the 128-bit multiplication and
leading-zero count against big-integer references (both with and without a
128-bit type). Checked against strtod on 6.5 million tokens, among them
60,000 exact halfway cases: no difference.

json::parse on canada.json: -8.6% (C++11), -7.6% (C++17, Apple clang);
other files unchanged. Compile time of a TU including json.hpp: +0.7%.

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

* Fix CI: unused parse result and find() == npos in the Eisel-Lemire tests

GCC (-Werror=unused-result) rejected CHECK_THROWS_WITH_AS(json::parse(...))
because parse() is [[nodiscard]]; assign the result to a dummy json as the
other tests do. clang-tidy flagged longer.find('.') == npos with
abseil-string-find-str-contains; store the position in a variable first.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-30 20:06:26 +02:00
Jeremy Nimmer 6c8ea0a6d1 Remove Bazel alwayslink=True (#5376)
This should have no effect for header only libraries as mentioned.

It was previously removed in e509007d but then accidentally added
again in 26cfec34.

Signed-off-by: Jeremy Nimmer <jeremy.nimmer@tri.global>
2026-09-25 08:46:19 +02:00
Niels Lohmann 7c90ec2323 Hash deeply nested values without recursing per nesting level (#5546)
* Hash deeply nested values without recursing per nesting level

std::hash<basic_json> hashed an array or object by hashing each element,
which called detail::hash again once per nesting level. A value nested
deeply enough - 50,000 levels of objects on an 8 MiB stack - exhausted
the call stack and terminated the process. parse() accepts such values
without complaint, since the parser is iterative, and a parsed value is
hashed wherever it is used as a key in an unordered container.

Bound the descent the same way dump() does: detail::hash takes the
nesting level, and once hash_depth_limit() (128) levels have been entered,
hash_iteratively() hashes what is left on an explicit stack. It combines
the seeds in exactly the same order, so hash values are unchanged. A value
nested less deeply than the bound is hashed by the same code as before,
without allocating, and is as fast as before.

Tests check that every depth up to twice the bound hashes exactly like
the recursive definition of the hash, and that values nested 100,000
levels deep hash without crashing.

Fixes #5545 for std::hash.

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

* Declare hash_frame's constructor noexcept

GCC's -Wnoexcept (an error in CI) flags the emplace_back() into the
hash stack under C++26: the constructor cannot throw, since cbegin() is
noexcept, but it did not say so. dump_frame's constructor is noexcept
for the same reason.

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

* Share one recursion depth limit, and copy the hash frame out of the stack

dump() and hash() each defined their own limit on how many nesting levels
they recurse into, and the operations still to come would have added more,
free to diverge over time. They now all use detail::recursion_depth_limit(),
in a header of its own; serializer::dump_depth_limit() and
hash_depth_limit() are gone.

hash_iteratively() now copies the frame it works on out of the stack and
changes the frame only through stack.back(), so nothing can refer into
the stack after entering an element has grown it.

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

* Parenthesize multiplications in the hash test for clang-tidy

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-24 17:12:02 +02:00
Niels Lohmann 305ca7dadd Add missing headers to BUILD.bazel and check it in CI (#5554)
* Add missing headers to BUILD.bazel and make its generator reproduce it

The "json" cc_library did not list three headers that the library
includes:

- detail/meta/logic.hpp (added in #5016, included by from_json.hpp)
- detail/input/number_parse.hpp (added in #5283, included by lexer.hpp)
- detail/input/string_scan.hpp (added in #5283, included by lexer.hpp
  and serializer.hpp)

Bazel's sandbox only exposes declared headers, so any target depending
on @nlohmann_json//:json and including <nlohmann/json.hpp> failed with
"'nlohmann/detail/meta/logic.hpp' file not found".

The file could not simply be regenerated, because the generator behind
"make BUILD.bazel" was stale: it wrote only the "json" cc_library and
dropped the load() statements, the license block, and the
"singleheader-json" target that were added by hand in #4584. The
generator now emits the complete file, so its output differs from the
previous BUILD.bazel only by the three headers. It also resolves the
glob against the project root instead of the working directory and
sorts the list explicitly.

"make BUILD.bazel" is now phony: in a fresh checkout, BUILD.bazel is
not older than the headers, so make considered it up to date, and a
removed header would never trigger a rebuild. "make check-amalgamation"
also checks that BUILD.bazel is up to date.

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

* Check in CI that BUILD.bazel is up to date

The "Check amalgamation" workflow now also regenerates BUILD.bazel, so a
pull request that adds, renames, or removes a header without updating
the Bazel header list fails, and the attached amalgamation.patch
contains the fix. The failure comment and the contribution guidelines
mention the new check, and the comment now links to the existing
"Amalgamate the source code" section instead of the "Files to change"
anchor that was removed in #4560.

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

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-24 17:07:21 +02:00
Niels Lohmann 26cfec34be Clean up and document project files (#4560) 2025-01-17 06:53:35 +01:00
Vertexwahn 0cb1241d5e Improve Bazel support: Switch to Bzlmod (#4584)
* Improve Bazel support: Switch to Bzlmod

Signed-off-by: Vertexwahn <julian.amann@tum.de>

* Update documentation

Signed-off-by: Vertexwahn <julian.amann@tum.de>

* Fix spelling

Signed-off-by: Vertexwahn <julian.amann@tum.de>

* Fix snippet filename error

Signed-off-by: Vertexwahn <julian.amann@tum.de>

---------

Signed-off-by: Vertexwahn <julian.amann@tum.de>
2025-01-07 18:47:51 +01:00
Marcel e509007df2 Remove alwayslink=True Bazel flag (#4396) 2024-11-16 23:13:11 +01:00
Vertexwahn 2d1f9b6a7d Add Bazel build support (#3709) 2022-09-18 08:15:12 +02:00