* Review and extend the documentation, and check it in CI
A review of all documentation pages found factual errors, dead links,
missing cross-references, and gaps in examples. This fixes them and adds
checks so the same problems are caught automatically.
Fixes:
- wrong signatures and version histories (operator!= C++20 member,
binary() subtype type, get<PointerType>(), JSON_NO_THREAD_LOCAL, ...)
- stale descriptions (number parsing since #5283, UBJSON table, SAX
example that no longer compiled, tsl::ordered_map advice)
- dead internal and external links; repology.org badges (the domain is
suspended) replaced by badges that query the registries directly
- deprecation notes link the migration guide; the guide itself fixed
Additions:
- "See also" sections, cross-references, 25 runnable examples, 12
Mermaid diagrams, new API pages for json_pointer::operator<=> and
byte_container_with_subtype::operator==/!=
- landing page, guides for untrusted input and performance
- "unreleased" badge after versions newer than the latest release
Checks:
- strict documentation build (broken links/anchors fail it); CI and
the publish workflow fetch the full history the build needs
- weekly external link check, Mermaid syntax check in CI
- check_structure.py: example titles, heading levels, alt texts,
header links, docset index coverage; its unused-example check works
again
- all examples produce the same output on every platform
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Keep the customer links that could not be fixed
A dead link on the customers page is still the evidence of where the
use of the library was documented. Keep the original URLs of the entries
without a working replacement (Marne, Cisco Webex Desk Camera, Philips
Hue, CyberArk) and exclude exactly these URLs from the link check.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Correct the duplicate-key recipe's claim about SAX positions
The SAX interface's key() receives no position either; only parse_error()
does. Also note that the recipe does not report the path to the repeated
key (see discussion #5085).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Say the library is available as a single header and mention json_fwd.hpp
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Correct documentation errors found while hunting for bugs
- patch/patch_inplace: list the JSON pointer errors parse_error.106-109
and out_of_range.402/404, and quote the actual parse_error.105 message.
- unflatten: list parse_error.106/107/108 and out_of_range.404.
- to_bson: list out_of_range.415 (binary subtype above 255) and note
that 412 and 415 are new in 3.13.0.
- to_string: state that string_t must be convertible to std::string, also
in the StringType requirements table.
- JSON Lines: a `while (input >> j)` loop also throws after the last value
for concatenated JSON values; show a loop that works for both.
- BON8: a string gets 0xFF only if nothing follows it in the message; a
string at the end of an array or object is ended by 0xFE.
- custom_string_type.hpp: add operator+=(char), which the "Always
required" list asks for (json_pointer::to_string, flatten, unflatten,
and diff did not compile), and an ADL int_to_string for diff and items.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Cache the release headers with functools.lru_cache
Codacy (Pylint) flagged the mutable default argument that header() used
as its cache. functools.lru_cache keeps the same memoization without it.
The script's output is unchanged.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Add JSON_DISABLE_TUPLE_REFERENCE_CONVERSION to fix std::tuple conversions
basic_json can be constructed from std::tuple<json&>, which it turns into
a one-element array. Because of this, std::tuple picks its converting
constructor that converts the whole source tuple instead of the
element-wise one. As a result, std::tuple<const json&> built from
std::forward_as_tuple(j) binds to a temporary (a compile error with libc++,
a dangling reference with other standard libraries), and std::tuple<json>
built the same way holds [j] instead of a copy of j.
The new opt-in macro JSON_DISABLE_TUPLE_REFERENCE_CONVERSION (CMake option
JSON_DisableTupleReferenceConversion) removes the conversion from a
one-element tuple holding a reference to the same basic_json type, so
std::tuple converts element-wise. It is off by default, so existing
behavior is unchanged. It does not change any function body and therefore
is not part of the ABI tag.
Fixes#2226
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Convert one-element tuples to arrays on every compiler
to_json for std::tuple assigns a braced list, j = { std::get<Idx>(t)... }.
With a single element that is itself a basic_json, Apple clang 15 and 16
treat j = {x} as a copy of x, so std::tuple<json>{true} became true
instead of [true]. The macOS jobs (Xcode 15.1, 16.1) failed the new
checks in unit-disable-tuple-reference-conversion and unit-regression2.
The one-element overload that already handles
JSON_BRACE_INIT_COPY_SEMANTICS builds the array (or object, for a
[string, value] element) explicitly, the same way the initializer-list
constructor does. Use it unconditionally. The output is unchanged on
compilers that already wrapped the element.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Skip json reference tuple tests on clang < 4 and GCC < 5
ci_test_compilers_gcc_old (4.8) and ci_test_compilers_clang (3.4) could
not compile the new tuple tests. Creating a std::tuple of basic_json
references, e.g. std::forward_as_tuple(j), makes these compilers
instantiate basic_json's conversion operator for libstdc++'s internal
tuple bases, which fails hard. This happens with and without
JSON_DISABLE_TUPLE_REFERENCE_CONVERSION, so it is a limitation of these
compilers, not of the new option.
Tested with the CI images: clang 3.4 to 3.9 and GCC 4.8 and 4.9 fail,
clang 4, 5, and 6 and GCC 5 and 6 compile all cases. Skip only the
checks that create such tuples; the is_constructible checks still run.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
basic_json(first, last) treated value_t::binary like the structured
types (array, object) in the range check, so it always copied the
whole binary value regardless of the iterators, even for an empty
range such as (b.end(), b.end()). The other primitive types (number,
boolean, string) already reject such a range with
invalid_iterator.204, and erase(first, last) already does the same
for binary values, so this made the constructor inconsistent with
both. Move case value_t::binary into the group of checked primitive
types.
Also update the two matching passages in basic_json.md that describe
overload 7, and add a version-history note.
Fixes#5670.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* 📝 Fix documentation gaps found in a full GitHub Discussions review
Reviewed all 1008 GitHub Discussions (2020-2026) for recurring questions
that better or more visible documentation would have avoided. Adds/expands
documentation for ~26 distinct gaps, including:
- New "Debugging" page collecting natvis, GDB pretty printer, LLDB status,
and JSON_DIAGNOSTICS pointers (previously scattered/undiscoverable)
- Thread-safety and schema-validation FAQ entries
- StringType's char-based requirement (no wstring/u16string/u32string)
- Brace-initialization-yields-arrays warning directly on the constructor
reference page (previously only in the FAQ, missed by users reading
the constructor docs)
- std::any exclusion from get<T>(), with a manual-dispatch example
- Non-string-keyed std::map serializing as an array of pairs
- ordered_json compatibility with NLOHMANN_DEFINE_TYPE_* macros
(already worked, was undocumented)
- std::array truncation on size-mismatched conversion (no exception)
- static_cast vs. get<std::optional<T>>() divergence
- Recipe for omitting a std::optional field instead of emitting null
- No built-in nesting-depth limit during parsing + a callback-based
workaround recipe
- Recipe for streaming a large homogeneous array via parser callbacks
- operator>> stream-position semantics for concatenated JSON values
- JSON Pointer array-vs-object creation rule for non-existing paths
- CMake target name (nlohmann_json_modules) needed to link C++20 modules
- ESP-IDF/PlatformIO: no official package, link to a community fork
- get(key, default) as the Python dict.get() equivalent
- reserve() recipe for pre-allocating array capacity
- JSONC as an alias for the existing ignore_comments/ignore_trailing_commas
combination (distinct from the unsupported JSON5)
- items() dereferenced-element type: decltype() idiom + detail-namespace
stability caveat
- Various macro/type-conversion limitations (MSGPACK_DEFINE_ARRAY
equivalent, char-array round-tripping, ADL serializer macro gap)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* 🎨 fix format
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
When converting objects or strings between different basic_json specializations,
the target's object_t::key_type or string_t must be directly constructible from
the source's corresponding type. If this requirement is not met, the conversion
silently falls back to the array-conversion path, producing incorrect results.
This documents the limitation and provides references to issue #3425, which tracks
this behavior. The comment in unit-alt-string.cpp is clarified to reference the
known limitation with a link to the issue, and suggests the parse() workaround.
Fixes#3425 (documentation; full fix deferred pending type-trait redesign)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Niels Lohmann
