* Support zero-member types in NLOHMANN_DEFINE_TYPE_* macros (#4041)
NLOHMANN_DEFINE_TYPE_INTRUSIVE(Type) and its 11 sibling macros produced
broken code for types with no members to serialize. Invoking a variadic
macro so __VA_ARGS__ is empty is only standard-conforming since C++20,
so a plain __VA_OPT__ fix (as tried in #5142) breaks every pre-C++20
build under -pedantic. Instead, make all 12 macros purely variadic and
dispatch on argument count using a sentinel-padded extension of the
existing NLOHMANN_JSON_GET_MACRO idiom, giving full C++11-C++26 support
with no feature-test gate.
Verified against real GCC 16 and Clang at -std=c++11/14/17/20 with
-pedantic -Werror -Wvariadic-macros: zero regressions in the existing
unit-udt_macro.cpp suite plus 12 new zero-member test cases.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix CI failures in zero-member NLOHMANN_DEFINE_TYPE_* macros
Three issues surfaced on PR #5272's real CI that weren't caught by
local testing against a narrower flag set:
- GCC -Werror=noexcept: the four truly-empty from_json bodies (plain
INTRUSIVE/NON_INTRUSIVE, with and without _WITH_DEFAULT) provably
never throw but weren't declared noexcept; mark them noexcept
explicitly. to_json and the derived-type from_json overloads are
left alone since they genuinely can throw (object assignment /
delegating to the base class's from_json).
- clang-tidy bugprone-macro-parentheses: false positive on the same
8 zero-member bodies (Type/BaseType used purely as declarator
types); suppressed with NOLINTNEXTLINE comments in the same style
already used elsewhere in this file (see NLOHMANN_JSON_SERIALIZE_ENUM).
- MSVC's traditional preprocessor doesn't fully expand
NLOHMANN_JSON_CAT(prefix, NLOHMANN_JSON_TYPE_TAG(...))(...) in one
pass, which broke a pre-existing one-member usage in
unit-regression2.cpp with syntax errors. Wrap all 12 public
dispatcher macros in an extra outer NLOHMANN_JSON_EXPAND(...),
matching the pattern NLOHMANN_JSON_PASTE already uses for the same
MSVC quirk.
Re-verified against real GCC 16 and Clang at -std=c++11/14/17/20 with
-pedantic -Werror -Wvariadic-macros -Wnoexcept, including the exact
files that failed in CI (unit-udt_macro.cpp, unit-regression2.cpp),
against both the modular headers and the re-amalgamated single header.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix clang-tidy misc-const-correctness in unit-udt_macro.cpp
The four zero-member ONLY_SERIALIZE test objects are only ever read
(via to_json), never mutated, so mark them const per clang-tidy.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix derived-type macro dispatch capping members at 62 instead of 63
NLOHMANN_JSON_GET_MACRO resolves 64 positional arguments, with NAME at
position 65. NLOHMANN_JSON_TYPE_TAG dispatches on Type plus the member
list, so it resolves correctly up to the 63 members NLOHMANN_JSON_PASTE
supports. NLOHMANN_JSON_DERIVED_TYPE_TAG dispatched on the two-token
Type,BaseType prefix plus the member list, running out one slot early:
at 63 members, position 65 landed on the last member name instead of a
sentinel and NLOHMANN_JSON_CAT built an undefined identifier such as
NLOHMANN_JSON_DEFINE_DERIVED_TYPE_INTRUSIVE_m63, with the compiler
reporting "unknown type name 'm1'" once per member and nothing pointing
at an argument-count limit.
That silently reduced all six NLOHMANN_DEFINE_DERIVED_TYPE_* macros from
63 members to 62, contradicting the "up to 63 members" contract in
docs/mkdocs/docs/api/macros/nlohmann_define_derived_type.md.
Drop the leading Type and defer to NLOHMANN_JSON_TYPE_TAG so the tag is
computed from BaseType plus the member list, which fits the available
slots. The zero-own-member derived bodies are therefore selected by tag
1 rather than 2, and the sentinel table for the derived tag is no longer
needed.
Add a regression test at the documented maximum for both the plain and
the derived macros; it fails to compile against the previous dispatch.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Name the zero-member macro bodies by intent, not argument count
The dispatch tag was the literal token 1 or N, pasted onto a macro prefix
to select the zero-member or member-carrying body. For the derived-type
macros that reads wrong: their tag is computed after dropping the leading
Type, so the zero-member body was named _1 while taking two parameters
(Type, BaseType).
Emit EMPTY and MEMBERS instead. The mechanism is unchanged -- the tag is
still a token pasted onto the prefix by NLOHMANN_JSON_CAT -- but the body
names now say what they are rather than encoding an argument count that
only lines up for half of the macros.
Collapse the four duplicated zero-member bodies while here: with no
members there is nothing to default, so each _WITH_DEFAULT_EMPTY body was
a byte-for-byte copy of its plain counterpart. They are now one-line
aliases, leaving a single definition of what an empty object serializes
to per intrusive/non-intrusive and base/derived combination.
No functional change: for both zero-member and member-carrying types the
preprocessed to_json/from_json output is token-for-token identical, and
the arity limits are unchanged (63 members, base and derived).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Document zero-member support in the macro API reference
docs/mkdocs/docs/features/arbitrary_types.md already gained a note, but
the three api/macros pages are where the parameter contract is actually
specified and they still described member as a non-empty list.
State that the list may be empty on each page, and add a note showing
what the zero-member case generates: an empty JSON object for the plain
macros, and base-type-only serialization for the derived ones. Both notes
record that the WITH_NAMES variants do not support this.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Keep user macros named EMPTY or MEMBERS out of the member-count dispatch
The dispatch produced the bare token EMPTY or MEMBERS and pasted it onto
the macro prefix afterwards. In between, the token was rescanned, so a
user macro with either name replaced it: with `#define MEMBERS x` in
scope, even NLOHMANN_DEFINE_TYPE_INTRUSIVE(A, member) -- which compiled
before -- expanded to garbage, and `#define EMPTY` broke the zero-member
form.
Paste the suffix onto the prefix directly in the GET_MACRO slot table
instead. Operands of ## are not macro-expanded, so the selected body name
is formed before any user macro can interfere. NLOHMANN_JSON_TYPE_TAG and
NLOHMANN_JSON_DERIVED_TYPE_TAG become NLOHMANN_JSON_TYPE_BODY and
NLOHMANN_JSON_DERIVED_TYPE_BODY, taking the prefix as their first
argument; NLOHMANN_JSON_CAT is no longer needed. The body macro names are
unchanged, and so is the generated code.
Add a regression test that defines EMPTY and MEMBERS around plain and
derived types, with and without members.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Test for EMPTY and MEMBERS so -Wunused-macros accepts them
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Add new macros for named conversions
* Unit tests for the named conversion macros
* Update the docs to include the new macros
* Fix the documentation for the macros
the correct maximum number of member variables is 63
* Fix CI tests
* update the named macros
* move the example files
* update the explicit macros expansion
* update documentation
* fix documentation hiccups
* astyle changes
* add static analysis exceptions
* change md header to explicit html to fit the length
* Small corrections to docs
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
Signed-off-by: George Sedov <radist.morse@gmail.com>
---------
Signed-off-by: George Sedov <radist.morse@gmail.com>
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
* Support any basic_json type in NLOHMANN_DEFINE_TYPE_* macros
Signed-off-by: kimci86 <kimci86@hotmail.fr>
* Test NLOHMANN_DEFINE_TYPE_* macros also support unordered_json
Signed-off-by: kimci86 <kimci86@hotmail.fr>
* Simplify test about NLOHMANN_DEFINE_TYPE_ with many arguments
Signed-off-by: kimci86 <kimci86@hotmail.fr>
* Remove extra scope in macros tests
Signed-off-by: kimci86 <kimci86@hotmail.fr>
* Remove unused test class in macros tests
Signed-off-by: kimci86 <kimci86@hotmail.fr>
* Update documentation about NLOHMANN_DEFINE_TYPE_* macros
Signed-off-by: kimci86 <kimci86@hotmail.fr>
* Fix NLOHMANN_JSON_SERIALIZE_ENUM documentation
Signed-off-by: kimci86 <kimci86@hotmail.fr>
* Mark some variables const in macros tests, fixes clang-tidy
Signed-off-by: kimci86 <kimci86@hotmail.fr>
* Workaround clang 3.5 issue with const object initialization
Signed-off-by: kimci86 <kimci86@hotmail.fr>
* Update highlighted lines in NLOHMANN_DEFINE_TYPE_* macros examples
Signed-off-by: kimci86 <kimci86@hotmail.fr>
* Fix swapped macros in documentation
Signed-off-by: kimci86 <kimci86@hotmail.fr>
* Remove extra backslashes at the end of macros
Signed-off-by: kimci86 <kimci86@hotmail.fr>
* Require basic_json type in NLOHMANN_DEFINE_TYPE_* generated functions
Signed-off-by: kimci86 <kimci86@hotmail.fr>
* Fix typos in macros documentation
Signed-off-by: kimci86 <kimci86@hotmail.fr>
---------
Signed-off-by: kimci86 <kimci86@hotmail.fr>
* change NLOHMANN_JSON_FROM_WITH_DEFAULT to let NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT work with an empty JSON instance
* fix ci_static_analysis_clang (ci_clang_tidy)
* change NLOHMANN_JSON_FROM_WITH_DEFAULT to let NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT work with an empty JSON instance
Niels Lohmann
George SedovandNiels Lohmann
kimci86
Nissim Armand Ben Danan
Einars Netlis-Galejs
Niccolò IardellaandNiccolò Iardella
Vyacheslav Zhdanovskiy
