* Reserve capacity in from_json() object conversion when supported
The object-to-container from_json() overload filled the target
container one element at a time without reserving capacity, even
when the target type supports reserve() (e.g. std::unordered_map)
and the number of elements is already known. This caused unnecessary
rehashing while parsing large objects into such containers.
Add a reserve-detecting overload (from_json_object_impl), mirroring
the priority_tag-based SFINAE technique already used by the array
conversion path (from_json_array_impl), so that reserve(size()) is
called up front when available and the loop falls back unchanged
otherwise (e.g. for std::map).
Fixes#5406
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Update doc example outputs for new object-conversion iteration order
Reserving capacity in from_json()'s object-conversion path before
inserting elements changes libstdc++'s std::unordered_map bucket
layout, which changes the iteration order used by
get__ValueType_const.cpp, get_to.cpp and operator__ValueType.cpp to
print the elements of a converted std::unordered_map<std::string,
json>. Verified against a clean develop checkout (built with the
same GCC/libstdc++ used in CI) that the old order was produced
without this PR's change and the new order is produced with it, and
that the three affected examples now match their updated expected
output byte-for-byte.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Factor out a reserve-dispatch helper instead of duplicating the object from_json loop
Addresses review feedback from @gregmarr on PR #5472: the emplace loop no
longer needs to exist twice for the reserve/no-reserve cases. A small
from_json_object_reserve() overload pair (SFINAE-dispatched on whether
reserve() exists, mirroring the priority_tag technique used elsewhere)
either calls reserve() or is a no-op; from_json_object_impl() calls it once.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Inline from_json_object_impl into from_json now that it is called only once
Addresses review feedback from @gregmarr on PR #5472: with the reserve
loop de-duplicated, from_json_object_impl no longer needs to be a
separate function that from_json immediately delegates to.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Document std::optional<T> direct-init/copy-init limitation with null
Add regression test pinning current behavior (CHECK_THROWS_AS) in the null
section of unit-conversions.cpp with detailed comment explaining the C++
language-level cause (std::optional's own converting constructor wins
overload resolution over basic_json::operator T()).
Add a warning callout in conversions.md documenting that direct construction/
assignment of std::optional<T> from JSON null throws type_error 302, with a
clear workaround (use get<std::optional<T>>() or get_to() instead, which
correctly produce std::nullopt).
This is a limitation at the language level: there is no SFINAE path to
distinguish "called from inside std::optional's own constructor" from "direct
call", so fixing it would require breaking changes to operator ValueType().
A permanent fix belongs in the 4.0 type-strictness redesign (#3453).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-Authored-By: Claude Code <noreply@anthropic.com>
* Fix issue reference in std::optional test comment
Update the comment in the null section test to reference #5246 instead of
placeholder #XXXX, clarifying where the direct-init/copy-init limitation is tracked.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Use CHECK_THROWS_AS_WITH for std::optional test assertions
Update the regression tests to use CHECK_THROWS_AS_WITH instead of
CHECK_THROWS_AS to verify both the exception type and the error message.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix CI: use CHECK_THROWS_WITH_AS, the macro that actually exists
CHECK_THROWS_AS_WITH is not a doctest macro; the correct one used throughout
this test suite is CHECK_THROWS_WITH_AS(expr, message, exception_type&), with
the message before the type and the type as a reference. The previous commit
didn't catch this because it only compiled the file standalone with default
settings; this TEST_CASE only compiles under
`#if !JSON_USE_IMPLICIT_CONVERSIONS`, which is why ci_test_noimplicitconversions
was the job that failed. Verified by building and running the test in that
exact configuration (JSON_USE_IMPLICIT_CONVERSIONS=0): 14/14 assertions pass.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Run std::optional test under default implicit-conversions build too
TEST_CASE("std::optional") was guarded by #if !JSON_USE_IMPLICIT_CONVERSIONS,
so it only ever compiled in the non-default build with implicit conversions
disabled. This traces back to commit 1d7688aef (fixes#3859), which changed a
previously dead #ifndef JSON_USE_IMPLICIT_CONVERSIONS guard (the macro is
always defined by that point, so it never held) to #if !JSON_USE_IMPLICIT_CONVERSIONS
-- making the test compile for the first time, but only in the disabled-conversions
build. As a result, std::optional support had zero test coverage in the default
configuration almost every user builds with.
Verified the entire test case (all sections: null, string, bool, number, array,
object) compiles and passes identically with JSON_USE_IMPLICIT_CONVERSIONS both
on (default) and off -- nothing in it actually depends on the setting. Removing
the guard closes the coverage gap with no behavior change: 285 assertions pass
with implicit conversions on, 232 with them off (the difference comes from
other, unrelated conditionally-compiled tests in this file).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* 🚨 fix warning
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Code <noreply@anthropic.com>
* Added NLOHNMANN_JSON_SERIALIZE_ENUM_STRICT
- duplicate of NLOHMANN_JSON_SERIALIZE_ENUM
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* Added failing tests for NLOHMANN_JSON_SERIALIZE_ENUM_STRICT
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* modified NLOHMANN_JSON_SERIALIZE_STRICT to throw
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* added documentation and changed readme to include NLOHMANN_JSON_SERIALIZE_ENUM_STRICT
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* ran amalgamate
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* docs(macros): add page for JSON_SERIALIZE_ENUM_STRICT
- added page to nav
- added links to new page where appropriate
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* refactor(macros): make JSON_SERIALIZE_ENUM_STRICT use JSON_THROW
- added templated wrapper function to fix scope error in calling JSON_THROW
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* refactor(macros): make NLOHMANN_SERIALIZE_ENUM_STRICT use error code 410
- added error code 410 to docs
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* tests(macros): add test for to_json with enum value not mentioned
in mapping for NLOHMANN_JSON_SERIALIZE_ENUM_STRICT
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* Apply suggestions from code review
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
Signed-off-by: Caillin Nugent <nugentcaillin@gmail.com>
* fix(macro): prevent compilation error with -Werror and -Wunused-parameter
with NLOHMANN_JSON_SERIALIZE_ENUM_STRICT
- casted exception to void to avoid warning
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* fix(docs): add link to NLOHMANN_SERIALIZE_ENUM_STRICT docs to exception page
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* docs(macros): add example of exception throwing for NLOHMANN_JSON_SERIALIZE_ENUM_STRICT
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
* refactor(macros): add more in-depth error message to NLOHMANN_JSON_SERIALIZE_ENUM_STRICT
- changed error message to follow style of nlohmann/json#4989
- made description of throw wrapper more general
- updated tests and example of exceptions
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
---------
Signed-off-by: Caillin Nugent <caillinn@student.unimelb.edu.au>
Signed-off-by: Caillin Nugent <nugentcaillin@gmail.com>
Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>
* Make std::filesystem::path conversion to/from UTF-8 encoded JSON string explicit.
Signed-off-by: Richard Musil <risa2000x@gmail.com>
* Experimental: Changing C++ standard detection logic to accommodate potential corner cases.
Signed-off-by: Richard Musil <risa2000x@gmail.com>
* Drop C++ standard tests for compilers which do not implement required features.
Signed-off-by: Richard Musil <risa2000x@gmail.com>
* Drop C++ standard tests for MSVC versions which do not implement required features.
Signed-off-by: Richard Musil <risa2000x@gmail.com>
---------
Signed-off-by: Richard Musil <risa2000x@gmail.com>
Co-authored-by: Richard Musil <risa2000x@gmail.com>
* 🚧 conversions for std::optional
* 🏁 fix <optional> inclusion
* 💚 overwork tests
* Use JSON_HAS_CPP_17 only after it has been defined
* ✅ update tests
* 🏁 include right <optional> header
* ♻️ do not include experimental headers
* Add missing #endif after rebase
* Fix failing test
* Only define conversion to std::optional when JSON_USE_IMPLICIT_CONVERSION is disabled.
* missing endif
* Remove Wfloat-equal suppress
* amalgamate
* Move include of optional out of macro_scope; probably does not make sense to be there
* Make clang-tidy happy
* Suppress lint instead of changing to 'contains'
---------
Co-authored-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Markus Palonen <markus.palonen@gmail.com>
* Add C++20 3-way comparison operator and fix broken comparisons
Fixes#3207.
Fixes#3409.
* Fix iterators to meet (more) std::ranges requirements
Fixes#3130.
Related discussion: #3408
* Add note about CMake standard version selection to unit tests
Document how CMake chooses which C++ standard version to use when
building tests.
* Update documentation
* CI: add legacy discarded value comparison
* Fix internal linkage errors when building a module
Niels Lohmann
Caillin NugentandNiels Lohmann
risa2000andRichard Musil
peng-wang-cn
Raphael Grimmandbarcode
