Merge remote-tracking branch 'origin/develop' into custom-number-type-fixes

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

# Conflicts:
#	include/nlohmann/detail/output/binary_writer.hpp
#	single_include/nlohmann/json.hpp
This commit is contained in:
Niels Lohmann committed 2026-10-11 11:10:34 +02:00
commit 969f17fae1
110 files changed
+3572 -2047

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+3 -1
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@@ -241,4 +241,6 @@ Strong exception safety: if an exception occurs, the original value stays intact
3. Added in version 3.11.0. Fixed in version 3.13.0 to consistently accept `std::string_view`-convertible keys, as
already supported by [`operator[]`](operator[].md), [`value`](value.md), [`find`](find.md), and other lookup
functions.
4. Added in version 2.0.0.
4. Added in version 2.0.0. Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109) instead of
[`out_of_range.404`](../../home/exceptions.md#jsonexceptionout_of_range404) for a one-character array index that is not
a digit (e.g., `/x`) in version 3.13.0, as it already did for longer ones.
@@ -10,6 +10,10 @@ bool contains(KeyType&& key) const;
// (3)
bool contains(const json_pointer& ptr) const;
// (4)
template<typename T>
bool contains(T) const = delete;
```
1. Check whether an element exists in a JSON object with a key equivalent to `key`. If the element is not found or the
@@ -17,6 +21,9 @@ bool contains(const json_pointer& ptr) const;
2. See 1. This overload is only available if `KeyType` is comparable with `#!cpp typename object_t::key_type` and
`#!cpp typename object_comparator_t::is_transparent` denotes a type.
3. Check whether the given JSON pointer `ptr` can be resolved in the current JSON value.
4. Deleted: this overload is only available if `T` is an integral type and is declared as deleted, so that a call with
an integer `key` (for example, `#!cpp j.contains(0)`) fails to compile. Otherwise, the integer literal `0` would convert to
a null `#!cpp const char*` and, from there, to the key type, causing undefined behavior at runtime.
## Template parameters
@@ -39,6 +46,7 @@ bool contains(const json_pointer& ptr) const;
is not an object, `#!cpp false` is returned.
2. See 1.
3. `#!cpp true` if the JSON pointer can be resolved to a stored value, `#!cpp false` otherwise.
4. Deleted; a call with an integral argument does not compile.
## Exception safety
@@ -49,6 +57,7 @@ Strong exception safety: if an exception occurs, the original value stays intact
1. The function does not throw exceptions.
2. The function does not throw exceptions.
3. The function does not throw exceptions.
4. Deleted; a call with an integral argument does not compile.
## Complexity
+7
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@@ -7,12 +7,19 @@ size_type count(const typename object_t::key_type& key) const;
// (2)
template<typename KeyType>
size_type count(KeyType&& key) const;
// (3)
template<typename T>
size_type count(T) const = delete;
```
1. Returns the number of elements with key `key`. If `ObjectType` is the default `std::map` type, the return value will
always be `0` (`key` was not found) or `1` (`key` was found).
2. See 1. This overload is only available if `KeyType` is comparable with `#!cpp typename object_t::key_type` and
`#!cpp typename object_comparator_t::is_transparent` denotes a type.
3. Deleted: this overload is only available if `T` is an integral type and is declared as deleted, so that a call with
an integer `key` (for example, `#!cpp j.count(0)`) fails to compile. Otherwise, the integer literal `0` would convert to
a null `#!cpp const char*` and, from there, to the key type, causing undefined behavior at runtime.
## Template parameters
@@ -37,8 +37,8 @@ ignore
: ignore invalid UTF-8 sequences; all valid bytes are copied to the output unchanged, and invalid bytes are dropped
keep
: keep invalid UTF-8 sequences unchanged; only meaningful for the binary formats mentioned above, since [`dump`]
(dump.md) itself must produce text, and `keep` there writes the ill-formed bytes to the output as is, so the
: keep invalid UTF-8 sequences unchanged; only meaningful for the binary formats mentioned above, since
[`dump`](dump.md) itself must produce text, and `keep` there writes the ill-formed bytes to the output as is, so the
result is then not valid UTF-8 (but still equals the input bytes exactly, including around any well-formed
characters, which are still escaped as usual)
+9
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@@ -10,12 +10,21 @@ template<typename KeyType>
iterator find(KeyType&& key);
template<typename KeyType>
const_iterator find(KeyType&& key) const;
// (3)
template<typename T>
iterator find(T) = delete;
template<typename T>
const_iterator find(T) const = delete;
```
1. Finds an element in a JSON object with a key equivalent to `key`. If the element is not found or the
JSON value is not an object, `end()` is returned.
2. See 1. This overload is only available if `KeyType` is comparable with `#!cpp typename object_t::key_type` and
`#!cpp typename object_comparator_t::is_transparent` denotes a type.
3. Deleted: this overload is only available if `T` is an integral type and is declared as deleted, so that a call with
an integer `key` (for example, `#!cpp j.find(0)`) fails to compile. Otherwise, the integer literal `0` would convert to
a null `#!cpp const char*` and, from there, to the key type, causing undefined behavior at runtime.
## Template parameters
@@ -124,7 +124,8 @@ Linear in the size of the input.
!!! warning "Deprecation"
- Overload (2) replaces calls to `from_bjdata` with a pointer and a length as first two parameters, which has been
deprecated in version 3.13.0. This overload will be removed in version 4.0.0. Please replace all calls like
deprecated in version 3.13.0. In version 4.0.0, this overload
will be deleted (`= delete`) rather than removed. Please replace all calls like
`#!cpp from_bjdata(ptr, len, ...);` with `#!cpp from_bjdata(ptr, ptr+len, ...);`.
You should be warned by your compiler with a `-Wdeprecated-declarations` warning if you are using a deprecated
+2 -1
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@@ -110,7 +110,8 @@ Linear in the size of the input.
!!! warning "Deprecation"
- Overload (2) replaces calls to `from_bon8` with a pointer and a length as first two parameters, which has been
deprecated in version 3.13.0. This overload will be removed in version 4.0.0. Please replace all calls like
deprecated in version 3.13.0. In version 4.0.0, this overload
will be deleted (`= delete`) rather than removed. Please replace all calls like
`#!cpp from_bon8(ptr, len, ...);` with `#!cpp from_bon8(ptr, ptr+len, ...);`.
You should be warned by your compiler with a `-Wdeprecated-declarations` warning if you are using a deprecated
+2 -1
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@@ -126,7 +126,8 @@ Linear in the size of the input.
!!! warning "Deprecation"
- Overload (2) replaces calls to `from_bson` with a pointer and a length as first two parameters, which has been
deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
deprecated in version 3.8.0. In version 4.0.0, this overload
will be deleted (`= delete`) rather than removed. Please replace all calls like
`#!cpp from_bson(ptr, len, ...);` with `#!cpp from_bson(ptr, ptr+len, ...);`.
- Overload (2) replaces calls to `from_bson` with a pair of iterators as their first parameter, which has been
deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
+2 -1
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@@ -135,7 +135,8 @@ Linear in the size of the input.
!!! warning "Deprecation"
- Overload (2) replaces calls to `from_cbor` with a pointer and a length as first two parameters, which has been
deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
deprecated in version 3.8.0. In version 4.0.0, this overload
will be deleted (`= delete`) rather than removed. Please replace all calls like
`#!cpp from_cbor(ptr, len, ...);` with `#!cpp from_cbor(ptr, ptr+len, ...);`.
- Overload (2) replaces calls to `from_cbor` with a pair of iterators as their first parameter, which has been
deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
@@ -127,7 +127,8 @@ Linear in the size of the input.
!!! warning "Deprecation"
- Overload (2) replaces calls to `from_msgpack` with a pointer and a length as first two parameters, which has been
deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
deprecated in version 3.8.0. In version 4.0.0, this overload
will be deleted (`= delete`) rather than removed. Please replace all calls like
`#!cpp from_msgpack(ptr, len, ...);` with `#!cpp from_msgpack(ptr, ptr+len, ...);`.
- Overload (2) replaces calls to `from_msgpack` with a pair of iterators as their first parameter, which has been
deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
@@ -125,7 +125,8 @@ Linear in the size of the input.
!!! warning "Deprecation"
- Overload (2) replaces calls to `from_ubjson` with a pointer and a length as first two parameters, which has been
deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
deprecated in version 3.8.0. In version 4.0.0, this overload
will be deleted (`= delete`) rather than removed. Please replace all calls like
`#!cpp from_ubjson(ptr, len, ...);` with `#!cpp from_ubjson(ptr, ptr+len, ...);`.
- Overload (2) replaces calls to `from_ubjson` with a pair of iterators as their first parameter, which has been
deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
@@ -62,5 +62,5 @@ same name. Hidden members remain accessible via [`as_base_class`](as_base_class.
## Version history
- Added in version 3.12.0.
- Added in version 3.11.3.
- Made a public member type in version 3.13.0; it was private before, so it could not be named outside the class.
+1 -2
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@@ -26,8 +26,7 @@ To store objects in C++, a type is defined by the template parameters described
`StringType`
: the type of the keys or names (e.g., `std::string`). The comparison function `std::less<StringType>` is used to
order elements inside the container. `object_t::key_type` must be implicitly convertible to `string_t` (required by the
binary formats).
order elements inside the container.
`AllocatorType`
: the allocator to use for objects (e.g., `std::allocator`)
@@ -286,4 +286,6 @@ Strong exception safety: if an exception occurs, the original value stays intact
3. Added in version 3.11.0. Fixed in version 3.13.0 to consistently accept `std::string_view`-convertible keys, as
already supported by [`at`](at.md), [`value`](value.md), [`find`](find.md), and other lookup functions.
4. Added in version 2.0.0. A missing array index in the const version is guarded by a runtime assertion since
version 3.13.0.
version 3.13.0. Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109) instead of
[`out_of_range.404`](../../home/exceptions.md#jsonexceptionout_of_range404) for a one-character array index that is not
a digit (e.g., `/x`) in version 3.13.0, as it already did for longer ones.
+3
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@@ -112,3 +112,6 @@ is thrown. In any case, the original value is not changed: the patch is applied
location has a non-object/non-array parent in version 3.13.0.
- Added [`out_of_range.414`](../../home/exceptions.md#jsonexceptionout_of_range414) and rejected a "move" operation whose "from" location is a proper
prefix of its "path" location instead of silently producing a corrupted result in version 3.13.0.
- Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109) instead of
[`out_of_range.404`](../../home/exceptions.md#jsonexceptionout_of_range404) for a one-character array index that is
not a digit (e.g., `/x`) in version 3.13.0, as it already did for longer ones.
@@ -110,3 +110,6 @@ function throws an exception.
location has a non-object/non-array parent in version 3.13.0.
- Added [`out_of_range.414`](../../home/exceptions.md#jsonexceptionout_of_range414) and rejected a "move" operation whose "from" location is a proper
prefix of its "path" location instead of silently producing a corrupted result in version 3.13.0.
- Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109) instead of
[`out_of_range.404`](../../home/exceptions.md#jsonexceptionout_of_range404) for a one-character array index that is
not a digit (e.g., `/x`) in version 3.13.0, as it already did for longer ones.
@@ -42,6 +42,8 @@ With (2), the bytes written before the exception remain in the output adapter.
integer beyond int64), which BON8 cannot represent
- Throws [type_error.316](../../home/exceptions.md#jsonexceptiontype_error316) if `j` contains a string that is not
valid UTF-8
- Throws [type_error.321](../../home/exceptions.md#jsonexceptiontype_error321) if `j` or a value nested in it is
discarded; example: `"cannot serialize discarded value to BON8"`
## Complexity
+6 -2
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@@ -36,8 +36,9 @@ The function can throw the following exceptions:
- Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109) if an array index in a key is not a
number; example: `"array index 'one' is not a number"`
- Throws [`out_of_range.404`](../../home/exceptions.md#jsonexceptionout_of_range404) if a level becomes an array
(because one of its keys is `0`) and another key at that level cannot be an array index; example:
`"unresolved reference token 'x'"`
(because one of its keys is `0`) and another key at that level begins with a digit but is not a valid array index
(such as `1a`), or is `-`; example:
`"unresolved reference token '-'"`
## Complexity
@@ -80,3 +81,6 @@ Apart from these two cases, for a JSON value `j`, the following is always true:
- Added in version 2.0.0.
- Made the array/object decision independent of the object's iteration order in version 3.13.0.
- Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109) instead of
[`out_of_range.404`](../../home/exceptions.md#jsonexceptionout_of_range404) for a one-character array index that is
not a digit (e.g., `/x`) in version 3.13.0, as it already did for longer ones.
+11 -1
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@@ -119,6 +119,14 @@ changes to any JSON value.
## Notes
!!! warning "`null` members are not missing"
The default value is used only if the key (or JSON Pointer) does not exist. A member that exists but is
`#!json null` is converted like any other value, so `#!cpp j.value("k", 0)` throws a
[`type_error.302`](../../home/exceptions.md#jsonexceptiontype_error302) if `"k"` is `#!json null`. See
[Access with default value](../../features/element_access/default_value.md)
for alternatives.
!!! warning "Return type"
The value function is a template, and the return type of the function is determined by the type of the provided
@@ -227,4 +235,6 @@ changes to any JSON value.
[`operator[]`](operator[].md), [`at`](at.md), [`find`](find.md), and other lookup functions.
3. Added in version 2.0.2. Extended to work with arrays in version 3.13.0, including fixing an issue where resolving
`ptr` through an array unexpectedly threw `out_of_range` instead of returning the resolved element (or
`default_value`, as documented).
`default_value`, as documented). Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109)
instead of returning `default_value` for a one-character array index that is not a digit (e.g., `/x`) in version
3.13.0, as it already did for longer ones.
+1
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@@ -27,6 +27,7 @@ header. See also the [macro overview page](../../features/macros.md).
- [**JSON_HAS_CPP_11**<br>**JSON_HAS_CPP_14**<br>**JSON_HAS_CPP_17**<br>**JSON_HAS_CPP_20**](json_has_cpp_11.md) - set supported C++ standard
- [**JSON_HAS_FILESYSTEM**<br>**JSON_HAS_EXPERIMENTAL_FILESYSTEM**](json_has_filesystem.md) - control `std::filesystem` support
- [**JSON_HAS_RANGE_VIEW_CONVERSION**](json_has_range_view_conversion.md) - control construction from `std::ranges` views
- [**JSON_HAS_RANGES**](json_has_ranges.md) - control `std::ranges` support
- [**JSON_HAS_STATIC_RTTI**](json_has_static_rtti.md) - control RTTI (run time type information) support
- [**JSON_HAS_STD_FORMAT**](json_has_std_format.md) - control `std::format`/`std::formatter` support
@@ -49,6 +49,6 @@ The default value is detected based on preprocessor macros such as `#!cpp __cplu
## Version history
- Added in version 3.10.5.
- Added in version 3.10.0.
- Added `JSON_HAS_CPP_23` in version 3.12.0.
- Added `JSON_HAS_CPP_26` in version 3.13.0.
@@ -0,0 +1,43 @@
# JSON_HAS_RANGE_VIEW_CONVERSION
```cpp
#define JSON_HAS_RANGE_VIEW_CONVERSION /* value */
```
This macro indicates whether a JSON array can be constructed directly from a C++20 range view (`std::ranges::view`),
such as the result of `std::views::filter` or `std::views::transform`. Possible values are `1` when supported or `0`
when unsupported.
## Default definition
The default value is `1` if [`JSON_HAS_RANGES`](json_has_ranges.md) is `1` and the compiler is not MinGW (that is,
`#!cpp __MINGW32__` is not defined), and `0` otherwise.
When the macro is not defined, the library will define it to its default value.
!!! info "Known compiler/stdlib exclusions"
- **MinGW** -- disabled, because its `std::ranges` support is incomplete ([issue #4916](https://github.com/nlohmann/json/issues/4916)).
- All toolchains for which [`JSON_HAS_RANGES`](json_has_ranges.md#default-definition) is disabled.
## Examples
??? example
The code below forces the library to disable the conversion from range views:
```cpp
#define JSON_HAS_RANGE_VIEW_CONVERSION 0
#include <nlohmann/json.hpp>
...
```
## See also
- [JSON_HAS_RANGES](json_has_ranges.md) - control `std::ranges` support
- [Constructing from a C++20 range view](../../features/conversions.md#putting-values-in) - usage of the feature
## Version history
- Added in version 3.13.0.
@@ -20,7 +20,7 @@ When the macro is not defined, the library will define it to its default value.
- **GCC 11.1.0** — disabled (the shipped `<ranges>` header has a syntax error; [issue #4440](https://github.com/nlohmann/json/issues/4440))
- **libstdc++ < 11** — disabled (incomplete C++20 ranges support; [issue #4440](https://github.com/nlohmann/json/issues/4440))
- **Clang < 16 with libstdc++** — disabled (incomplete ranges support; [issue #4440](https://github.com/nlohmann/json/issues/4440))
- **Clang < 16 with libstdc++** — disabled (incomplete ranges support; [issue #5161](https://github.com/nlohmann/json/issues/5161))
- **libc++ < 160000** — disabled (incomplete C++20 ranges support; [issue #4440](https://github.com/nlohmann/json/issues/4440))
- **nvcc (CUDA) 12.0.x and 12.1.x** — disabled (the `enable_borrowed_range` variable-template syntax triggers a parse error
under these two toolkit versions; fixed in CUDA 12.2; [issue #3907](https://github.com/nlohmann/json/issues/3907))
@@ -44,9 +44,12 @@ When the macro is not defined, the library will define it to its default value.
- [JSON_HAS_CPP_11 / JSON_HAS_CPP_14 / JSON_HAS_CPP_17 / JSON_HAS_CPP_20 / JSON_HAS_CPP_23 /
JSON_HAS_CPP_26](json_has_cpp_11.md) - set supported C++ standard
- [JSON_HAS_RANGE_VIEW_CONVERSION](json_has_range_view_conversion.md) - control construction from `std::ranges` views
- [JSON_HAS_STD_FORMAT](json_has_std_format.md) - a similar feature-detection macro, for `std::format`/`std::formatter`
support
## Version history
- Added in version 3.11.0.
- Added the exclusions for libstdc++ < 11, Clang < 16 with libstdc++, libc++ < 16, and nvcc (CUDA) 12.0.x and 12.1.x in
version 3.13.0. Before, only GCC 11.1.0 was excluded.
@@ -20,7 +20,10 @@ The macro does not affect:
- The binary readers ([`from_cbor`](../basic_json/from_cbor.md), [`from_msgpack`](../basic_json/from_msgpack.md),
[`from_ubjson`](../basic_json/from_ubjson.md), [`from_bjdata`](../basic_json/from_bjdata.md),
[`from_bson`](../basic_json/from_bson.md)): none of these formats requires a decoder to reject ill-formed UTF-8, so
they always return the bytes unchanged.
by default they return the bytes unchanged (`error_handler_t::keep`), independent of this macro. Pass an
`error_handler` argument explicitly to validate or sanitize the strings they read.
- [`from_bon8`](../basic_json/from_bon8.md): BON8 always validates, because the UTF-8 lead bytes mark where a string
ends.
## Default definition
@@ -190,3 +190,5 @@ void to_json(BasicJsonType& j, const B& b) {
4. Added in version 3.12.0.
5. Added in version 3.12.0.
6. Added in version 3.12.0.
All six macros were changed to allow an empty member list in version 3.13.0.
@@ -186,3 +186,6 @@ See the examples below for the concrete generated code.
1. Added in version 3.9.0.
2. Added in version 3.11.0.
3. Added in version 3.11.3.
All three macros were changed to work with any `basic_json` specialization (not only `nlohmann::json`) in version 3.12.0,
and to allow an empty member list in version 3.13.0.
@@ -185,3 +185,6 @@ See the examples below for the concrete generated code.
1. Added in version 3.9.0.
2. Added in version 3.11.0.
3. Added in version 3.11.3.
All three macros were changed to work with any `basic_json` specialization (not only `nlohmann::json`) in version 3.12.0,
and to allow an empty member list in version 3.13.0.
@@ -38,4 +38,6 @@ the library.
## Version history
- Added in version 3.11.0. Changed inline namespace name in version 3.11.2.
- Added in version 3.11.0. Changed inline namespace name in version 3.11.2. Added the ABI tag `_dp` in
version 3.12.0, and the ABI tags `_bics`, `_psp`, `_snul`, `_sbu8`, and `_ekmo` in version 3.13.0; see
[`nlohmann` Namespace](../../features/namespace.md#structure).
@@ -14,7 +14,7 @@ These macros can be used to open and close the `nlohmann` namespace. See
## Default definition
The default definitions open and close the `nlohmann` namespace. The precise definition of
[`NLOHMANN_JSON_NAMESPACE_BEGIN`] varies as described [here](../../features/namespace.md#structure).
`NLOHMANN_JSON_NAMESPACE_BEGIN` varies as described [here](../../features/namespace.md#structure).
1. Default definition of `NLOHMANN_JSON_NAMESPACE_BEGIN`:
+1 -1
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@@ -10,7 +10,7 @@ The library parses, stores, and serializes JSON values in memory. It does not op
files (it only reads from streams or `std::FILE*` handles that the caller has already opened), does not read environment
variables, and does not implement cryptography or handle credentials.
The primary threat is therefore **untrusted input**: JSON text or binary data (BJData, BSON, CBOR, MessagePack, UBJSON)
The primary threat is therefore **untrusted input**: JSON text or binary data (BJData, BON8, BSON, CBOR, MessagePack, UBJSON)
that an attacker controls, passed to [`parse`](../api/basic_json/parse.md), [`accept`](../api/basic_json/accept.md),
[`sax_parse`](../api/basic_json/sax_parse.md), or one of the `from_*` functions such as
[`from_cbor`](../api/basic_json/from_cbor.md). Such input may try to
@@ -12,7 +12,7 @@ violations will result in a failed build.
Note: C++20 modules support may hit compiler-specific issues not covered by the general compiler matrix below. See [Modules](../features/modules.md#known-issues) for known issues and workarounds.
Note: Some modern features (like C++20 ranges or filesystem support) may be disabled on specific broken or incomplete toolchains even when standard feature-test macros indicate support. See [`JSON_HAS_RANGES`](../api/macros/json_has_ranges.md) and [`JSON_HAS_FILESYSTEM`](../api/macros/json_has_filesystem.md) for details on known exclusions.
Note: Some modern features (like C++20 ranges or filesystem support) may be disabled on specific broken or incomplete toolchains even when standard feature-test macros indicate support. See [`JSON_HAS_RANGES`](../api/macros/json_has_ranges.md), [`JSON_HAS_RANGE_VIEW_CONVERSION`](../api/macros/json_has_range_view_conversion.md), and [`JSON_HAS_FILESYSTEM`](../api/macros/json_has_filesystem.md) for details on known exclusions.
- [x] The library is compiled with 50+ different C++ compilers with different operating systems and platforms,
including the oldest versions known to compile the library.
@@ -107,7 +107,7 @@ Note: Some modern features (like C++20 ranges or filesystem support) may be disa
- [x] The library is compiled with all C++ language revisions (C++11, C++14, C++17, C++20, C++23, and C++26) to detect
and fix language deprecations early.
- [x] The library is checked for compiler warnings:
- On Clang, `-Weverything` is used with 8 exceptions.
- On Clang, `-Weverything` is used with 7 exceptions.
??? abstract "Clang warnings"
@@ -347,6 +347,13 @@ struct adl_serializer<boost::optional<T>> {
NLOHMANN_JSON_NAMESPACE_END
```
!!! tip "`std::optional` needs no serializer"
Since version 3.12.0, `std::optional<T>` is supported out of the box when compiling with C++17
(`std::nullopt` is converted to and from `null`). Do not write an `adl_serializer` for it; this pattern is only
needed for types such as `boost::optional` or for custom semantics. See [Conversions](conversions.md) and
[Omitting a field when serializing `std::optional`](conversions.md#omitting-a-field-when-serializing-stdoptional).
!!! note "ABI compatibility"
Use [`NLOHMANN_JSON_NAMESPACE_BEGIN`](../api/macros/nlohmann_json_namespace_begin.md) and `NLOHMANN_JSON_NAMESPACE_END`
+2 -1
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@@ -217,7 +217,8 @@ json j = numbers; // [1,2,3]
```
This requires [`JSON_HAS_RANGES`](../api/macros/json_has_ranges.md) to be enabled and is unavailable on MinGW due
to incomplete C++20 ranges support there.
to incomplete C++20 ranges support there; see
[`JSON_HAS_RANGE_VIEW_CONVERSION`](../api/macros/json_has_range_view_conversion.md).
## Your own types
@@ -30,6 +30,47 @@ you want to access and a default value in case there is no value stored with tha
| `#!cpp j.value("append", false)` | `#!json true` |
| `#!cpp j.value("logLevel", "verbose")` | `#!json "verbose"` |
## Nested values
To read a value deep inside a document, pass a [JSON Pointer](../json_pointer.md) instead of a key. The default value is
returned if the value at the pointer does not exist, including the case that an intermediate key is missing. There is
no need to check each level with [`contains`](../../api/basic_json/contains.md) first.
```cpp
json j = {{"server", {{"port", 8080}}}, {"list", {10, 20}}};
int port = j.value("/server/port"_json_pointer, 80); // 8080
int timeout = j.value("/server/limits/timeout"_json_pointer, 30); // 30 (missing intermediate key)
int second = j.value("/list/1"_json_pointer, 0); // 20 (numeric tokens index arrays)
int third = j.value("/list/5"_json_pointer, 0); // 0 (index out of range)
bool has_port = j.contains("/server/port"_json_pointer); // true
bool has_host = j.contains("/server/host/name"_json_pointer); // false
```
If the path is only available as a dotted string such as `#!cpp "server.port"`, do not build the pointer by
concatenating `#!cpp "/"` and the parts: keys containing `/` or `~` would be misinterpreted. Append each part as a
reference token with [`operator/=`](../../api/json_pointer/operator_slasheq.md) instead. It escapes the token for you.
```cpp
json::json_pointer to_pointer(const std::string& dotted)
{
json::json_pointer ptr;
std::istringstream in(dotted);
for (std::string token; std::getline(in, token, '.');)
{
ptr /= token;
}
return ptr;
}
int port = j.value(to_pointer("server.port"), 80); // 8080
int first = j.value(to_pointer("list.0"), 0); // 10
```
The key `#!cpp "a/b"` yields the pointer `#!cpp "/a~1b"`; the dot-splitting itself is up to the caller, so keys
containing `.` need a different separator.
## Notes
!!! failure "Exceptions"
@@ -37,6 +78,31 @@ you want to access and a default value in case there is no value stored with tha
- With string keys, `value` can only be used with objects. For other types, a [`basic_json::type_error`](../../home/exceptions.md#jsonexceptiontype_error306) is thrown.
- With JSON Pointers, `value` can be used with both objects and arrays. For other types (null, boolean, number, string), a [`basic_json::type_error`](../../home/exceptions.md#jsonexceptiontype_error306) is thrown.
!!! warning "`null` and mistyped members are not missing"
`value` returns the default value only if the key is **absent**. If the member exists, it is converted to the type
of the default value, even if it is `#!json null`. For `#!json {"k": null}`, the call `#!cpp j.value("k", 0)` throws
a [`basic_json::type_error`](../../home/exceptions.md#jsonexceptiontype_error302), and so does a member of another
type such as a string where a number is expected. The same holds for JSON Pointers.
To treat `#!json null` like a missing value, check for it explicitly:
```cpp
int n = (j.contains("k") && !j["k"].is_null()) ? j["k"].get<int>() : 0;
```
With C++17, [`get<std::optional<T>>()`](../../api/basic_json/get.md) maps `#!json null` to an empty optional. As
[`at`](../../api/basic_json/at.md) throws [`out_of_range`](../../home/exceptions.md#jsonexceptionout_of_range403)
for an absent key, use [`find`](../../api/basic_json/find.md) to cover both cases:
```cpp
std::optional<int> n; // empty if "k" is absent or null
if (const auto it = j.find("k"); it != j.end())
{
n = it->get<std::optional<int>>(); // still throws for a non-number such as "text"
}
```
!!! warning "Return type"
The value function is a template, and the return type of the function is determined by the type of the provided
@@ -63,3 +129,6 @@ you want to access and a default value in case there is no value stored with tha
- [`value`](../../api/basic_json/value.md) for access with default value
- documentation on [checked access](checked_access.md)
- documentation on [JSON Pointer](../json_pointer.md)
- [`contains`](../../api/basic_json/contains.md) to check whether a key or JSON Pointer exists
- [`json_pointer::operator/=`](../../api/json_pointer/operator_slasheq.md) to build a pointer token by token
@@ -77,6 +77,10 @@ auto val2 = j.at(json::json_pointer("/nested/three/1")); // false
auto val3 = j.value(json::json_pointer("/nested/four"), 0); // 0
```
To read a value with a fallback, use [`value`](../api/basic_json/value.md) with a JSON Pointer; to test for existence,
use [`contains`](../api/basic_json/contains.md). Neither needs intermediate checks, see
[Nested values](element_access/default_value.md#nested-values).
!!! note "Creating intermediate levels that don't exist"
See the [`operator[]` notes](../api/basic_json/operator%5B%5D.md#return-value) for how array vs. object is
@@ -126,6 +130,8 @@ auto j_original = j_flat.unflatten();
## See also
- Class [`json_pointer`](../api/json_pointer/index.md)
- Functions [`value`](../api/basic_json/value.md), [`contains`](../api/basic_json/contains.md), and
[`at`](../api/basic_json/at.md) accept JSON Pointers; see [Nested values](element_access/default_value.md#nested-values)
- Function [`flatten`](../api/basic_json/flatten.md)
- Function [`unflatten`](../api/basic_json/unflatten.md)
- [JSON Patch](json_patch.md) - paths inside a patch are JSON Pointers
+39
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@@ -82,6 +82,45 @@ To override the built-in check, define `JSON_HAS_FILESYSTEM` or `JSON_HAS_EXPERI
See [full documentation of `JSON_HAS_FILESYSTEM` and `JSON_HAS_EXPERIMENTAL_FILESYSTEM`](../api/macros/json_has_filesystem.md).
## `JSON_HAS_RANGES`
The library uses `std::ranges` (and concepts) where available, for example, to parse from C++20 ranges and to
construct JSON arrays from range views. The library detects whether the standard library supports ranges and
disables the support on toolchains with an incomplete implementation. To override the built-in check, define
`JSON_HAS_RANGES` to `1` or `0`.
See [full documentation of `JSON_HAS_RANGES`](../api/macros/json_has_ranges.md).
## `JSON_HAS_RANGE_VIEW_CONVERSION`
When `JSON_HAS_RANGES` is enabled (and the compiler is not MinGW), a JSON array can be constructed directly from a C++20
range view such as `std::views::filter(...)`. To override the built-in check, define `JSON_HAS_RANGE_VIEW_CONVERSION` to
`1` or `0`.
See [full documentation of `JSON_HAS_RANGE_VIEW_CONVERSION`](../api/macros/json_has_range_view_conversion.md).
## `JSON_HAS_STATIC_RTTI`
The library detects whether the compiler supports run time type information (RTTI), which it needs, for instance, to
exclude `std::any` from the candidate types of the implicit conversion on C++17. To override the built-in check, define
`JSON_HAS_STATIC_RTTI` to `1` or `0`.
See [full documentation of `JSON_HAS_STATIC_RTTI`](../api/macros/json_has_static_rtti.md).
## `JSON_HAS_STD_FORMAT`
When compiling with C++20 and a standard library that provides `<format>`, the library provides a `std::formatter`
specialization for JSON values. To override the built-in check, define `JSON_HAS_STD_FORMAT` to `1` or `0`.
See [full documentation of `JSON_HAS_STD_FORMAT`](../api/macros/json_has_std_format.md).
## `JSON_HAS_THREE_WAY_COMPARISON`
When the compiler and standard library support 3-way comparison (the spaceship operator `<=>`), the library provides it
for JSON values. To override the built-in check, define `JSON_HAS_THREE_WAY_COMPARISON` to `1` or `0`.
See [full documentation of `JSON_HAS_THREE_WAY_COMPARISON`](../api/macros/json_has_three_way_comparison.md).
## `JSON_NOEXCEPTION`
Exceptions can be switched off by defining the symbol `JSON_NOEXCEPTION`.
+8
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@@ -9,6 +9,13 @@ syntax that closely mimics the document being modified. Unlike [JSON Patch](json
express every kind of change (e.g., it cannot reorder array elements or remove a specific array element), but it is
easier to read and write for object-shaped documents.
!!! tip "Not a general deep merge"
A merge patch is not a general deep merge: a `#!json null` value in the patch deletes the key from the target.
To merge two objects recursively (e.g., defaults and user settings), use
[`update`](../api/basic_json/update.md) with `merge_objects` set to `#!cpp true`; see
[Merging objects](modifying_values.md#merging-objects).
??? example
The following code shows how a JSON Merge Patch is applied to a JSON document.
@@ -28,3 +35,4 @@ easier to read and write for object-shaped documents.
- [JSON Patch and Diff](json_patch.md) - a more expressive alternative that describes a sequence of operations
- [JSON Pointer](json_pointer.md) - the addressing scheme used by JSON Patch
- Function [`merge_patch`](../api/basic_json/merge_patch.md)
- Function [`update`](../api/basic_json/update.md) - merge objects, optionally recursively
+24 -6
View File
@@ -35,8 +35,12 @@ the insertion happened — useful for "add if absent" semantics.
## Merging objects
To merge one object into another, [`update`](../api/basic_json/update.md) copies all members from another object,
overwriting existing keys (similar to Python's `dict.update`). This is the idiomatic way to combine two objects.
To merge one object into another, [`update`](../api/basic_json/update.md) copies all members from another object
(similar to Python's `dict.update`). This is the idiomatic way to combine two objects. It has two modes:
- By default, the merge is shallow: existing keys are overwritten, even if both values are objects.
- With `merge_objects = #!cpp true`, keys whose values are objects in both JSON values are merged recursively.
Everything else is overwritten. In particular, arrays are replaced, not concatenated.
??? example
@@ -50,9 +54,22 @@ overwriting existing keys (similar to Python's `dict.update`). This is the idiom
--8<-- "examples/update.output"
```
For a recursive merge that follows [RFC 7386](https://tools.ietf.org/html/rfc7386), see
[JSON Merge Patch](merge_patch.md). To apply a sequence of well-defined edit operations, see
[JSON Patch](json_patch.md).
A common use of the recursive mode is combining defaults with user settings. Nested defaults that the user did not set
are kept:
```cpp
json defaults = {{"log", {{"level", "info"}, {"file", "app.log"}}}, {"retries", 3}};
json user_settings = {{"log", {{"level", "debug"}}}};
json config = defaults;
config.update(user_settings, true);
// {"log":{"file":"app.log","level":"debug"},"retries":3}
```
[JSON Merge Patch](merge_patch.md) ([RFC 7386](https://tools.ietf.org/html/rfc7386)) also merges objects recursively,
but it is a different tool: a `#!json null` in the patch means "remove this key". It is meant for applying merge patch
documents (e.g., received via HTTP PATCH). To merge configuration-like objects, use `#!cpp update(..., true)`. To apply
a sequence of well-defined edit operations, see [JSON Patch](json_patch.md).
## Removing elements
@@ -72,6 +89,7 @@ a.erase(1); // [1,3,4] (erase by index)
- [`push_back`](../api/basic_json/push_back.md) / [`emplace_back`](../api/basic_json/emplace_back.md) - append to an array
- [`emplace`](../api/basic_json/emplace.md) - insert into an object if the key is absent
- [`update`](../api/basic_json/update.md) - merge objects
- [`update`](../api/basic_json/update.md) - merge objects (shallow, or recursive with `merge_objects`)
- [`merge_patch`](../api/basic_json/merge_patch.md) - apply an RFC 7386 merge patch
- [`erase`](../api/basic_json/erase.md) / [`clear`](../api/basic_json/clear.md) - remove elements
- [JSON Patch and Diff](json_patch.md) and [JSON Merge Patch](merge_patch.md) - structured modifications
+6
View File
@@ -101,3 +101,9 @@ follows:
- Introduced inline namespace (`json_v3_11_0[_abi-tag]*`) in version 3.11.0.
- Changed structure of inline namespace in version 3.11.2.
- Added ABI tag `_dp` ([`JSON_DIAGNOSTIC_POSITIONS`](../api/macros/json_diagnostic_positions.md)) in version 3.12.0.
- Added ABI tags `_bics` ([`JSON_BRACE_INIT_COPY_SEMANTICS`](../api/macros/json_brace_init_copy_semantics.md)), `_psp`
([`JSON_PRECISE_STREAM_POSITION`](../api/macros/json_precise_stream_position.md)), `_snul`
([`JSON_STRICT_NUL_HANDLING`](../api/macros/json_strict_nul_handling.md)), `_sbu8`
([`JSON_STRICT_BINARY_UTF8`](../api/macros/json_strict_binary_utf8.md)), and `_ekmo`
([`JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS`](../api/macros/json_use_objects_for_enum_keyed_maps.md)) in version 3.13.0.
+1 -1
View File
@@ -34,7 +34,7 @@ flowchart LR
- **JSON text** is read by an [input adapter](#input-adapters), tokenized by the lexer, and turned into SAX events by
the parser.
- **Binary formats** (BJData, BSON, CBOR, MessagePack, UBJSON) are read by an input adapter and turned into the same SAX
- **Binary formats** (BJData, BON8, BSON, CBOR, MessagePack, UBJSON) are read by an input adapter and turned into the same SAX
events by the `binary_reader`.
- A [SAX consumer](#sax-interface) receives the events. The one used by [`parse`](../api/basic_json/parse.md) builds a
`basic_json` value tree.
+2 -2
View File
@@ -6,7 +6,7 @@ There are myriads of [JSON](https://json.org) libraries out there, and each may
- **Trivial integration**. Our whole code consists of a single header file [`json.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp). That's it. No library, no subproject, no dependencies, no complex build system. The class is written in vanilla C++11. All in all, everything should require no adjustment of your compiler flags or project settings.
- **Serious testing**. Our class is heavily [unit-tested](https://github.com/nlohmann/json/tree/develop/tests/src) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](http://valgrind.org) and the [Clang Sanitizers](https://clang.llvm.org/docs/index.html) that there are no memory leaks. [Google OSS-Fuzz](https://github.com/google/oss-fuzz/tree/master/projects/json) additionally runs fuzz tests against all parsers 24/7, effectively executing billions of tests so far. To maintain high quality, the project is following the [OpenSSF Best Practices](https://www.bestpractices.dev/projects/289).
- **Serious testing**. Our class is heavily [unit-tested](https://github.com/nlohmann/json/tree/develop/tests/src) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](https://valgrind.org) and the [Clang Sanitizers](https://clang.llvm.org/docs/index.html) that there are no memory leaks. [Google OSS-Fuzz](https://github.com/google/oss-fuzz/tree/master/projects/json) additionally runs fuzz tests against all parsers 24/7, effectively executing billions of tests so far. To maintain high quality, the project is following the [OpenSSF Best Practices](https://www.bestpractices.dev/projects/289).
Other aspects were not so important to us:
@@ -14,4 +14,4 @@ Other aspects were not so important to us:
- **Speed**. There are certainly [faster JSON libraries](https://github.com/miloyip/nativejson-benchmark#parsing-time) out there. However, if your goal is to speed up your development by adding JSON support with a single header, then this library is the way to go. If you know how to use a `std::vector` or `std::map`, you are already set.
See the [contribution guidelines](https://github.com/nlohmann/json/blob/master/.github/CONTRIBUTING.md#please-dont) for more information.
See the [contribution guidelines](https://github.com/nlohmann/json/blob/develop/.github/CONTRIBUTING.md#please-dont) for more information.
+13 -5
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@@ -104,7 +104,7 @@ See [documentation of `JSON_DIAGNOSTICS`](../api/macros/json_diagnostics.md) for
## Parse errors
The library throws this exception when a parse error occurs. Parse errors
can occur during the deserialization of JSON text, CBOR, MessagePack, as well
can occur during the deserialization of JSON text or of one of the binary formats (BJData, BON8, BSON, CBOR, MessagePack, UBJSON), as well
as when using JSON Patch.
Exceptions have ids 1xx.
@@ -190,7 +190,7 @@ This error indicates a syntax error while deserializing a JSON text. The error m
!!! tip
- Make sure the input is correctly read. Try to write the input to standard output to check if, for instance, the input file was successfully opened.
- Paste the input to a JSON validator like <http://jsonlint.com> or a tool like [jq](https://stedolan.github.io/jq/).
- Paste the input to a JSON validator like <https://jsonlint.com> or a tool like [jq](https://jqlang.github.io/jq/).
### json.exception.parse_error.102
@@ -278,7 +278,9 @@ In a JSON Pointer, only `~0` and `~1` are valid escape sequences.
### json.exception.parse_error.109
A JSON Pointer array index must be a number.
A JSON Pointer array index must be a number. This exception is thrown for an array index that does not begin with a
digit, except for `-` and the empty reference token, which throw [`out_of_range.404`](#jsonexceptionout_of_range404)
where they cannot be resolved.
!!! failure "Example messages"
@@ -289,6 +291,11 @@ A JSON Pointer array index must be a number.
[json.exception.parse_error.109] parse error: array index '+1' is not a number
```
!!! note
Before version 3.13.0, a one-character array index that is not a digit (e.g., `x`) threw
[`out_of_range.404`](#jsonexceptionout_of_range404) instead.
### json.exception.parse_error.110
When parsing a [binary format](../features/binary_formats/index.md), the byte vector ends before the complete value has
@@ -810,7 +817,7 @@ does not list an enumerator and it is therefore converted like the first listed
A discarded value (one created by [`parse()`](../api/basic_json/parse.md) with a callback that returns `false` for the
value, or by default-constructing a [`basic_json`](../api/basic_json/index.md) with
[`value_t::discarded`](../api/basic_json/value_t.md)) was passed to a binary serialization function, either directly or
nested in an array or object. There is no way to represent a discarded value in CBOR, MessagePack, UBJSON, BJData, or BSON.
nested in an array or object. There is no way to represent a discarded value in CBOR, MessagePack, UBJSON, BJData, BSON, or BON8.
!!! failure "Example message"
@@ -871,7 +878,8 @@ The provided key was not found in the JSON object.
### json.exception.out_of_range.404
A reference token in a JSON Pointer could not be resolved.
A reference token in a JSON Pointer could not be resolved, for instance an array index that begins with a digit but
contains other characters (e.g., `1a`), or `-` where it cannot be used.
!!! failure "Example message"
+1 -1
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@@ -26,7 +26,7 @@ Fixes bugs found in 3.11.3 and adds several features. All changes are backward-c
[BJData](../features/binary_formats/bjdata.md) draft 3 and unsigned 64-bit integers for
[BSON](../features/binary_formats/bson.md).
- Adds multidimensional C-array conversion and UTF-8 encoded `std::filesystem::path` conversions, and
lowers the minimum [CMake](../integration/cmake.md) version to allow CMake 4.0.
raises the minimum [CMake](../integration/cmake.md) version to 3.5 and supports CMake 4.0.
[Full release notes](https://github.com/nlohmann/json/releases/tag/v3.12.0).
@@ -2,8 +2,8 @@ cmake_minimum_required(VERSION 3.15)
include("cmake/HunterGate.cmake")
HunterGate(
URL "https://github.com/cpp-pm/hunter/archive/v0.23.297.tar.gz"
SHA1 "3319fe6a3b08090df7df98dee75134d68e2ef5a3"
URL "https://github.com/cpp-pm/hunter/archive/v0.26.12.tar.gz"
SHA1 "6498c5d0dec25d7fffb2b0574ebaf265179b894d"
)
project(json_example)
+28 -3
View File
@@ -2,12 +2,30 @@
# Creates a `<path>.md` sibling of each HTML output (for example,
# `features/comments/` becomes `features/comments.md`) so agents and tools can
# fetch the raw Markdown directly instead of parsing rendered HTML.
# fetch the raw Markdown directly instead of parsing rendered HTML. The
# `--8<-- "path"` lines of pymdownx.snippets are expanded with the extension's
# own preprocessor and the settings from mkdocs.yml, so the copies contain the
# included example code and files instead of the include directives.
import io
import os
import shutil
import markdown
from pymdownx.snippets import SnippetMissingError
_pages = []
_snippets = None
def on_config(config):
global _snippets
md = markdown.Markdown(
extensions=["pymdownx.snippets"],
extension_configs={"pymdownx.snippets": config["mdx_configs"].get("pymdownx.snippets", {})},
)
_snippets = md.preprocessors["snippet"]
_snippets.auto_append = [] # the glossary is only needed to render abbreviations
return config
def on_files(files, config):
@@ -22,4 +40,11 @@ def on_post_build(config):
url = file.url.rstrip("/")
target = os.path.join(site_dir, (url or "index") + ".md")
os.makedirs(os.path.dirname(target), exist_ok=True)
shutil.copyfile(file.abs_src_path, target)
with io.open(file.abs_src_path, encoding="utf-8", newline="") as source:
text = source.read()
try:
text = "\n".join(_snippets.run(text.split("\n")))
except (SnippetMissingError, OSError):
pass # keep the include directives; the regular build reports the missing file
with io.open(target, "w", encoding="utf-8", newline="") as copy:
copy.write(text)
+1 -1
View File
@@ -1,7 +1,7 @@
<!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary -->
*[ADL]: Argument-dependent lookup
*[API]: Application Programming Interfaces
*[API]: Application Programming Interface
*[ASCII]: American Standard Code for Information Interchange
*[BDFL]: Benevolent Dictator for Life
*[BJData]: Binary JData
+1
View File
@@ -299,6 +299,7 @@ nav:
- 'JSON_DISABLE_TUPLE_REFERENCE_CONVERSION': api/macros/json_disable_tuple_reference_conversion.md
- 'JSON_HAS_CPP_11, JSON_HAS_CPP_14, JSON_HAS_CPP_17, JSON_HAS_CPP_20, JSON_HAS_CPP_23, JSON_HAS_CPP_26': api/macros/json_has_cpp_11.md
- 'JSON_HAS_EXPERIMENTAL_FILESYSTEM, JSON_HAS_FILESYSTEM': api/macros/json_has_filesystem.md
- 'JSON_HAS_RANGE_VIEW_CONVERSION': api/macros/json_has_range_view_conversion.md
- 'JSON_HAS_RANGES': api/macros/json_has_ranges.md
- 'JSON_HAS_STATIC_RTTI': api/macros/json_has_static_rtti.md
- 'JSON_HAS_STD_FORMAT': api/macros/json_has_std_format.md