Niels Lohmann
63c10a51fc
* 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>
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Comments
This library does not support comments by default. It does so for three reasons:
-
Comments are not part of the JSON specification. You may argue that
//or/* */are allowed in JavaScript, but JSON is not JavaScript. -
This was not an oversight: Douglas Crockford wrote on this in May 2012:
I removed comments from JSON because I saw people were using them to hold parsing directives, a practice which would have destroyed interoperability. I know that the lack of comments makes some people sad, but it shouldn't.
Suppose you are using JSON to keep configuration files, which you would like to annotate. Go ahead and insert all the comments you like. Then pipe it through JSMin before handing it to your JSON parser.
-
It is dangerous for interoperability if some libraries add comment support while others do not. Please check The Harmful Consequences of the Robustness Principle on this.
However, you can set parameter ignore_comments to #!cpp true in the parse function to ignore // or /* */ comments. Comments will then be treated as whitespace. Combined with ignore_trailing_commas (also a parse parameter), this covers what is commonly referred to as JSONC (JSON with Comments, as used e.g. by Visual Studio Code's .jsonc files) -- comments and trailing commas, nothing more. This is a different, smaller extension than JSON5, which additionally allows unquoted keys, single-quoted strings, and other syntax changes that this library does not support.
For more information, see JSON With Commas and Comments (JWCC).
!!! example
Consider the following JSON with comments.
```json
{
// update in 2006: removed Pluto
"planets": ["Mercury", "Venus", "Earth", "Mars",
"Jupiter", "Uranus", "Neptune" /*, "Pluto" */]
}
```
When calling `parse` without additional argument, a parse error exception is thrown. If `ignore_comments` is set to `#!cpp true`, the comments are ignored during parsing:
```cpp
--8<-- "examples/comments.cpp"
```
Output:
```
--8<-- "examples/comments.output"
```