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Niels Lohmann a47170346a docs: new design for the documentation site (#5934 )

* docs: new design for the documentation site

Apply the brand to the Material for MkDocs site: Inter and JetBrains Mono
served by the site (upright and real italic), brand colours, blue header band
with the syntax pattern, wordmark in the header, new home page (hero, cards,
animated feature tour), 404 page, polish for tabs, search, footer, focus
rings, tables and code blocks, and theme features (code copy, previous/next
footer, TOC follow, search suggestions).

Draw the number railroad diagram, the parser callback events and the iterator
illustrations as inline SVGs that follow the light and dark scheme. The
generator scripts are in docs/mkdocs/scripts/figures; the feature slideshow
(json-light.svg, json-dark.svg, replacing json.gif on the home page) is built
by docs/mkdocs/scripts/slideshow. Decision nodes in five flowcharts become
hexagons, which need far less room.

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

* docs: add figures, table captions and a macro chooser

- Figures with numbered captions: SAX stepper, json_view layout and edit
  stepper, exception map, JSON pointer and patch walkers, QA pipeline,
  scaling and binary size charts, roadmap lanes, release timeline,
  integration decision tree and namespace builder
- Table captions (nj-table-caption) on 9 pages
- Compile times: modules and PCH charts, filesystem section, re-measured
  Figure 1, links between features/modules.md and compile_times.md
- Interactive macro chooser for features/arbitrary_types.md
- Link check: exclude URLs that answer the plugin with 400/401/419 or are
  dead (customers.md)

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

* docs: macro chooser generates adl_serializer for non-default-constructible types

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

* docs: cross-link concept pages and API pages in See also sections

Add See also links in both directions between the concept pages (features,
home, integration) and the API pages, write API links in code font, give every
entry a comment after a dash, and show the callback event figure on the parser
callbacks page.

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

* docs: address review comments on the new design

- Home: add a "Latest release" button
- Sponsors: update the list and group it by tier
- Features: list all feature pages on the index page
- Releases: add highlights per release, link the 4.0 roadmap, add the first commit to the timeline
- Exceptions: prefix all example messages with the exception name
- API: no code font for format names in the See also links of the to_/from_ pages
- Merge Patch: show the document before, the patch, and the result
- Replace "--" with typographic dashes, mark external links with an icon, center Mermaid diagrams

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

---------

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

2026-10-27 07:41:42 +01:00

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JSON_CATCH_USER, JSON_THROW_USER, JSON_TRY_USER

// (1)
#define JSON_CATCH_USER(exception) /* value */
// (2)
#define JSON_THROW_USER(exception) /* value */
// (3)
#define JSON_TRY_USER /* value */

Controls how exceptions are handled by the library.

This macro overrides #!cpp catch calls inside the library. The argument is the type of the exception to catch. The library uses it in a single place: to swallow any exception escaping the parent-pointer check that JSON_DIAGNOSTICS adds to the class invariant. The places where the library catches its own json::out_of_range exceptions use JSON_INTERNAL_CATCH instead, which JSON_CATCH_USER also overrides unless JSON_INTERNAL_CATCH_USER is defined. The macro is always followed by a scope.
This macro overrides #!cpp throw calls inside the library. The argument is the exception to be thrown. Note that JSON_THROW_USER should leave the current scope (e.g., by throwing or aborting), as continuing after it may yield undefined behavior.
This macro overrides #!cpp try calls inside the library. It has no arguments and is always followed by a scope.

Parameters

exception (in): an exception type

Default definition

By default, the macros map to their respective C++ keywords:

#define JSON_CATCH_USER(exception) catch(exception)
#define JSON_THROW_USER(exception) throw exception
#define JSON_TRY_USER              try

When exceptions are switched off, the #!cpp try block is executed unconditionally, and throwing exceptions is replaced by calling std::abort to make reaching the #!cpp throw branch abort the process.

#define JSON_THROW_USER(exception) std::abort()
#define JSON_TRY_USER              if (true)
#define JSON_CATCH_USER(exception) if (false)

Examples

??? example

The code below switches off exceptions and creates a log entry with a detailed error message in case of errors.

```cpp
#include <iostream>

#define JSON_TRY_USER if(true)
#define JSON_CATCH_USER(exception) if(false)
#define JSON_THROW_USER(exception)                           \
    {std::clog << "Error in " << __FILE__ << ":" << __LINE__ \
               << " (function " << __FUNCTION__ << ") - "    \
               << (exception).what() << std::endl;           \
     std::abort();}

#include <nlohmann/json.hpp>
```

Version history

Added in version 3.1.0.

3.1 KiB Raw Blame History