Merge branch 'develop' into claude/3453-breaking-change-flags-c937b4

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Add JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON to the 4.0 example
2026-09-29 03:00:31 +00:00 · 2026-09-28 22:22:39 +02:00 · 2026-09-28 18:47:31 +02:00 · 2026-09-27 20:58:00 +02:00 · 2026-09-27 16:55:18 +02:00 · 2026-09-27 16:51:39 +02:00
25 changed files with 211 additions and 499 deletions
@@ -67,7 +67,6 @@ jobs:

          python3 $TOOL_DIR/amalgamate.py -c $TOOL_DIR/config_json.json -s .
          python3 $TOOL_DIR/amalgamate.py -c $TOOL_DIR/config_json_fwd.json -s .
-          cp include/nlohmann/json_literals.hpp $INCLUDE_DIR/json_literals.hpp

          # the header list of the Bazel "json" target must match the files in include/
          cmake -P cmake/scripts/gen_bazel_build_file.cmake
@@ -65,7 +65,6 @@ cc_library(
        "include/nlohmann/detail/value_t.hpp",
        "include/nlohmann/json.hpp",
        "include/nlohmann/json_fwd.hpp",
-        "include/nlohmann/json_literals.hpp",
        "include/nlohmann/ordered_map.hpp",
        "include/nlohmann/thirdparty/hedley/hedley.hpp",
        "include/nlohmann/thirdparty/hedley/hedley_undef.hpp",
@@ -21,8 +21,6 @@ TESTS_SRCS=$(shell find tests -type f \( -name '*.hpp' -o -name '*.cpp' -o -name
 # the single headers (amalgamated from the source files)
 AMALGAMATED_FILE=single_include/nlohmann/json.hpp
 AMALGAMATED_FWD_FILE=single_include/nlohmann/json_fwd.hpp
-# json_literals.hpp only includes <nlohmann/json.hpp>, so it is copied verbatim
-AMALGAMATED_LITERALS_FILE=single_include/nlohmann/json_literals.hpp


 ##########################################################################
@@ -31,7 +29,7 @@ AMALGAMATED_LITERALS_FILE=single_include/nlohmann/json_literals.hpp

 # main target
 all:
-	@echo "amalgamate - amalgamate files single_include/nlohmann/json{,_fwd,_literals}.hpp from the include/nlohmann sources"
+	@echo "amalgamate - amalgamate files single_include/nlohmann/json{,_fwd}.hpp from the include/nlohmann sources"
 	@echo "BUILD.bazel - regenerate the Bazel BUILD file from the include/nlohmann sources"
 	@echo "ChangeLog.md - generate ChangeLog file"
 	@echo "check-amalgamation - check whether sources have been amalgamated and BUILD.bazel is up to date"
@@ -156,14 +154,14 @@ install_astyle:

 # call the Artistic Style pretty printer on all source files
 pretty: install_astyle
-	$(ASTYLE) --project=tools/astyle/.astylerc $(SRCS) $(TESTS_SRCS) $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_LITERALS_FILE) docs/mkdocs/docs/examples/*.cpp
+	$(ASTYLE) --project=tools/astyle/.astylerc $(SRCS) $(TESTS_SRCS) $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) docs/mkdocs/docs/examples/*.cpp

 # call the Clang-Format on all source files
 pretty_format:
 	for FILE in $(SRCS) $(TESTS_SRCS) $(AMALGAMATED_FILE) docs/mkdocs/docs/examples/*.cpp; do echo $$FILE; clang-format -i $$FILE; done

 # create single header files and pretty print
-amalgamate: $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_LITERALS_FILE)
+amalgamate: $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE)
 	$(MAKE) pretty

 # call the amalgamation tool for json.hpp
@@ -174,23 +172,16 @@ $(AMALGAMATED_FILE): $(SRCS)
 $(AMALGAMATED_FWD_FILE): $(SRCS)
 	tools/amalgamate/amalgamate.py -c tools/amalgamate/config_json_fwd.json -s . --verbose=yes

-# copy json_literals.hpp
-$(AMALGAMATED_LITERALS_FILE): include/nlohmann/json_literals.hpp
-	cp include/nlohmann/json_literals.hpp $(AMALGAMATED_LITERALS_FILE)
-
 # check if file single_include/nlohmann/json.hpp has been amalgamated from the nlohmann sources
 # Note: this target is called by Travis
 check-amalgamation:
 	@mv $(AMALGAMATED_FILE) $(AMALGAMATED_FILE)~
 	@mv $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_FWD_FILE)~
-	@mv $(AMALGAMATED_LITERALS_FILE) $(AMALGAMATED_LITERALS_FILE)~
 	@$(MAKE) amalgamate
 	@diff $(AMALGAMATED_FILE) $(AMALGAMATED_FILE)~ || (echo "===================================================================\n  Amalgamation required! Please read the contribution guidelines\n  in file .github/CONTRIBUTING.md.\n===================================================================" ; mv $(AMALGAMATED_FILE)~ $(AMALGAMATED_FILE) ; false)
 	@diff $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_FWD_FILE)~ || (echo "===================================================================\n  Amalgamation required! Please read the contribution guidelines\n  in file .github/CONTRIBUTING.md.\n===================================================================" ; mv $(AMALGAMATED_FWD_FILE)~ $(AMALGAMATED_FWD_FILE) ; false)
-	@diff $(AMALGAMATED_LITERALS_FILE) $(AMALGAMATED_LITERALS_FILE)~ || (echo "===================================================================\n  Amalgamation required! Please read the contribution guidelines\n  in file .github/CONTRIBUTING.md.\n===================================================================" ; mv $(AMALGAMATED_LITERALS_FILE)~ $(AMALGAMATED_LITERALS_FILE) ; false)
 	@mv $(AMALGAMATED_FILE)~ $(AMALGAMATED_FILE)
 	@mv $(AMALGAMATED_FWD_FILE)~ $(AMALGAMATED_FWD_FILE)
-	@mv $(AMALGAMATED_LITERALS_FILE)~ $(AMALGAMATED_LITERALS_FILE)
 	@mv BUILD.bazel BUILD.bazel~
 	@$(MAKE) BUILD.bazel
 	@diff BUILD.bazel BUILD.bazel~ || (echo "===================================================================\n  BUILD.bazel is out of date! Please run 'make BUILD.bazel'.\n===================================================================" ; mv BUILD.bazel~ BUILD.bazel ; false)
@@ -231,7 +222,7 @@ json.tar.xz:
 # We use `-X` to make the resulting ZIP file reproducible, see
 # <https://content.pivotal.io/blog/barriers-to-deterministic-reproducible-zip-files>.
 include.zip: BUILD.bazel
-	zip -9 --recurse-paths -X include.zip $(SRCS) $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) $(AMALGAMATED_LITERALS_FILE) BUILD.bazel MODULE.bazel meson.build LICENSE.MIT
+	zip -9 --recurse-paths -X include.zip $(SRCS) $(AMALGAMATED_FILE) $(AMALGAMATED_FWD_FILE) BUILD.bazel MODULE.bazel meson.build LICENSE.MIT

 # Create the files for a release and add signatures and hashes.
 release: include.zip json.tar.xz
@@ -240,12 +231,10 @@ release: include.zip json.tar.xz
 	gpg --armor --detach-sig include.zip
 	gpg --armor --detach-sig $(AMALGAMATED_FILE)
 	gpg --armor --detach-sig $(AMALGAMATED_FWD_FILE)
-	gpg --armor --detach-sig $(AMALGAMATED_LITERALS_FILE)
 	gpg --armor --detach-sig json.tar.xz
 	cp $(AMALGAMATED_FILE) release_files
 	cp $(AMALGAMATED_FWD_FILE) release_files
-	cp $(AMALGAMATED_LITERALS_FILE) release_files
-	mv $(AMALGAMATED_FILE).asc $(AMALGAMATED_FWD_FILE).asc $(AMALGAMATED_LITERALS_FILE).asc json.tar.xz json.tar.xz.asc include.zip include.zip.asc release_files
+	mv $(AMALGAMATED_FILE).asc $(AMALGAMATED_FWD_FILE).asc json.tar.xz json.tar.xz.asc include.zip include.zip.asc release_files
 	cd release_files ; shasum -a 256 json.hpp include.zip json.tar.xz > hashes.txt


@@ -373,10 +373,9 @@ file(GLOB_RECURSE INDENT_FILES
 set(include_dir ${PROJECT_SOURCE_DIR}/single_include/nlohmann)
 set(tool_dir ${PROJECT_SOURCE_DIR}/tools/amalgamate)
 add_custom_target(ci_test_amalgamation
-    COMMAND rm -fr ${include_dir}/json.hpp~ ${include_dir}/json_fwd.hpp~ ${include_dir}/json_literals.hpp~
+    COMMAND rm -fr ${include_dir}/json.hpp~ ${include_dir}/json_fwd.hpp~
    COMMAND cp ${include_dir}/json.hpp ${include_dir}/json.hpp~
    COMMAND cp ${include_dir}/json_fwd.hpp ${include_dir}/json_fwd.hpp~
-    COMMAND cp ${include_dir}/json_literals.hpp ${include_dir}/json_literals.hpp~

    COMMAND ${Python3_EXECUTABLE} -mvenv venv_astyle
    COMMAND venv_astyle/bin/pip3 --quiet install -r ${CMAKE_SOURCE_DIR}/tools/astyle/requirements.txt
@@ -384,12 +383,10 @@ add_custom_target(ci_test_amalgamation

    COMMAND ${Python3_EXECUTABLE} ${tool_dir}/amalgamate.py -c ${tool_dir}/config_json.json -s .
    COMMAND ${Python3_EXECUTABLE} ${tool_dir}/amalgamate.py -c ${tool_dir}/config_json_fwd.json -s .
-    COMMAND cp ${PROJECT_SOURCE_DIR}/include/nlohmann/json_literals.hpp ${include_dir}/json_literals.hpp
    COMMAND venv_astyle/bin/astyle --project=tools/astyle/.astylerc --suffix=none ${include_dir}/json.hpp ${include_dir}/json_fwd.hpp

    COMMAND diff ${include_dir}/json.hpp~ ${include_dir}/json.hpp
    COMMAND diff ${include_dir}/json_fwd.hpp~ ${include_dir}/json_fwd.hpp
-    COMMAND diff ${include_dir}/json_literals.hpp~ ${include_dir}/json_literals.hpp

    COMMAND venv_astyle/bin/astyle --project=tools/astyle/.astylerc --suffix=orig ${INDENT_FILES}
    COMMAND for FILE in `find . -name '*.orig'`\; do false \; done
@@ -28,7 +28,6 @@ header. See also the [macro overview page](../../features/macros.md).
 - [**JSON_HAS_RANGES**](json_has_ranges.md) - control `std::ranges` support
 - [**JSON_HAS_STD_FORMAT**](json_has_std_format.md) - control `std::format`/`std::formatter` support
 - [**JSON_HAS_THREE_WAY_COMPARISON**](json_has_three_way_comparison.md) - control 3-way comparison support
- [**JSON_NO_AUTOMATIC_UDLS**](json_no_automatic_udls.md) - do not include the user-defined string literals (UDLs) automatically
 - [**JSON_NO_IO**](json_no_io.md) - switch off functions relying on certain C++ I/O headers
 - [**JSON_NO_THREAD_LOCAL**](json_no_thread_local.md) - switch off the use of `thread_local` storage
 - [**JSON_SKIP_UNSUPPORTED_COMPILER_CHECK**](json_skip_unsupported_compiler_check.md) - do not warn about unsupported compilers
@@ -115,3 +115,4 @@ The default value is `0` (disabled — existing behavior is preserved).
 ## Version history

 - Added in version 3.13.0.
+- Planned to become the default (with the macro removed) in version 4.0.0.
@@ -1,68 +0,0 @@
-# JSON_NO_AUTOMATIC_UDLS
-
-```cpp
-#define JSON_NO_AUTOMATIC_UDLS
-```
-
-When defined, `<nlohmann/json.hpp>` does not include `<nlohmann/json_literals.hpp>`, so the user-defined string
-literals [`operator""_json`](../operator_literal_json.md) and
-[`operator""_json_pointer`](../operator_literal_json_pointer.md) are not declared. Include
-`<nlohmann/json_literals.hpp>` in the files that use them.
-
-The literals are ordinary inline functions whose bodies call the parser, so every translation unit that includes them
-instantiates the parser — even if it never parses anything itself. Defining `JSON_NO_AUTOMATIC_UDLS` for a whole project
-avoids this cost in translation units that do not parse (e.g., ones that only define types and conversions or pass
-`json` values around) and reduces their compile time.
-
-## Default definition
-
-By default, `#!cpp JSON_NO_AUTOMATIC_UDLS` is not defined, and `<nlohmann/json.hpp>` includes
-`<nlohmann/json_literals.hpp>`.
-
-```cpp
-#undef JSON_NO_AUTOMATIC_UDLS
-```
-
-## Notes
-
-!!! info "Header `<nlohmann/json_literals.hpp>`"
-
-    The header includes `<nlohmann/json.hpp>` itself and places the literals according to
-    [`JSON_USE_GLOBAL_UDLS`](json_use_global_udls.md). It is part of the multi-header sources (`include/nlohmann`)
-    and of the single-header sources (`single_include/nlohmann`), next to `json.hpp`.
-
-!!! info "C++ modules"
-
-    The `nlohmann.json` [module](../../features/modules.md) always exports the literals, regardless of this macro.
-
-## Examples
-
-??? example
-
-    The code below includes the library without the literals and adds them in a single translation unit.
-
-    ```cpp
-    // compiled with -DJSON_NO_AUTOMATIC_UDLS for the whole project
-    #include <nlohmann/json.hpp>
-
-    // this file uses the literals, so it includes them explicitly
-    #include <nlohmann/json_literals.hpp>
-
-    int main()
-    {
-        auto j = R"({"foo": 42})"_json;
-        return j.at("/foo"_json_pointer) == 42 ? 0 : 1;
-    }
-    ```
-
-    Without the include of `<nlohmann/json_literals.hpp>`, the code would fail to compile.
-
-## See also
-
- [`operator""_json`](../operator_literal_json.md)
- [`operator""_json_pointer`](../operator_literal_json_pointer.md)
- [`JSON_USE_GLOBAL_UDLS`](json_use_global_udls.md) - place user-defined string literals (UDLs) into the global namespace
-
-## Version history
-
- Added in version 3.13.0.
@@ -15,7 +15,7 @@ The default value is `1`.
 #define JSON_USE_GLOBAL_UDLS 1
 ```

-When the macro is not defined, the library behaves as if it were defined to its default value.
+When the macro is not defined, the library will define it to its default value.

 ## Notes

@@ -32,11 +32,6 @@ When the macro is not defined, the library behaves as if it were defined to its
    [`JSON_GlobalUDLs`](../../integration/cmake.md#json_globaludls) (`ON` by default) which defines
    `JSON_USE_GLOBAL_UDLS` accordingly.

-!!! info "Leaving out the literals"
-
-    If [`JSON_NO_AUTOMATIC_UDLS`](json_no_automatic_udls.md) is defined, the literals are only declared where
-    `<nlohmann/json_literals.hpp>` is included; this macro then applies to that header.
-
 ## Examples

 ??? example "Example 1: Default behavior"
@@ -97,7 +92,6 @@ When the macro is not defined, the library behaves as if it were defined to its

 - [`operator""_json`](../operator_literal_json.md)
 - [`operator""_json_pointer`](../operator_literal_json_pointer.md)
- [`JSON_NO_AUTOMATIC_UDLS`](json_no_automatic_udls.md) - do not include the user-defined string literals automatically
 - [:simple-cmake: JSON_GlobalUDLs](../../integration/cmake.md#json_globaludls) - CMake option to control the macro

 ## Version history
@@ -18,9 +18,7 @@ using namespace nlohmann;
 ```

 This is suggested to ease migration to the next major version release of the library. See
-[`JSON_USE_GLOBAL_UDLS`](macros/json_use_global_udls.md#notes) for details. The operator is declared in header
-`<nlohmann/json_literals.hpp>`, which `<nlohmann/json.hpp>` includes unless
-[`JSON_NO_AUTOMATIC_UDLS`](macros/json_no_automatic_udls.md) is defined.
+[`JSON_USE_GLOBAL_UDLS`](macros/json_use_global_udls.md#notes) for details.

 ## Parameters

@@ -61,8 +59,6 @@ Linear.
 ## See also

 - [Creating JSON values](../features/creating_values.md) - the article on creating JSON values
- [JSON_NO_AUTOMATIC_UDLS](macros/json_no_automatic_udls.md) - do not include the user-defined string literals
-  automatically

 ## Version history

@@ -17,9 +17,7 @@ using namespace nlohmann::literals::json_literals;
 using namespace nlohmann;
 ```
 This is suggested to ease migration to the next major version release of the library. See
-[`JSON_USE_GLOBAL_UDLS`](macros/json_use_global_udls.md#notes) for details. The operator is declared in header
-`<nlohmann/json_literals.hpp>`, which `<nlohmann/json.hpp>` includes unless
-[`JSON_NO_AUTOMATIC_UDLS`](macros/json_no_automatic_udls.md) is defined.
+[`JSON_USE_GLOBAL_UDLS`](macros/json_use_global_udls.md#notes) for details.

 ## Parameters

@@ -60,8 +58,6 @@ Linear.
 ## See also

 - [json_pointer](json_pointer/index.md) - type to represent JSON Pointers
- [JSON_NO_AUTOMATIC_UDLS](macros/json_no_automatic_udls.md) - do not include the user-defined string literals
-  automatically

 ## Version history

@@ -14,7 +14,7 @@ work items are tracked in the [GitHub milestones](https://github.com/nlohmann/js
  opt-in.
 - **Keep the 3.x public API stable.** Releases follow [semantic versioning](https://semver.org). Changes that would
  break existing code are only added behind a feature macro, so users can opt in and test their code before a next
-  major release.
+  major release, see [Version 4.0](#version-40).
 - **Support a broad range of compilers and platforms.** The [CI](quality_assurance.md) keeps testing old and new
  versions of GCC, Clang, MSVC, and other compilers on Linux, macOS, and Windows.
 - **Keep the quality assurance up.** Every change keeps the test coverage at 100%, passes the static and dynamic
@@ -37,7 +37,65 @@ work items are tracked in the [GitHub milestones](https://github.com/nlohmann/js

 ## Version 4.0

-There is no decision yet on whether or when a version 4.0 with breaking changes will be released. Proposals that need
-a major version, for instance stricter type conversions, are collected in issue
-[#3453](https://github.com/nlohmann/json/issues/3453). Until then, such changes are only added as opt-in behavior
-behind feature macros.
+There is no release date for version 4.0 yet. Proposals that need a major version, for instance stricter type
+conversions, are collected in issue [#3453](https://github.com/nlohmann/json/issues/3453).
+
+!!! note "Not final"
+
+    The plan for version 4.0 described below is not final and may still change: macros may be added to or removed from
+    the list, and planned defaults may be revised. Any such change will be documented on this page.
+
+### Trying out 4.0 today
+
+Version 4.0 will not be developed on a separate branch. Instead, every breaking change is first added to a 3.x release
+behind a macro whose default keeps the 3.x behavior. Version 4.0 then switches the defaults and removes the macros.
+Version 4.0 is therefore the sum of these macros: you can try it on the 3.x release train today by defining each macro
+to its 4.0 value and fixing what no longer compiles or behaves differently. Once your code works with all of them, it
+is ready for version 4.0.
+
+The following macros guard changes that are planned to become the default in version 4.0:
+
+| Macro                                                                                                            | 3.x default | 4.0 behavior                                                                                                                  | CMake option                                                                                                       | Added  |
+|------------------------------------------------------------------------------------------------------------------|-------------|-------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------|--------|
+| [`JSON_USE_IMPLICIT_CONVERSIONS`](../api/macros/json_use_implicit_conversions.md)                                | `1`         | `0`: no implicit conversions from `basic_json` to other types; use [`get`](../api/basic_json/get.md) instead                  | [`JSON_ImplicitConversions`](../integration/cmake.md#json_implicitconversions)                                     | 3.9.0  |
+| [`JSON_USE_GLOBAL_UDLS`](../api/macros/json_use_global_udls.md)                                                  | `1`         | `0`: the string literals `_json` and `_json_pointer` are only available in namespace `nlohmann::literals`                    | [`JSON_GlobalUDLs`](../integration/cmake.md#json_globaludls)                                                       | 3.11.0 |
+| [`JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON`](../api/macros/json_use_legacy_discarded_value_comparison.md)      | `0`         | removed: the deprecated legacy comparison of discarded values can no longer be enabled                                        | [`JSON_LegacyDiscardedValueComparison`](../integration/cmake.md#json_legacydiscardedvaluecomparison)               | 3.11.0 |
+| [`JSON_BRACE_INIT_COPY_SEMANTICS`](../api/macros/json_brace_init_copy_semantics.md)                              | `0`         | `1`: single-element brace initialization such as `#!cpp json j{obj};` copies the element instead of creating an array         | –                                                                                                                  | 3.13.0 |
+| [`JSON_PRECISE_STREAM_POSITION`](../api/macros/json_precise_stream_position.md)                                  | `0`         | `1`: reading from a stream does not consume the character after a number                                                      | –                                                                                                                  | 3.13.0 |
+| [`JSON_STRICT_NUL_HANDLING`](../api/macros/json_strict_nul_handling.md)                                          | `0`         | `1`: a NUL byte in the input is a parse error instead of the end of input                                                     | [`JSON_StrictNulHandling`](../integration/cmake.md#json_strictnulhandling)                                         | 3.13.0 |
+
+For example, the following makes a 3.x release behave like version 4.0 with respect to these changes:
+
+```cpp
+#define JSON_USE_IMPLICIT_CONVERSIONS 0
+#define JSON_USE_GLOBAL_UDLS 0
+#define JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON 0
+#define JSON_BRACE_INIT_COPY_SEMANTICS 1
+#define JSON_PRECISE_STREAM_POSITION 1
+#define JSON_STRICT_NUL_HANDLING 1
+#include <nlohmann/json.hpp>
+```
+
+The macros must be defined before the library header is included; setting them once in the build system is the easiest
+way to achieve this.
+
+### Removal of deprecated functions
+
+Version 4.0 will remove all deprecated functions. Compiling with deprecation warnings enabled shows which of them your
+code still uses. The [migration guide](../integration/migration_guide.md#replace-deprecated-functions) shows how to
+replace each of them.
+
+| Deprecated                                                                                                                                                                                                                                         | Since  | Migration                                                                        |
+|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------|----------------------------------------------------------------------------------|
+| `#!cpp operator<<(basic_json&, std::istream&)`                                                                                                                                                                                                     | 3.0.0  | [Parsing](../integration/migration_guide.md#parsing)                             |
+| `#!cpp operator>>(const basic_json&, std::ostream&)`                                                                                                                                                                                               | 3.0.0  | [Miscellaneous functions](../integration/migration_guide.md#miscellaneous-functions) |
+| `iterator_wrapper`                                                                                                                                                                                                                                 | 3.1.0  | [Miscellaneous functions](../integration/migration_guide.md#miscellaneous-functions) |
+| [`parse`](../api/basic_json/parse.md), [`accept`](../api/basic_json/accept.md), and [`sax_parse`](../api/basic_json/sax_parse.md) with an initializer list `{ptr, len}` or `{first, last}`                                                         | 3.8.0  | [Parsing](../integration/migration_guide.md#parsing)                             |
+| [`from_bson`](../api/basic_json/from_bson.md), [`from_cbor`](../api/basic_json/from_cbor.md), [`from_msgpack`](../api/basic_json/from_msgpack.md), and [`from_ubjson`](../api/basic_json/from_ubjson.md) with `(ptr, len)` or an initializer list | 3.8.0  | [Parsing](../integration/migration_guide.md#parsing)                             |
+| [`json_pointer::operator string_t`](../api/json_pointer/operator_string_t.md)                                                                                                                                                                      | 3.11.0 | [JSON Pointers](../integration/migration_guide.md#json-pointers)                 |
+| [`json_pointer`](../api/json_pointer/index.md) with a `basic_json` type as template argument, and the overloads of `value`, `contains`, `operator[]`, and `at` accepting such a pointer                                                           | 3.11.0 | [JSON Pointers](../integration/migration_guide.md#json-pointers)                 |
+| Comparing a [`json_pointer`](../api/json_pointer/index.md) with a string via [`operator==`](../api/json_pointer/operator_eq.md) or [`operator!=`](../api/json_pointer/operator_ne.md)                                                              | 3.11.2 | [JSON Pointers](../integration/migration_guide.md#json-pointers)                 |
+
+The deprecated legacy comparison of discarded values is controlled by a macro and therefore listed in the table above.
+
+New breaking changes will follow the same path: they are added to these tables when they land in a 3.x release.
@@ -83,15 +83,6 @@ When defined, default parse and serialize functions for enums are excluded and h

 See [full documentation of `JSON_DISABLE_ENUM_SERIALIZATION`](../api/macros/json_disable_enum_serialization.md).

-## `JSON_NO_AUTOMATIC_UDLS`
-
-When defined, `<nlohmann/json.hpp>` does not include `<nlohmann/json_literals.hpp>` with the user-defined string literals
-`operator""_json` and `operator""_json_pointer`. This reduces the compile time of translation units that do not use
-them, because the literals instantiate the parser in every translation unit that includes them. Include
-`<nlohmann/json_literals.hpp>` where the literals are needed.
-
-See [full documentation of `JSON_NO_AUTOMATIC_UDLS`](../api/macros/json_no_automatic_udls.md).
-
 ## `JSON_NO_IO`

 When defined, headers `<cstdio>`, `<ios>`, `<iosfwd>`, `<istream>`, and `<ostream>` are not included and parse functions
@@ -40,9 +40,6 @@ Only the following symbols are exported from `nlohmann.json`:
 - `nlohmann::literals::json_literals::operator""_json`
 - `nlohmann::literals::json_literals::operator""_json_pointer`

-The module always exports the two user-defined string literals, even if
-[`JSON_NO_AUTOMATIC_UDLS`](../api/macros/json_no_automatic_udls.md) is defined when building it.
-
 Additionally, the following `nlohmann::detail` symbols are exported, solely to work around an MSVC compilation issue
 ([#3970](https://github.com/nlohmann/json/issues/3970)). They are implementation details, not part of the public API,
 and should not be used directly:
@@ -15,7 +15,4 @@ Clang).

 You can further use file
 [`single_include/nlohmann/json_fwd.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json_fwd.hpp)
-for forward declarations, and file
-[`single_include/nlohmann/json_literals.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json_literals.hpp)
-for the user-defined string literals if you define
-[`JSON_NO_AUTOMATIC_UDLS`](../api/macros/json_no_automatic_udls.md).
+for forward declarations.
@@ -1,10 +1,13 @@
 # Migration Guide

 This page collects some guidelines on how to future-proof your code for future versions of this library.
+The [roadmap](../community/roadmap.md#version-40) lists what will change in version 4.0, including the macros that let
+you try its behavior with a 3.x release; this page describes how to adjust your code.

 ## Replace deprecated functions

-The following functions have been deprecated and will be removed in the next major version (i.e., 4.0.0). All
+The following functions have been deprecated and will be removed in the next major version (i.e., 4.0.0), see the
+[roadmap](../community/roadmap.md#removal-of-deprecated-functions) for an overview. All
 deprecations are annotated with
 [`HEDLEY_DEPRECATED_FOR`](https://nemequ.github.io/hedley/api-reference.html#HEDLEY_DEPRECATED_FOR) to report which
 function to use instead.
@@ -34,8 +37,9 @@ function to use instead.
  [`accept`](../api/basic_json/accept.md), [`sax_parse`](../api/basic_json/sax_parse.md),
  [`from_cbor`](../api/basic_json/from_cbor.md), [`from_msgpack`](../api/basic_json/from_msgpack.md),
  [`from_ubjson`](../api/basic_json/from_ubjson.md), and [`from_bson`](../api/basic_json/from_bson.md) via initializer
-  lists is deprecated since 3.8.0. Instead, pass two iterators; for instance, call `from_cbor(ptr, ptr+len)` instead of
-  `from_cbor({ptr, len})`.
+  lists is deprecated since 3.8.0. The same holds for passing a pointer and a length as two arguments to the `from_*`
+  functions. Instead, pass two iterators; for instance, call `from_cbor(ptr, ptr+len)` instead of
+  `from_cbor({ptr, len})` or `from_cbor(ptr, len)`.

    === "Deprecated"
  
@@ -293,7 +293,6 @@ nav:
          - 'JSON_HAS_STATIC_RTTI': api/macros/json_has_static_rtti.md
          - 'JSON_HAS_STD_FORMAT': api/macros/json_has_std_format.md
          - 'JSON_HAS_THREE_WAY_COMPARISON': api/macros/json_has_three_way_comparison.md
-          - 'JSON_NO_AUTOMATIC_UDLS': api/macros/json_no_automatic_udls.md
          - 'JSON_NOEXCEPTION': api/macros/json_noexception.md
          - 'JSON_NO_IO': api/macros/json_no_io.md
          - 'JSON_NO_THREAD_LOCAL': api/macros/json_no_thread_local.md
@@ -915,3 +915,7 @@ void templated_json_throw(ExceptionType exception)
 #ifndef JSON_DISABLE_ENUM_SERIALIZATION
    #define JSON_DISABLE_ENUM_SERIALIZATION 0
 #endif
+
+#ifndef JSON_USE_GLOBAL_UDLS
+    #define JSON_USE_GLOBAL_UDLS 1
+#endif
@@ -25,6 +25,7 @@
 #undef JSON_INLINE_VARIABLE
 #undef JSON_NO_UNIQUE_ADDRESS
 #undef JSON_DISABLE_ENUM_SERIALIZATION
+#undef JSON_USE_GLOBAL_UDLS

 #ifndef JSON_TEST_KEEP_MACROS
    #undef JSON_CATCH
@@ -6423,6 +6423,55 @@ std::string format_as(const NLOHMANN_BASIC_JSON_TPL& j)
    return j.dump();
 }

+inline namespace literals
+{
+inline namespace json_literals
+{
+
+/// @brief user-defined string literal for JSON values
+/// @sa https://json.nlohmann.me/api/basic_json/operator_literal_json/
+JSON_HEDLEY_NON_NULL(1)
+#if !defined(JSON_HEDLEY_GCC_VERSION) || JSON_HEDLEY_GCC_VERSION_CHECK(4,9,0)
+    inline nlohmann::json operator""_json(const char* s, std::size_t n)
+#else
+    // GCC 4.8 requires a space between "" and suffix
+    inline nlohmann::json operator"" _json(const char* s, std::size_t n)
+#endif
+{
+    return nlohmann::json::parse(s, s + n);
+}
+
+#if defined(__cpp_char8_t)
+JSON_HEDLEY_NON_NULL(1)
+inline nlohmann::json operator""_json(const char8_t* s, std::size_t n)
+{
+    return nlohmann::json::parse(reinterpret_cast<const char*>(s),
+                                 reinterpret_cast<const char*>(s) + n);
+}
+#endif
+
+/// @brief user-defined string literal for JSON pointer
+/// @sa https://json.nlohmann.me/api/basic_json/operator_literal_json_pointer/
+JSON_HEDLEY_NON_NULL(1)
+#if !defined(JSON_HEDLEY_GCC_VERSION) || JSON_HEDLEY_GCC_VERSION_CHECK(4,9,0)
+    inline nlohmann::json::json_pointer operator""_json_pointer(const char* s, std::size_t n)
+#else
+    // GCC 4.8 requires a space between "" and suffix
+    inline nlohmann::json::json_pointer operator"" _json_pointer(const char* s, std::size_t n)
+#endif
+{
+    return nlohmann::json::json_pointer(std::string(s, n));
+}
+
+#if defined(__cpp_char8_t)
+inline nlohmann::json::json_pointer operator""_json_pointer(const char8_t* s, std::size_t n)
+{
+    return nlohmann::json::json_pointer(std::string(reinterpret_cast<const char*>(s), n));
+}
+#endif
+
+}  // namespace json_literals
+}  // namespace literals
 NLOHMANN_JSON_NAMESPACE_END

 ///////////////////////
@@ -6557,6 +6606,17 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c

 }  // namespace std

+#if JSON_USE_GLOBAL_UDLS
+    #if !defined(JSON_HEDLEY_GCC_VERSION) || JSON_HEDLEY_GCC_VERSION_CHECK(4,9,0)
+        using nlohmann::literals::json_literals::operator""_json; // NOLINT(misc-unused-using-decls,google-global-names-in-headers)
+        using nlohmann::literals::json_literals::operator""_json_pointer; //NOLINT(misc-unused-using-decls,google-global-names-in-headers)
+    #else
+        // GCC 4.8 requires a space between "" and suffix
+        using nlohmann::literals::json_literals::operator"" _json; // NOLINT(misc-unused-using-decls,google-global-names-in-headers)
+        using nlohmann::literals::json_literals::operator"" _json_pointer; //NOLINT(misc-unused-using-decls,google-global-names-in-headers)
+    #endif
+#endif
+
 #include <nlohmann/detail/macro_unscope.hpp>

 // End of GCC diagnostic pragmas for C++ modules support
@@ -6564,12 +6624,4 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
    #pragma GCC diagnostic pop
 #endif

-// The user-defined string literals are in a separate header, because their
-// bodies instantiate the parser in every translation unit that includes them.
-// Define JSON_NO_AUTOMATIC_UDLS to include <nlohmann/json_literals.hpp> only
-// where needed.
-#ifndef JSON_NO_AUTOMATIC_UDLS
-    #include <nlohmann/json_literals.hpp>
-#endif
-
 #endif  // INCLUDE_NLOHMANN_JSON_HPP_
@@ -1,83 +0,0 @@
-//     __ _____ _____ _____
-//  __|  |   __|     |   | |  JSON for Modern C++
-// |  |  |__   |  |  | | | |  version 3.12.0
-// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
-//
-// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
-// SPDX-License-Identifier: MIT
-
-#ifndef INCLUDE_NLOHMANN_JSON_LITERALS_HPP_
-#define INCLUDE_NLOHMANN_JSON_LITERALS_HPP_
-
-#include <cstddef> // size_t
-#include <string> // string
-
-#include <nlohmann/json.hpp>
-
-// This header is included at the end of <nlohmann/json.hpp> unless
-// JSON_NO_AUTOMATIC_UDLS is defined, and can be included on its own after that.
-// Either way, the library's internal macros are no longer defined here (and the
-// amalgamation inlines macro_scope.hpp only once), so only standard and public
-// macros may be used below.
-
-NLOHMANN_JSON_NAMESPACE_BEGIN
-inline namespace literals
-{
-inline namespace json_literals
-{
-
-/// @brief user-defined string literal for JSON values
-/// @sa https://json.nlohmann.me/api/operator_literal_json/
-#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
-    inline nlohmann::json operator""_json(const char* s, std::size_t n)
-#else
-    // GCC 4.8 requires a space between "" and suffix
-    inline nlohmann::json operator"" _json(const char* s, std::size_t n)
-#endif
-{
-    return nlohmann::json::parse(s, s + n);
-}
-
-#if defined(__cpp_char8_t)
-inline nlohmann::json operator""_json(const char8_t* s, std::size_t n)
-{
-    return nlohmann::json::parse(reinterpret_cast<const char*>(s),
-                                 reinterpret_cast<const char*>(s) + n);
-}
-#endif
-
-/// @brief user-defined string literal for JSON pointer
-/// @sa https://json.nlohmann.me/api/operator_literal_json_pointer/
-#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
-    inline nlohmann::json::json_pointer operator""_json_pointer(const char* s, std::size_t n)
-#else
-    // GCC 4.8 requires a space between "" and suffix
-    inline nlohmann::json::json_pointer operator"" _json_pointer(const char* s, std::size_t n)
-#endif
-{
-    return nlohmann::json::json_pointer(std::string(s, n));
-}
-
-#if defined(__cpp_char8_t)
-inline nlohmann::json::json_pointer operator""_json_pointer(const char8_t* s, std::size_t n)
-{
-    return nlohmann::json::json_pointer(std::string(reinterpret_cast<const char*>(s), n));
-}
-#endif
-
-}  // namespace json_literals
-}  // namespace literals
-NLOHMANN_JSON_NAMESPACE_END
-
-#if !defined(JSON_USE_GLOBAL_UDLS) || JSON_USE_GLOBAL_UDLS
-    #if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
-        using nlohmann::literals::json_literals::operator""_json; // NOLINT(misc-unused-using-decls,google-global-names-in-headers)
-        using nlohmann::literals::json_literals::operator""_json_pointer; //NOLINT(misc-unused-using-decls,google-global-names-in-headers)
-    #else
-        // GCC 4.8 requires a space between "" and suffix
-        using nlohmann::literals::json_literals::operator"" _json; // NOLINT(misc-unused-using-decls,google-global-names-in-headers)
-        using nlohmann::literals::json_literals::operator"" _json_pointer; //NOLINT(misc-unused-using-decls,google-global-names-in-headers)
-    #endif
-#endif
-
-#endif  // INCLUDE_NLOHMANN_JSON_LITERALS_HPP_
@@ -15,7 +15,6 @@ nlohmann_json_multiple_headers = declare_dependency(
 if not meson.is_subproject()
 install_headers('single_include/nlohmann/json.hpp', subdir: 'nlohmann')
 install_headers('single_include/nlohmann/json_fwd.hpp', subdir: 'nlohmann')
-install_headers('single_include/nlohmann/json_literals.hpp', subdir: 'nlohmann')

 pkgc = import('pkgconfig')
 pkgc.generate(name: 'nlohmann_json',
@@ -3327,6 +3327,10 @@ void templated_json_throw(ExceptionType exception)
    #define JSON_DISABLE_ENUM_SERIALIZATION 0
 #endif

+#ifndef JSON_USE_GLOBAL_UDLS
+    #define JSON_USE_GLOBAL_UDLS 1
+#endif
+
 #if JSON_HAS_THREE_WAY_COMPARISON
    #include <compare> // partial_ordering
 #endif
@@ -32500,6 +32504,55 @@ std::string format_as(const NLOHMANN_BASIC_JSON_TPL& j)
    return j.dump();
 }

+inline namespace literals
+{
+inline namespace json_literals
+{
+
+/// @brief user-defined string literal for JSON values
+/// @sa https://json.nlohmann.me/api/basic_json/operator_literal_json/
+JSON_HEDLEY_NON_NULL(1)
+#if !defined(JSON_HEDLEY_GCC_VERSION) || JSON_HEDLEY_GCC_VERSION_CHECK(4,9,0)
+    inline nlohmann::json operator""_json(const char* s, std::size_t n)
+#else
+    // GCC 4.8 requires a space between "" and suffix
+    inline nlohmann::json operator"" _json(const char* s, std::size_t n)
+#endif
+{
+    return nlohmann::json::parse(s, s + n);
+}
+
+#if defined(__cpp_char8_t)
+JSON_HEDLEY_NON_NULL(1)
+inline nlohmann::json operator""_json(const char8_t* s, std::size_t n)
+{
+    return nlohmann::json::parse(reinterpret_cast<const char*>(s),
+                                 reinterpret_cast<const char*>(s) + n);
+}
+#endif
+
+/// @brief user-defined string literal for JSON pointer
+/// @sa https://json.nlohmann.me/api/basic_json/operator_literal_json_pointer/
+JSON_HEDLEY_NON_NULL(1)
+#if !defined(JSON_HEDLEY_GCC_VERSION) || JSON_HEDLEY_GCC_VERSION_CHECK(4,9,0)
+    inline nlohmann::json::json_pointer operator""_json_pointer(const char* s, std::size_t n)
+#else
+    // GCC 4.8 requires a space between "" and suffix
+    inline nlohmann::json::json_pointer operator"" _json_pointer(const char* s, std::size_t n)
+#endif
+{
+    return nlohmann::json::json_pointer(std::string(s, n));
+}
+
+#if defined(__cpp_char8_t)
+inline nlohmann::json::json_pointer operator""_json_pointer(const char8_t* s, std::size_t n)
+{
+    return nlohmann::json::json_pointer(std::string(reinterpret_cast<const char*>(s), n));
+}
+#endif
+
+}  // namespace json_literals
+}  // namespace literals
 NLOHMANN_JSON_NAMESPACE_END

 ///////////////////////
@@ -32634,6 +32687,17 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c

 }  // namespace std

+#if JSON_USE_GLOBAL_UDLS
+    #if !defined(JSON_HEDLEY_GCC_VERSION) || JSON_HEDLEY_GCC_VERSION_CHECK(4,9,0)
+        using nlohmann::literals::json_literals::operator""_json; // NOLINT(misc-unused-using-decls,google-global-names-in-headers)
+        using nlohmann::literals::json_literals::operator""_json_pointer; //NOLINT(misc-unused-using-decls,google-global-names-in-headers)
+    #else
+        // GCC 4.8 requires a space between "" and suffix
+        using nlohmann::literals::json_literals::operator"" _json; // NOLINT(misc-unused-using-decls,google-global-names-in-headers)
+        using nlohmann::literals::json_literals::operator"" _json_pointer; //NOLINT(misc-unused-using-decls,google-global-names-in-headers)
+    #endif
+#endif
+
 // #include <nlohmann/detail/macro_unscope.hpp>
 //     __ _____ _____ _____
 //  __|  |   __|     |   | |  JSON for Modern C++
@@ -32662,6 +32726,7 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
 #undef JSON_INLINE_VARIABLE
 #undef JSON_NO_UNIQUE_ADDRESS
 #undef JSON_DISABLE_ENUM_SERIALIZATION
+#undef JSON_USE_GLOBAL_UDLS

 #ifndef JSON_TEST_KEEP_MACROS
    #undef JSON_CATCH
@@ -32854,97 +32919,4 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
    #pragma GCC diagnostic pop
 #endif

-// The user-defined string literals are in a separate header, because their
-// bodies instantiate the parser in every translation unit that includes them.
-// Define JSON_NO_AUTOMATIC_UDLS to include <nlohmann/json_literals.hpp> only
-// where needed.
-#ifndef JSON_NO_AUTOMATIC_UDLS
-// #include <nlohmann/json_literals.hpp>
-//     __ _____ _____ _____
-//  __|  |   __|     |   | |  JSON for Modern C++
-// |  |  |__   |  |  | | | |  version 3.12.0
-// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
-//
-// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
-// SPDX-License-Identifier: MIT
-
-#ifndef INCLUDE_NLOHMANN_JSON_LITERALS_HPP_
-#define INCLUDE_NLOHMANN_JSON_LITERALS_HPP_
-
-#include <cstddef> // size_t
-#include <string> // string
-
-// #include <nlohmann/json.hpp>
-
-
-// This header is included at the end of <nlohmann/json.hpp> unless
-// JSON_NO_AUTOMATIC_UDLS is defined, and can be included on its own after that.
-// Either way, the library's internal macros are no longer defined here (and the
-// amalgamation inlines macro_scope.hpp only once), so only standard and public
-// macros may be used below.
-
-NLOHMANN_JSON_NAMESPACE_BEGIN
-inline namespace literals
-{
-inline namespace json_literals
-{
-
-/// @brief user-defined string literal for JSON values
-/// @sa https://json.nlohmann.me/api/operator_literal_json/
-#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
-    inline nlohmann::json operator""_json(const char* s, std::size_t n)
-#else
-    // GCC 4.8 requires a space between "" and suffix
-    inline nlohmann::json operator"" _json(const char* s, std::size_t n)
-#endif
-{
-    return nlohmann::json::parse(s, s + n);
-}
-
-#if defined(__cpp_char8_t)
-inline nlohmann::json operator""_json(const char8_t* s, std::size_t n)
-{
-    return nlohmann::json::parse(reinterpret_cast<const char*>(s),
-                                 reinterpret_cast<const char*>(s) + n);
-}
-#endif
-
-/// @brief user-defined string literal for JSON pointer
-/// @sa https://json.nlohmann.me/api/operator_literal_json_pointer/
-#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
-    inline nlohmann::json::json_pointer operator""_json_pointer(const char* s, std::size_t n)
-#else
-    // GCC 4.8 requires a space between "" and suffix
-    inline nlohmann::json::json_pointer operator"" _json_pointer(const char* s, std::size_t n)
-#endif
-{
-    return nlohmann::json::json_pointer(std::string(s, n));
-}
-
-#if defined(__cpp_char8_t)
-inline nlohmann::json::json_pointer operator""_json_pointer(const char8_t* s, std::size_t n)
-{
-    return nlohmann::json::json_pointer(std::string(reinterpret_cast<const char*>(s), n));
-}
-#endif
-
-}  // namespace json_literals
-}  // namespace literals
-NLOHMANN_JSON_NAMESPACE_END
-
-#if !defined(JSON_USE_GLOBAL_UDLS) || JSON_USE_GLOBAL_UDLS
-    #if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
-        using nlohmann::literals::json_literals::operator""_json; // NOLINT(misc-unused-using-decls,google-global-names-in-headers)
-        using nlohmann::literals::json_literals::operator""_json_pointer; //NOLINT(misc-unused-using-decls,google-global-names-in-headers)
-    #else
-        // GCC 4.8 requires a space between "" and suffix
-        using nlohmann::literals::json_literals::operator"" _json; // NOLINT(misc-unused-using-decls,google-global-names-in-headers)
-        using nlohmann::literals::json_literals::operator"" _json_pointer; //NOLINT(misc-unused-using-decls,google-global-names-in-headers)
-    #endif
-#endif
-
-#endif  // INCLUDE_NLOHMANN_JSON_LITERALS_HPP_
-
-#endif
-
 #endif  // INCLUDE_NLOHMANN_JSON_HPP_
@@ -1,83 +0,0 @@
-//     __ _____ _____ _____
-//  __|  |   __|     |   | |  JSON for Modern C++
-// |  |  |__   |  |  | | | |  version 3.12.0
-// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
-//
-// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
-// SPDX-License-Identifier: MIT
-
-#ifndef INCLUDE_NLOHMANN_JSON_LITERALS_HPP_
-#define INCLUDE_NLOHMANN_JSON_LITERALS_HPP_
-
-#include <cstddef> // size_t
-#include <string> // string
-
-#include <nlohmann/json.hpp>
-
-// This header is included at the end of <nlohmann/json.hpp> unless
-// JSON_NO_AUTOMATIC_UDLS is defined, and can be included on its own after that.
-// Either way, the library's internal macros are no longer defined here (and the
-// amalgamation inlines macro_scope.hpp only once), so only standard and public
-// macros may be used below.
-
-NLOHMANN_JSON_NAMESPACE_BEGIN
-inline namespace literals
-{
-inline namespace json_literals
-{
-
-/// @brief user-defined string literal for JSON values
-/// @sa https://json.nlohmann.me/api/operator_literal_json/
-#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
-    inline nlohmann::json operator""_json(const char* s, std::size_t n)
-#else
-    // GCC 4.8 requires a space between "" and suffix
-    inline nlohmann::json operator"" _json(const char* s, std::size_t n)
-#endif
-{
-    return nlohmann::json::parse(s, s + n);
-}
-
-#if defined(__cpp_char8_t)
-inline nlohmann::json operator""_json(const char8_t* s, std::size_t n)
-{
-    return nlohmann::json::parse(reinterpret_cast<const char*>(s),
-                                 reinterpret_cast<const char*>(s) + n);
-}
-#endif
-
-/// @brief user-defined string literal for JSON pointer
-/// @sa https://json.nlohmann.me/api/operator_literal_json_pointer/
-#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
-    inline nlohmann::json::json_pointer operator""_json_pointer(const char* s, std::size_t n)
-#else
-    // GCC 4.8 requires a space between "" and suffix
-    inline nlohmann::json::json_pointer operator"" _json_pointer(const char* s, std::size_t n)
-#endif
-{
-    return nlohmann::json::json_pointer(std::string(s, n));
-}
-
-#if defined(__cpp_char8_t)
-inline nlohmann::json::json_pointer operator""_json_pointer(const char8_t* s, std::size_t n)
-{
-    return nlohmann::json::json_pointer(std::string(reinterpret_cast<const char*>(s), n));
-}
-#endif
-
-}  // namespace json_literals
-}  // namespace literals
-NLOHMANN_JSON_NAMESPACE_END
-
-#if !defined(JSON_USE_GLOBAL_UDLS) || JSON_USE_GLOBAL_UDLS
-    #if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
-        using nlohmann::literals::json_literals::operator""_json; // NOLINT(misc-unused-using-decls,google-global-names-in-headers)
-        using nlohmann::literals::json_literals::operator""_json_pointer; //NOLINT(misc-unused-using-decls,google-global-names-in-headers)
-    #else
-        // GCC 4.8 requires a space between "" and suffix
-        using nlohmann::literals::json_literals::operator"" _json; // NOLINT(misc-unused-using-decls,google-global-names-in-headers)
-        using nlohmann::literals::json_literals::operator"" _json_pointer; //NOLINT(misc-unused-using-decls,google-global-names-in-headers)
-    #endif
-#endif
-
-#endif  // INCLUDE_NLOHMANN_JSON_LITERALS_HPP_
@@ -18,7 +18,6 @@ module;
 // See: https://github.com/nlohmann/json/issues/5103

 #include <nlohmann/json.hpp>
-#include <nlohmann/json_literals.hpp>

 export module nlohmann.json;

@@ -1,97 +0,0 @@
-//     __ _____ _____ _____
-//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
-// |  |  |__   |  |  | | | |  version 3.12.0
-// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
-//
-// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
-// SPDX-License-Identifier: MIT
-
-// This translation unit checks JSON_NO_AUTOMATIC_UDLS, which keeps
-// <nlohmann/json.hpp> from including <nlohmann/json_literals.hpp> and thereby
-// leaves out the user-defined string literals operator""_json and
-// operator""_json_pointer (see #5294), and that including
-// <nlohmann/json_literals.hpp> afterwards brings them back.
-#define JSON_NO_AUTOMATIC_UDLS 1
-
-#include "doctest_compatibility.h"
-
-#include <cstddef>
-#include <utility>
-
-#include <nlohmann/json.hpp>
-using json = nlohmann::json;
-
-// An argument type whose associated namespace is the library namespace, so
-// argument-dependent lookup of a literal operator called by its function name
-// also searches the inline namespaces nlohmann::literals::json_literals.
-NLOHMANN_JSON_NAMESPACE_BEGIN
-struct no_automatic_udls_probe
-{
-    operator const char* () const // NOLINT(google-explicit-constructor,hicpp-explicit-conversions)
-    {
-        return "";
-    }
-};
-NLOHMANN_JSON_NAMESPACE_END
-
-namespace
-{
-// The calls below use a dependent argument, so a literal operator that is not
-// declared at all is a substitution failure rather than a hard error: lookup is
-// deferred to the point of instantiation, where it considers the declarations
-// visible from here (the global using-declarations of JSON_USE_GLOBAL_UDLS) plus
-// argument-dependent lookup (the literals in the library namespace).
-template<typename T>
-using json_udl_t = decltype(operator""_json(std::declval<T>(), std::size_t()));
-
-template<typename T>
-using json_pointer_udl_t = decltype(operator""_json_pointer(std::declval<T>(), std::size_t()));
-
-template<typename T>
-using has_json_udl = nlohmann::detail::is_detected<json_udl_t, T>;
-
-template<typename T>
-using has_json_pointer_udl = nlohmann::detail::is_detected<json_pointer_udl_t, T>;
-} // namespace
-
-TEST_CASE("JSON_NO_AUTOMATIC_UDLS")
-{
-    SECTION("literals are not declared")
-    {
-        // global namespace (JSON_USE_GLOBAL_UDLS defaults to 1)
-        CHECK_FALSE(has_json_udl<const char*>::value);
-        CHECK_FALSE(has_json_pointer_udl<const char*>::value);
-
-        // nlohmann::literals::json_literals
-        CHECK_FALSE(has_json_udl<nlohmann::no_automatic_udls_probe>::value);
-        CHECK_FALSE(has_json_pointer_udl<nlohmann::no_automatic_udls_probe>::value);
-    }
-
-    SECTION("the rest of the library keeps working")
-    {
-        const json j = json::parse(R"({"foo": {"bar": 42}})");
-        CHECK(j.dump() == R"({"foo":{"bar":42}})");
-
-        const json::json_pointer ptr("/foo/bar");
-        CHECK(j.at(ptr) == 42);
-        CHECK(j.contains(ptr));
-    }
-}
-
-// the literals can still be added where they are needed
-#include <nlohmann/json_literals.hpp>
-
-TEST_CASE("JSON_NO_AUTOMATIC_UDLS with <nlohmann/json_literals.hpp>")
-{
-    SECTION("global namespace")
-    {
-        CHECK("[1,2]"_json == json({1, 2}));
-        CHECK("/a/0"_json_pointer == json::json_pointer("/a/0"));
-    }
-
-    SECTION("nlohmann::literals::json_literals")
-    {
-        using namespace nlohmann::literals::json_literals; // NOLINT(google-build-using-namespace)
-        CHECK(R"({"a":[42]})"_json.at("/a/0"_json_pointer) == 42);
-    }
-}
Author	SHA1	Message	Date
Niels Lohmann	53fc09b3ab	Merge branch 'develop' into claude/3453-breaking-change-flags-c937b4 Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-28 22:22:39 +02:00
Niels Lohmann	c6878de6a7	Add JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON to the 4.0 example Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-28 18:47:31 +02:00
Niels Lohmann	8502d73729	Merge branch 'develop' into claude/3453-breaking-change-flags-c937b4 Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-27 20:58:00 +02:00
Niels Lohmann	3d18d2b7c5	Wrap overlong line in cbor_tag_handler_t documentation The line added in #5559 exceeds the 160-character limit enforced by the documentation style check. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-27 16:55:18 +02:00
Niels Lohmann	fb3d9d9b8f	List the deprecated functions removed in 4.0 in the roadmap The roadmap lists what will be removed; the migration guide keeps the examples for how to replace each item. Also mention the deprecated (ptr, len) overloads of the from_* functions in the migration guide. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-27 16:51:39 +02:00
Niels Lohmann	a164f926c5	Document the macros that preview version 4.0 in the roadmap List the macros that guard breaking changes planned to become the default in version 4.0.0, and explain that 4.0.0 will be the sum of these opt-in flags, which can be tried on the 3.x release train. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-09-27 16:39:52 +02:00