Bump lukka/get-cmake from 4.4.5 to 4.5.0

get-cmake 4.4.5 does not know CMake 4.5.0, so the ci_module_cpp20 jobs
that request '^4.5.0' failed in the setup step. Bump every pin so all
jobs use the same action version.

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

.github/workflows/ubuntu.yml

@@ -25,7 +25,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Run CMake
         run: cmake -S . -B build -DJSON_CI=On
       - name: Build
@@ -38,7 +38,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Check that Meson and pkg-config offer the CMake options
         run: make check_build_options
       - name: Install Meson
@@ -92,7 +92,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Run CMake
         run: cmake -S . -B build -DJSON_CI=On
       - name: Build
@@ -123,7 +123,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Run CMake
         run: cmake -S . -B build -DJSON_CI=On
       - name: Build
@@ -142,7 +142,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Run CMake
         run: cmake -S . -B build -DJSON_CI=On
       - name: Build
@@ -168,7 +168,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Run CMake
         run: cmake -S . -B build -DJSON_CI=On
       - name: Build
@@ -244,7 +244,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Run CMake
         run: CXX=g++-${{ matrix.compiler }} cmake -S . -B build -DJSON_CI=On
       - name: Build
@@ -262,7 +262,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Run CMake
         run: cmake -S . -B build -DJSON_CI=On
       - name: Build
@@ -279,7 +279,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Disable filesystem support (std::filesystem is unusable) for clang 7 / 8 / 9 / 10
         run: echo "JSON_FORCED_GLOBAL_COMPILE_OPTIONS=-DJSON_HAS_FILESYSTEM=0;-DJSON_HAS_EXPERIMENTAL_FILESYSTEM=0" >> "$GITHUB_ENV"
         if: ${{ matrix.compiler == '7' || matrix.compiler == '8' || matrix.compiler == '9' || matrix.compiler == '10' }}
@@ -299,7 +299,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Run CMake
         run: cmake -S . -B build -DJSON_CI=On
       - name: Build
@@ -319,7 +319,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Run CMake
         run: cmake -S . -B build -DJSON_CI=On
       - name: Build with libc++
@@ -346,7 +346,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Run CMake
         run: cmake -S . -B build -DJSON_CI=On
       - name: Build
@@ -362,13 +362,11 @@ jobs:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           persist-credentials: false
-      # The module test uses `import std;`, which needs CMake's experimental
+      # The module test uses `import std;`, which needs CMake 4.5 or newer.
-      # import-std support. Its opt-in token is CMake-version-specific, so pin
+      - name: Get CMake 4.5+ and ninja
-      # CMake to the version whose token is set in tests/module_cpp20/CMakeLists.txt.
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
-      - name: Get pinned CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
         with:
-          cmakeVersion: 4.3.4
+          cmakeVersion: '^4.5.0'
       # Clang: the std library module is provided by libc++ (the image's libstdc++
       # ships none), and the image's libc++ module manifest has a broken relative
       # path — repoint it at the real module sources.
@@ -392,7 +390,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Run CMake
         run: cmake -S . -B build -DJSON_CI=On
       - name: Build
@@ -409,7 +407,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Run CMake
         run: cmake -S . -B build -DJSON_CI=On
       - name: Build
@@ -423,7 +421,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Run CMake
         run: cmake -S . -B build -DJSON_CI=On
       - name: Build
@@ -443,7 +441,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Run CMake
         run: cmake -S . -B build -DCMAKE_TOOLCHAIN_FILE=$EMSDK/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake -GNinja
       - name: Build
@@ -484,7 +482,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Check that the job runs natively on arm64
         run: uname -m && test "$(uname -m)" = aarch64
       - name: Run CMake

.github/workflows/windows.yml

@@ -90,7 +90,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
       - name: Set extra CXX_FLAGS for latest std_version
         # /wd5285 silences C5285 emitted by the bundled third-party doctest.h, which
         # specializes std::tuple (newly diagnosed by the VS2026 v145 toolset)
@@ -212,13 +212,11 @@ jobs:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           persist-credentials: false
-      # The module test uses `import std;`, which needs CMake's experimental
+      # The module test uses `import std;`, which needs CMake 4.5 or newer.
-      # import-std support. Its opt-in token is CMake-version-specific, so pin
+      - name: Get CMake 4.5+ and ninja
-      # CMake to the version whose token is set in tests/module_cpp20/CMakeLists.txt.
+        uses: lukka/get-cmake@16e8153a8b4918849d92aad131befe67a3705daa # v4.5.0
-      - name: Get pinned CMake and ninja
-        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
         with:
-          cmakeVersion: 4.3.4
+          cmakeVersion: '^4.5.0'
       # CMAKE_CXX_FLAGS replaces CMake's MSVC defaults (which include /EHsc), and
       # ci_module_cpp20 forwards it to the module build, so list /EHsc explicitly
       - name: Run CMake (Debug)

README.md

@@ -165,7 +165,8 @@ std::ifstream f("example.json");
 json data = json::parse(f);
 ```
 
-If using modules (enabled with `NLOHMANN_JSON_BUILD_MODULES`), this example becomes:
+If using modules (enabled with `NLOHMANN_JSON_BUILD_MODULES`; `import std;` needs CMake 4.5 or newer, see the
+[modules documentation](https://json.nlohmann.me/features/modules/)), this example becomes:
 ```cpp
 import std;
 import nlohmann.json;

docs/mkdocs/docs/api/basic_json/dump.md

@@ -58,9 +58,7 @@ is not UTF-8 encoded and `error_handler` is set to `strict`
 
 ## Complexity
 
-Linear in the size of the result. With an `indent`, every line starts with up to `indent` characters per nesting level,
+Linear.
-so the result can be larger than the value by a factor of its nesting depth (see
-[Parsing untrusted input](../../features/parsing/untrusted_input.md#nesting-depth)).
 
 ## Notes
 

docs/mkdocs/docs/api/basic_json/flatten.md

@@ -18,8 +18,7 @@ Strong exception safety: if an exception occurs, the original value stays intact
 
 ## Complexity
 
-Linear in the size of the result. Every key repeats the path of its value, so the keys can be larger than the value by a
+Linear in the size of the JSON value.
-factor of its nesting depth (see [Parsing untrusted input](../../features/parsing/untrusted_input.md#nesting-depth)).
 
 ## Notes
 

docs/mkdocs/docs/api/ordered_map.md

@@ -89,21 +89,19 @@ This differs from `#!cpp std::map`, where the same operations are O(log n).
 !!! warning "Quadratic cost of building large objects"
 
     Because every insertion scans all elements inserted so far, building an object of `n` distinct keys costs
-    **O(n²)** in total. This applies to filling an [`ordered_json`](ordered_json.md) object key by key (with
+    **O(n²)** in total. This applies to filling an [`ordered_json`](ordered_json.md) object key by key as well as to
-    `operator[]`, `emplace`, or `insert`) and, for now, to reading one with a binary reader such as
+    parsing one, since the parser inserts each key as it is read.
-    [`from_cbor`](basic_json/from_cbor.md) ([#6104](https://github.com/nlohmann/json/issues/6104)). Parsing JSON text
-    is not affected: the parser finds the keys of an object with many members in a hash table and takes linear time.
 
     The cost is negligible for the object sizes typically found in configuration files or API payloads, but it grows
-    steeply for machine-generated objects with many thousands of keys. Measured with Apple clang 21, `-O2 -DNDEBUG`,
+    steeply for machine-generated objects with many thousands of keys. Measured with `-O2 -DNDEBUG` for parsing a flat
-    arm64, for a flat object of `n` keys (best of seven runs):
+    object of `n` keys, relative to `#!cpp nlohmann::json` (which uses `#!cpp std::map`):
 
-    | `n`    | `json::parse` | `ordered_json::parse` | `ordered_json`, key by key | `ordered_json::from_cbor` |
+    | `n`    | `json` | `ordered_json` | factor |
-    |--------|---------------|-----------------------|----------------------------|---------------------------|
+    |--------|--------|----------------|--------|
-    | 2000   | 0.3 ms        | 0.1 ms                | 4.5 ms                     | 4.4 ms                    |
+    | 2000   | 0.7 ms | 3.6 ms         | 5×     |
-    | 4000   | 0.5 ms        | 0.2 ms                | 17.1 ms                    | 16.8 ms                   |
+    | 4000   | 0.8 ms | 14.0 ms        | 19×    |
-    | 8000   | 0.9 ms        | 0.3 ms                | 67.0 ms                    | 66.8 ms                   |
+    | 8000   | 1.6 ms | 67.8 ms        | 43×    |
-    | 16 000 | 2.0 ms        | 0.7 ms                | 282.4 ms                   | 282.4 ms                  |
+    | 16 000 | 3.3 ms | 181.6 ms       | 54×    |
 
     If key order matters for objects of that size, consider a container with a lookup index, such as
     [`nlohmann::fifo_map`](https://github.com/nlohmann/fifo_map)

docs/mkdocs/docs/features/modules.md

@@ -9,7 +9,19 @@ Importing the module instead of including the header reduces the compile time of
 ## Requirements
 The `nlohmann.json` module requires that the build system is configured to build and resolve modules when imported. Obviously, as modules were introduced in C++20, this feature can only be used in C++20 and subsequent versions.
 
-To enable building the `nlohmann.json` module (which is not done by default), the macro `NLOHMANN_JSON_BUILD_MODULES` must be passed to the build system.
+To enable building the `nlohmann.json` module (which is not done by default), set the CMake option
+[`NLOHMANN_JSON_BUILD_MODULES`](../integration/cmake.md#nlohmann_json_build_modules) and link the
+`nlohmann_json_modules` target.
+
+With CMake, building the module needs:
+
+- CMake 3.28 or newer, and
+- a generator that scans for modules: Ninja (1.11 or newer), Ninja Multi-Config, or Visual Studio 2022 or newer.
+
+The example below also uses `import std;`. CMake supports it without experimental opt-in since version 4.5, and then
+only with the Ninja generators and these toolchains: Clang 18.1.2 or newer (with libc++ or libstdc++), MSVC toolset 14.36
+(Visual Studio 17.6) or newer, and GCC 15 or newer (GCC 16 on macOS). With older CMake versions, `import std;` needs
+CMake's version-specific experimental opt-in.
 
 ## Example
 When using modules rather than headers, the previous example for creating a `json` object through a JSON file, would instead be:
@@ -67,7 +79,7 @@ and should not be used directly:
 
 ## Known issues
 
-C++20 modules support is exercised in CI against current GCC and Clang on Ubuntu, and the default MSVC toolset on Windows Server 2022 — there is no documented minimum compiler version, unlike feature-test-macro-gated features such as [`JSON_HAS_RANGES`](../api/macros/json_has_ranges.md).
+C++20 modules support is exercised in CI with CMake 4.5 and `import std;` against current GCC and Clang on Ubuntu, and the default MSVC toolset on Windows Server 2022 — there is no documented minimum compiler version, unlike feature-test-macro-gated features such as [`JSON_HAS_RANGES`](../api/macros/json_has_ranges.md).
 
 !!! info "Known compiler issues"
 

docs/mkdocs/docs/features/parsing/untrusted_input.md

@@ -81,20 +81,6 @@ result. See the [documentation of the macro](../../api/macros/json_recursion_dep
 the speed, and the rules for choosing a value. Destroying a value (its destructor) recurses over the same number of
 levels and then continues without the call stack, and needs 32 KiB or less at every limit.
 
-!!! warning "Indented output and flattened keys grow with the depth"
-
-    Some results are larger than the value by a factor of its nesting depth.
-    [`dump`](../../api/basic_json/dump.md) with an `indent` of `n` (and likewise `operator<<` with `std::setw(n)` and
-    [`basic_json_view::dump`](../../api/basic_json_view/dump.md)) writes up to `n` characters per nesting level in
-    front of every line, and [`flatten`](../../api/basic_json/flatten.md) repeats the path of every value in its key.
-    For the 80,001-byte array `[1,[1,...[1,1]...]]` with 20,000 levels, `dump(1)` returns 600 MB, `dump(4)` 2.4 GB,
-    and the keys of `flatten()` hold 400 MB. A compact `dump()` without indentation stays the size of the value. If you
-    pretty-print, log, or flatten untrusted input, limit its nesting depth while parsing, for example with a
-    [parser callback](parser_callbacks.md#recipe-max-nesting-depth-via-a-callback): with a limit of `d`, every line has
-    at most `n * d` indentation characters, and every flattened key has at most `d` reference tokens.
-    [`JSON_RECURSION_DEPTH_LIMIT`](../../api/macros/json_recursion_depth_limit.md) does not help here: it changes only
-    how much of the call stack a walk uses, never its result, and it does not limit the depth that `parse()` accepts.
-
 ## Input size
 
 The library does not limit the overall size of a JSON text; a value nested or wide enough will use memory
@@ -154,20 +140,6 @@ values for a repeated key ends up in the parsed object. If your application must
 silently resolving them one way or another, see the
 [parser callback recipe for rejecting duplicate keys](parser_callbacks.md#recipe-rejecting-duplicate-object-keys).
 
-## Objects with many keys in `ordered_json`
-
-[`ordered_json`](../../api/ordered_json.md) keeps the members of an object in a vector in insertion order
-([`ordered_map`](../../api/ordered_map.md)) and finds a key by searching all members. Parsing JSON text into an
-`ordered_json` avoids that search for objects with many keys and takes linear time. The binary readers
-([`from_cbor`](../../api/basic_json/from_cbor.md), [`from_msgpack`](../../api/basic_json/from_msgpack.md),
-[`from_ubjson`](../../api/basic_json/from_ubjson.md), [`from_bjdata`](../../api/basic_json/from_bjdata.md),
-[`from_bson`](../../api/basic_json/from_bson.md), and [`from_bon8`](../../api/basic_json/from_bon8.md)) do not yet:
-reading an object of `n` keys into an `ordered_json` costs time proportional to `n²`. A flat object of 40,000 keys
-(about 300 KB of CBOR) takes about 1.3 s, against a few milliseconds as JSON text or into a `json`
-([#6104](https://github.com/nlohmann/json/issues/6104)). `json` is not affected. If you read untrusted binary input
-into `ordered_json`, bound the input size more tightly, read it into a `json`, or reject objects with many keys in a
-[SAX handler](sax_interface.md).
-
 ## Numbers
 
 A number whose value cannot be represented — for instance `1E1000`, which overflows `double` — is rejected while
@@ -199,11 +171,9 @@ indices (or the pointer as a whole) before using them, or use [`at`](../../api/b
 
 - Wrap parsing in a `#!cpp try`/`#!cpp catch` block, or use `allow_exceptions=false`/`accept()` if your environment
   cannot use exceptions; never let `JSON_NOEXCEPTION`'s `abort()` be the first time you think about error handling.
-- If the input's nesting depth matters to you (for example because you pretty-print, log, or flatten it), enforce your
+- If the input's nesting depth matters to you, enforce your own limit with a
-  own limit with a [parser callback](parser_callbacks.md#recipe-max-nesting-depth-via-a-callback) or a
+  [parser callback](parser_callbacks.md#recipe-max-nesting-depth-via-a-callback) or a
   [SAX handler](sax_interface.md); the library bounds the call stack but not memory use.
-- If you read untrusted binary input into `ordered_json`, mind that objects with many keys are
-  [slow to read](#objects-with-many-keys-in-ordered_json).
 - Bound the size of the input itself before parsing, independent of the library's own bounded allocations for binary
   format lengths.
 - Decide up front how you want a string with invalid UTF-8 — from any source, not only parsing — to be serialized

docs/mkdocs/docs/integration/cmake.md

@@ -269,6 +269,9 @@ target_link_libraries(myproject PRIVATE nlohmann_json_modules)
 target_compile_definitions(myproject PRIVATE NLOHMANN_JSON_BUILD_MODULES)
 ```
 
+If `main.cpp` also uses `import std;`, the project needs CMake 4.5 or newer and a Ninja generator; see
+[Modules](../features/modules.md#requirements) for the supported toolchains.
+
 ## See also
 
 - [Macros](../api/macros/index.md) - reference of all macros

tests/module_cpp20/CMakeLists.txt

@@ -1,11 +1,6 @@
-cmake_minimum_required(VERSION 3.30)
+# `import std;` (used by main.cpp) is supported without experimental opt-in
-
+# since CMake 4.5: it is available to every target that scans for C++ modules.
-# `import std;` (used by main.cpp) needs CMake's experimental C++ import-std
+cmake_minimum_required(VERSION 4.5)
-# support. The accepted token is CMake-version-specific; this value matches the
-# CMake version pinned in the ci_module_cpp20 CI jobs (4.3.x). If that pin is
-# bumped, this token must be updated to match (configuration fails loudly
-# otherwise).
-set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD "451f2fe2-a8a2-47c3-bc32-94786d8fc91b")
 
 project(json_test CXX)
 
@@ -13,7 +8,6 @@ project(json_test CXX)
 set(CMAKE_CXX_STANDARD 23)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
-set(CMAKE_CXX_MODULE_STD ON)
 
 set(NLOHMANN_JSON_BUILD_MODULES ON CACHE BOOL "Enable nlohmann.json module support")
 

tests/module_cpp20/main.cpp

@@ -17,8 +17,8 @@ using namespace nlohmann::literals;
 // Standard-library facilities are pulled in via `import std;` rather than
 // textual `#include`s: mixing `import` with textual standard headers does not
 // compile under GCC's C++20 modules implementation, whereas `import std;` works
-// across GCC, Clang, and MSVC. This requires C++23 and CMake's (experimental)
+// across GCC, Clang, and MSVC. This requires C++23 and CMake 4.5 or newer;
-// import-std support; see CMakeLists.txt.
+// see CMakeLists.txt.
 int main()
 {
     // basic_json / json: parsing and value access