Hide a discarded container's content from the parser callback

When a parser callback rejects an object's or array's start event,
json_sax_dom_callback_parser kept calling it for everything inside
that container anyway: nested keys, values, and the start/end events
of containers below it. This contradicts parser_callback_t's own
documentation, which promises that discarding a container at its
start event also hides its content from the callback.

The same code path also kept a full copy of every key inside such a
discarded container in key_stack until the whole parse finished,
because the early return for values that are not stored skipped the
matching pop. Filtering out a large subtree is the main reason to use
a callback, so this made peak memory during the parse scale with the
size of the very subtree the callback was trying to skip.

Fix start_object(), start_array(), and key() so that a container
whose own start event was discarded, or that is nested inside one, is
never handed to the callback, and no longer pushes onto the key
stacks. A container whose start event was accepted but whose key was
rejected still gets its content reported, as documented ("the
callback is still called for the associated value, but its return
value has no further effect"); only its own bookkeeping is skipped
since it will not be stored.

Fixes #5643.

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

.cirrus.yml

@@ -0,0 +1,17 @@
+arm_container:
+  image: gcc:latest
+
+check_task:
+  check_script:
+  # the gcc image ships an outdated CMake, so fetch a recent prebuilt binary
+  # instead of compiling CMake from source
+  - wget -q https://github.com/Kitware/CMake/releases/download/v4.3.4/cmake-4.3.4-linux-aarch64.tar.gz
+  - tar xfz cmake-4.3.4-linux-aarch64.tar.gz
+  - export PATH="$(pwd)/cmake-4.3.4-linux-aarch64/bin:$PATH"
+  - cmake --version
+  - mkdir build
+  - cd build
+  - cmake .. -DJSON_FastTests=ON
+  - make -j4
+  - cd tests
+  - ctest -j4

.github/dependabot.yml

@@ -24,10 +24,6 @@ updates:
       interval: daily
     cooldown:
       default-days: 7
-    ignore:
-      # astyle is deliberately pinned (see tools/astyle/requirements.txt): newer versions
-      # reformat the code, and the pinned version defines the formatting CI enforces
-      - dependency-name: astyle
 
   - package-ecosystem: pip
     directory: /tools/generate_natvis

.github/external_ci/appveyor.yml

@@ -30,6 +30,14 @@ environment:
       CMAKE_OPTIONS: ""
       GENERATOR: Visual Studio 14 2015
 
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      configuration: Release
+      platform: x86
+      name: with_win_header
+      CXX_FLAGS: "/W4 /WX"
+      CMAKE_OPTIONS: ""
+      GENERATOR: Visual Studio 14 2015
+
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
       configuration: Release
       platform: x86
@@ -66,6 +74,9 @@ install:
   - if "%platform%"=="x86"    set GENERATOR_PLATFORM=Win32
 
 before_build:
+  # for with_win_header build, inject the inclusion of Windows.h to the single-header library
+  - ps: if ($env:name -Eq "with_win_header") { $header_path = "single_include\nlohmann\json.hpp" }
+  - ps: if ($env:name -Eq "with_win_header") { "#include <Windows.h>`n" + (Get-Content $header_path | Out-String) | Set-Content $header_path }
   - cmake . -G "%GENERATOR%" -A "%GENERATOR_PLATFORM%" -DCMAKE_CXX_FLAGS="%CXX_FLAGS%" -DCMAKE_IGNORE_PATH="C:/Program Files/Git/usr/bin" -DJSON_BuildTests=On "%CMAKE_OPTIONS%"
 
 build_script:

.github/workflows/ubuntu.yml

@@ -403,21 +403,3 @@ jobs:
         run: cmake -S . -B build -DJSON_CI=On
       - name: Build
         run: cmake --build build --target ${{ matrix.target }}
-
-  # Native Linux ARM64 runner with the latest GCC. The ubuntu-24.04-arm label is
-  # only available for public repositories.
-  ci_test_arm64:
-    runs-on: ubuntu-24.04-arm
-    container: gcc:latest
-    steps:
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        with:
-          persist-credentials: false
-      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@fffaaafeea488556c2c12dad60690008bc1caacb # v4.4.2
-      - name: Check that the job runs natively on arm64
-        run: uname -m && test "$(uname -m)" = aarch64
-      - name: Run CMake
-        run: cmake -S . -B build -DJSON_CI=On
-      - name: Build
-        run: cmake --build build --target ci_test_compiler_default

FILES.md

@@ -33,6 +33,17 @@ Further documentation:
 > [!IMPORTANT]
 > The folder `.github/workflows` is predetermined by GitHub.
 
+### `.cirrus.yml`
+
+Configuration file for the pipeline at [Cirrus CI](https://cirrus-ci.com/github/nlohmann/json).
+
+Further documentation:
+
+- [Writing tasks](https://cirrus-ci.org/guide/writing-tasks/)
+
+> [!IMPORTANT]
+> The filename `.cirrus.yml` and position (root of the repository) are predetermined by Cirrus CI.
+
 ### `.github/external_ci/appveyor.yml`
 
 Configuration for the pipelines at [AppVeyor](https://ci.appveyor.com/project/nlohmann/json).

README.md

@@ -7,6 +7,7 @@
 [![Coverage Status](https://coveralls.io/repos/github/nlohmann/json/badge.svg?branch=develop)](https://coveralls.io/github/nlohmann/json?branch=develop)
 [![Coverity Scan Build Status](https://scan.coverity.com/projects/5550/badge.svg)](https://scan.coverity.com/projects/nlohmann-json)
 [![Codacy Badge](https://app.codacy.com/project/badge/Grade/e0d1a9d5d6fd46fcb655c4cb930bb3e8)](https://app.codacy.com/gh/nlohmann/json/dashboard?utm_source=gh&utm_medium=referral&utm_content=&utm_campaign=Badge_grade)
+[![Cirrus CI](https://api.cirrus-ci.com/github/nlohmann/json.svg)](https://cirrus-ci.com/github/nlohmann/json)
 [![Fuzzing Status](https://oss-fuzz-build-logs.storage.googleapis.com/badges/json.svg)](https://bugs.chromium.org/p/oss-fuzz/issues/list?sort=-opened&can=1&q=proj:json)
 [![Try online](https://img.shields.io/badge/try-online-blue.svg)](https://wandbox.org/permlink/1mp10JbaANo6FUc7)
 [![Documentation](https://img.shields.io/badge/docs-mkdocs-blue.svg)](https://json.nlohmann.me)

cmake/ci.cmake

@@ -55,6 +55,12 @@ execute_process(COMMAND ${NINJA_TOOL} --version OUTPUT_VARIABLE NINJA_TOOL_VERSI
 string(REGEX MATCH "[0-9]+(\\.[0-9]+)+" NINJA_TOOL_VERSION "${NINJA_TOOL_VERSION}")
 message(STATUS "🔖 Ninja ${NINJA_TOOL_VERSION} (${NINJA_TOOL})")
 
+find_program(OCLINT_TOOL NAMES oclint-json-compilation-database)
+find_program(OCLINT_VERSION_TOOL NAMES oclint)
+execute_process(COMMAND ${OCLINT_VERSION_TOOL} --version OUTPUT_VARIABLE OCLINT_TOOL_VERSION ERROR_VARIABLE OCLINT_TOOL_VERSION)
+string(REGEX MATCH "[0-9]+(\\.[0-9]+)+" OCLINT_TOOL_VERSION "${OCLINT_TOOL_VERSION}")
+message(STATUS "🔖 OCLint ${OCLINT_TOOL_VERSION} (${OCLINT_TOOL})")
+
 find_program(VALGRIND_TOOL NAMES valgrind)
 execute_process(COMMAND ${VALGRIND_TOOL} --version OUTPUT_VARIABLE VALGRIND_TOOL_VERSION ERROR_VARIABLE VALGRIND_TOOL_VERSION)
 string(REGEX MATCH "[0-9]+(\\.[0-9]+)+" VALGRIND_TOOL_VERSION "${VALGRIND_TOOL_VERSION}")
@@ -122,16 +128,16 @@ foreach(CXX_STANDARD 11 14 17 20 23 26)
         COMMENT "Compile and test with Clang for C++${CXX_STANDARD}"
     )
 
-    # pass -stdlib=libc++ through CXXFLAGS: an explicit -DCMAKE_CXX_FLAGS would make CMake ignore CXXFLAGS
     add_custom_target(ci_test_clang_libcxx_cxx${CXX_STANDARD}
-        COMMAND CXX=${CLANG_TOOL} CXXFLAGS="${CLANG_CXXFLAGS};-stdlib=libc++" ${CMAKE_COMMAND}
+        COMMAND CXX=${CLANG_TOOL} CXXFLAGS="${CLANG_CXXFLAGS}" ${CMAKE_COMMAND}
             -DCMAKE_BUILD_TYPE=Debug -GNinja
             -DJSON_BuildTests=ON -DJSON_FastTests=ON
             -DJSON_TestStandards=${CXX_STANDARD}
+            -DCMAKE_CXX_FLAGS="-stdlib=libc++"
             -DCMAKE_EXE_LINKER_FLAGS="-lc++abi"
-            -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_clang_libcxx_cxx${CXX_STANDARD}
-        COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_clang_libcxx_cxx${CXX_STANDARD}
-        COMMAND cd ${PROJECT_BINARY_DIR}/build_clang_libcxx_cxx${CXX_STANDARD} && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure
+            -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_clang_cxx${CXX_STANDARD}
+        COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_clang_cxx${CXX_STANDARD}
+        COMMAND cd ${PROJECT_BINARY_DIR}/build_clang_cxx${CXX_STANDARD} && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure
         COMMENT "Compile and test with Clang for C++${CXX_STANDARD} (libc++)"
     )
 endforeach()
@@ -444,7 +450,7 @@ add_custom_target(ci_cppcheck
     COMMAND venv_cppcheck/bin/cppcheck --enable=warning --check-level=exhaustive --inline-suppr --inconclusive --force
             --std=c++11 ${PROJECT_SOURCE_DIR}/include/nlohmann/json.hpp -I ${CMAKE_SOURCE_DIR}/include
             --error-exitcode=1 --relative-paths=${PROJECT_SOURCE_DIR} -j ${N} --include=default_defines.hpp
-            --cppcheck-build-dir=cppcheck
+            --cppcheck-build-dir=cppcheck --check-level=exhaustive
             -UJSON_CATCH_USER -UJSON_TRY_USER -UJSON_ASSERT -UJSON_INTERNAL_CATCH -UJSON_THROW
             -DJSON_HAS_CPP_11 -UJSON_HAS_CPP_14 -UJSON_HAS_CPP_17 -UJSON_HAS_CPP_20 -UJSON_HAS_THREE_WAY_COMPARISON
     COMMENT "Check code with Cppcheck"
@@ -462,6 +468,34 @@ add_custom_target(ci_cpplint
     WORKING_DIRECTORY ${PROJECT_BINARY_DIR}
 )
 
+###############################################################################
+# Check code with OCLint.
+###############################################################################
+
+file(COPY ${PROJECT_SOURCE_DIR}/single_include/nlohmann/json.hpp DESTINATION ${PROJECT_BINARY_DIR}/src_single)
+file(RENAME ${PROJECT_BINARY_DIR}/src_single/json.hpp ${PROJECT_BINARY_DIR}/src_single/all.cpp)
+file(APPEND "${PROJECT_BINARY_DIR}/src_single/all.cpp" "\n\nint main()\n{}\n")
+
+add_executable(single_all ${PROJECT_BINARY_DIR}/src_single/all.cpp)
+target_compile_features(single_all PRIVATE cxx_std_11)
+
+add_custom_target(ci_oclint
+    COMMAND ${CMAKE_COMMAND}
+        -DCMAKE_BUILD_TYPE=Debug
+        -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
+        -DJSON_BuildTests=OFF -DJSON_CI=ON
+        -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_oclint
+    COMMAND ${OCLINT_TOOL} -i ${PROJECT_BINARY_DIR}/build_oclint/src_single/all.cpp -p ${PROJECT_BINARY_DIR}/build_oclint --
+        -report-type html -enable-global-analysis --max-priority-1=0 --max-priority-2=1000 --max-priority-3=2000
+        --disable-rule=MultipleUnaryOperator
+        --disable-rule=DoubleNegative
+        --disable-rule=ShortVariableName
+        --disable-rule=GotoStatement
+        --disable-rule=LongLine
+        -o ${PROJECT_BINARY_DIR}/build_oclint/oclint_report.html
+    COMMENT "Check code with OCLint"
+)
+
 ###############################################################################
 # Check code with Clang-Tidy.
 ###############################################################################
@@ -476,6 +510,21 @@ add_custom_target(ci_clang_tidy
     COMMENT "Check code with Clang-Tidy"
 )
 
+###############################################################################
+# Check code with PVS-Studio Analyzer <https://www.viva64.com/en/pvs-studio/>.
+###############################################################################
+
+add_custom_target(ci_pvs_studio
+    COMMAND CXX=${CLANG_TOOL} ${CMAKE_COMMAND}
+        -DCMAKE_BUILD_TYPE=Debug
+        -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
+        -DJSON_BuildTests=ON
+        -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_pvs_studio
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_pvs_studio && ${PVS_STUDIO_ANALYZER_TOOL} analyze -j 10
+    COMMAND cd ${PROJECT_BINARY_DIR}/build_pvs_studio && ${PLOG_CONVERTER_TOOL} -a'GA:1,2;64:1;CS' -t fullhtml PVS-Studio.log -o pvs
+    COMMENT "Check code with PVS Studio"
+)
+
 ###############################################################################
 # Check code with Infer <https://fbinfer.com> static analyzer.
 ###############################################################################
@@ -583,8 +632,7 @@ add_custom_target(ci_benchmarks
 # we test the project with different CMake versions:
 # - CMake 3.5 (the earliest supported)
 # - CMake 3.31.6 (the latest 3.x release)
-# - CMake 4.0.0 (the first 4.x release)
-# - the CMake version running this build (usually the latest release)
+# - CMake 4.0.0 (the latest release)
 
 function(ci_get_cmake version var)
     set(${var} ${PROJECT_BINARY_DIR}/cmake-${version}/bin/cmake)
@@ -608,24 +656,30 @@ ci_get_cmake(4.0.0  CMAKE_4_0_0_BINARY)
 
 # the tests require CMake 3.13 or later, so they are excluded for CMake 3.5.0
 set(JSON_CMAKE_FLAGS_3_5_0 JSON_Diagnostics JSON_Diagnostic_Positions JSON_GlobalUDLs JSON_ImplicitConversions JSON_DisableEnumSerialization
-    JSON_LegacyDiscardedValueComparison JSON_Install JSON_MultipleHeaders JSON_SystemInclude JSON_Valgrind
-    JSON_StrictNulHandling)
-set(JSON_CMAKE_FLAGS_3_31_6 JSON_BuildTests ${JSON_CMAKE_FLAGS_3_5_0})
+    JSON_LegacyDiscardedValueComparison JSON_Install JSON_MultipleHeaders JSON_SystemInclude JSON_Valgrind)
+set(JSON_CMAKE_FLAGS_3_31_6 JSON_BuildTests ${JSON_CMAKE_FLAGS_3_31_6})
 set(JSON_CMAKE_FLAGS_4_0_0 JSON_BuildTests ${JSON_CMAKE_FLAGS_3_5_0})
 
 function(ci_add_cmake_flags_targets flag min_version)
     string(TOLOWER "ci_cmake_flag_${flag}" flag_target)
     string(REPLACE . _ min_version_var ${min_version})
     set(cmake_binary ${CMAKE_${min_version_var}_BINARY})
+    add_custom_target(${flag_target}_${min_version}_2
+        COMMENT "Check CMake flag ${flag} (CMake ${CMAKE_VERSION})"
+        COMMAND ${CMAKE_COMMAND}
+            -Werror=dev
+            -D${flag}=ON
+            -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_${flag_target}
+    )
     add_custom_target(${flag_target}_${min_version_var}
-        COMMENT "Check CMake flag ${flag} (CMake ${min_version})"
+        COMMENT "Check CMake flag ${JSON_CMAKE_FLAG} (CMake ${min_version})"
         COMMAND mkdir -pv ${PROJECT_BINARY_DIR}/build_${flag_target}_${min_version_var}
         COMMAND cd ${PROJECT_BINARY_DIR}/build_${flag_target}_${min_version_var}
             && ${cmake_binary} -Werror=dev ${PROJECT_SOURCE_DIR} -D${flag}=ON
         DEPENDS ${cmake_binary}
     )
-    list(APPEND JSON_CMAKE_FLAG_TARGETS ${flag_target}_${min_version_var})
-    list(APPEND JSON_CMAKE_FLAG_BUILD_DIRS ${PROJECT_BINARY_DIR}/build_${flag_target}_${min_version_var})
+    list(APPEND JSON_CMAKE_FLAG_TARGETS ${JSON_CMAKE_FLAG_TARGET} ${flag_target}_${min_version_var})
+    list(APPEND JSON_CMAKE_FLAG_BUILD_DIRS ${PROJECT_BINARY_DIR}/build_${flag_target} ${PROJECT_BINARY_DIR}/build_${flag_target}_${min_version_var})
     set(JSON_CMAKE_FLAG_TARGETS ${JSON_CMAKE_FLAG_TARGETS} PARENT_SCOPE)
     set(JSON_CMAKE_FLAG_BUILD_DIRS ${JSON_CMAKE_FLAG_BUILD_DIRS} PARENT_SCOPE)
 endfunction()
@@ -642,20 +696,6 @@ foreach(JSON_CMAKE_FLAG ${JSON_CMAKE_FLAGS_4_0_0})
     ci_add_cmake_flags_targets(${JSON_CMAKE_FLAG} 4.0.0)
 endforeach()
 
-# check the same flags with the CMake version running this build
-foreach(JSON_CMAKE_FLAG ${JSON_CMAKE_FLAGS_4_0_0})
-    string(TOLOWER "ci_cmake_flag_${JSON_CMAKE_FLAG}" flag_target)
-    add_custom_target(${flag_target}
-        COMMENT "Check CMake flag ${JSON_CMAKE_FLAG} (CMake ${CMAKE_VERSION})"
-        COMMAND ${CMAKE_COMMAND}
-            -Werror=dev
-            -D${JSON_CMAKE_FLAG}=ON
-            -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_${flag_target}
-    )
-    list(APPEND JSON_CMAKE_FLAG_TARGETS ${flag_target})
-    list(APPEND JSON_CMAKE_FLAG_BUILD_DIRS ${PROJECT_BINARY_DIR}/build_${flag_target})
-endforeach()
-
 add_custom_target(ci_cmake_flags
     DEPENDS ${JSON_CMAKE_FLAG_TARGETS}
     COMMENT "Check CMake flags"
@@ -814,6 +854,6 @@ add_custom_target(ci_test_build_documentation
 ###############################################################################
 
 add_custom_target(ci_clean
-    COMMAND rm -fr ${PROJECT_BINARY_DIR}/build_* ${PROJECT_BINARY_DIR}/cmake-3.5.0 ${PROJECT_BINARY_DIR}/cmake-3.31.6 ${PROJECT_BINARY_DIR}/cmake-4.0.0 ${JSON_CMAKE_FLAG_BUILD_DIRS} ${single_binaries}
+    COMMAND rm -fr ${PROJECT_BINARY_DIR}/build_* cmake-3.5.0-Darwin64 ${JSON_CMAKE_FLAG_BUILD_DIRS} ${single_binaries}
     COMMENT "Clean generated directories"
 )

docs/mkdocs/docs/api/basic_json/parser_callback_t.md

@@ -100,3 +100,6 @@ the latter case, it is skipped completely, or replaced by `null` if it is the to
 - Added in version 1.0.0.
 - Fixed in version 3.13.0 to also remove discarded values from a parent object; before, discarding an array or a value
   stored under an object key left a discarded member behind, which made the parse result serialize to invalid JSON.
+- Fixed in version 3.13.0 so that discarding an array or object at its start event also hides its content from the
+  callback, as documented above; before, the callback was still called for the content, and the key of every member of
+  a discarded object was kept in memory until the parse ended.

docs/mkdocs/docs/community/quality_assurance.md

@@ -90,7 +90,7 @@ Note: Some modern features (like C++20 ranges or filesystem support) may be disa
         | GNU 14.2.0                                   | x86_64       | Ubuntu 22.04.1 LTS                | GitHub    |
         | GNU 15.1.0                                   | x86_64       | Ubuntu 22.04.1 LTS                | GitHub    |
         | GNU 16.1.0                                   | x86_64       | Ubuntu 22.04.1 LTS                | GitHub    |
-        | GNU 16.1.0                                   | arm64        | Ubuntu 24.04                      | GitHub    |
+        | GNU 16.1.0                                   | arm64        | Linux 6.1.100                     | Cirrus CI |
         | icpc (ICC) 2021.10.0 20230609                | x86_64       | Ubuntu 22.04 LTS                  | GitHub    |
         | icpx (Intel oneAPI DPC++/C++) 2025.3.2       | x86_64       | Ubuntu 24.04 LTS                  | GitHub    |
         | nvc++ (NVIDIA HPC SDK) 25.5-0                | x86_64       | Ubuntu 22.04 LTS                  | GitHub    |
@@ -132,8 +132,7 @@ Note: Some modern features (like C++20 ranges or filesystem support) may be disa
   [libstdc++](https://gcc.gnu.org/onlinedocs/libstdc++/) to detect subtle differences or incompatibilities.
 - [x] The code checked with [Include What You Use (IWYU)](https://include-what-you-use.org) that all required standard
   headers are included.
-- [x] On Windows, the library is compiled with `<Windows.h>` being included to detect and avoid common bugs (see
-  [`unit-windows_h.cpp`](https://github.com/nlohmann/json/blob/develop/tests/src/unit-windows_h.cpp)).
+- [x] On Windows, the library is compiled with `<Windows.h>` being included to detect and avoid common bugs.
 - [x] The library is compiled with exceptions disabled to support alternative means of error handling.
 
 ## Stable public API

include/nlohmann/detail/input/json_sax.hpp

@@ -582,8 +582,8 @@ class json_sax_dom_callback_parser
 
     bool start_object(std::size_t len)
     {
-        // check callback for object start
-        const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::object_start, discarded);
+        // check callback for object start; not called inside a discarded container
+        const bool keep = keep_stack.back() && callback(static_cast<int>(ref_stack.size()), parse_event_t::object_start, discarded);
         keep_stack.push_back(keep);
 
         // the key this object will be stored under, read before handle_value()
@@ -619,6 +619,18 @@ class json_sax_dom_callback_parser
 
     bool key(string_t& val)
     {
+        if (!keep_stack.back() || !ref_stack.back())
+        {
+            // the object is not stored: the value of this key is dropped in
+            // handle_value() without touching the key stacks
+            if (keep_stack.back())
+            {
+                BasicJsonType k = BasicJsonType(val);
+                static_cast<void>(callback(static_cast<int>(ref_stack.size()), parse_event_t::key, k));
+            }
+            return true;
+        }
+
         BasicJsonType k = BasicJsonType(val);
 
         // check callback for the key
@@ -704,7 +716,7 @@ class json_sax_dom_callback_parser
 
     bool start_array(std::size_t len)
     {
-        const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::array_start, discarded);
+        const bool keep = keep_stack.back() && callback(static_cast<int>(ref_stack.size()), parse_event_t::array_start, discarded);
         keep_stack.push_back(keep);
 
         // see start_object()

single_include/nlohmann/json.hpp

@@ -11996,8 +11996,8 @@ class json_sax_dom_callback_parser
 
     bool start_object(std::size_t len)
     {
-        // check callback for object start
-        const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::object_start, discarded);
+        // check callback for object start; not called inside a discarded container
+        const bool keep = keep_stack.back() && callback(static_cast<int>(ref_stack.size()), parse_event_t::object_start, discarded);
         keep_stack.push_back(keep);
 
         // the key this object will be stored under, read before handle_value()
@@ -12033,6 +12033,18 @@ class json_sax_dom_callback_parser
 
     bool key(string_t& val)
     {
+        if (!keep_stack.back() || !ref_stack.back())
+        {
+            // the object is not stored: the value of this key is dropped in
+            // handle_value() without touching the key stacks
+            if (keep_stack.back())
+            {
+                BasicJsonType k = BasicJsonType(val);
+                static_cast<void>(callback(static_cast<int>(ref_stack.size()), parse_event_t::key, k));
+            }
+            return true;
+        }
+
         BasicJsonType k = BasicJsonType(val);
 
         // check callback for the key
@@ -12118,7 +12130,7 @@ class json_sax_dom_callback_parser
 
     bool start_array(std::size_t len)
     {
-        const bool keep = callback(static_cast<int>(ref_stack.size()), parse_event_t::array_start, discarded);
+        const bool keep = keep_stack.back() && callback(static_cast<int>(ref_stack.size()), parse_event_t::array_start, discarded);
         keep_stack.push_back(keep);
 
         // see start_object()

tests/src/unit-class_parser.cpp

@@ -1966,6 +1966,102 @@ TEST_CASE("parser class")
             }
         }
 
+        SECTION("no callback for the content of a discarded container (#5643)")
+        {
+            // discarding a container at its start event must also hide
+            // everything inside it from the callback: none of the nested
+            // keys, values, or nested containers' own start/end events may
+            // be reported
+            std::vector<std::string> log;
+            bool first = true;
+            const json j = json::parse(R"({"skip": {"k1": 1, "k2": [2, {"k3": 3}]}, "keep": 1})",
+                                       [&](int depth, json::parse_event_t event, json & parsed)
+            {
+                static const char* const names[] = {"object_start", "object_end", "array_start", "array_end", "key", "value"};
+                log.push_back(std::to_string(depth) + " " + names[static_cast<int>(event)] + " " + parsed.dump());
+
+                if (depth == 1 && event == json::parse_event_t::object_start && first)
+                {
+                    // discard "skip" right at its object_start event
+                    first = false;
+                    return false;
+                }
+                return true;
+            });
+
+            CHECK(log == std::vector<std::string>
+            {
+                "0 object_start <discarded>",
+                "1 key \"skip\"",
+                "1 object_start <discarded>",
+                "1 key \"keep\"",
+                "1 value 1",
+                "0 object_end {\"keep\":1}"
+            });
+            CHECK(j == json({{"keep", 1}}));
+        }
+
+        SECTION("callback still called inside a container whose key was rejected (#5643)")
+        {
+            // rejecting a key does not discard its value's container at the
+            // container's own start event, so the callback is still called
+            // for that container's content; only storing the container
+            // under the rejected key is skipped
+            // (documented for parser_callback_t: "the callback is still
+            // called for the associated value, but its return value has no
+            // further effect")
+            const auto record = [](std::vector<std::string>& log, int depth, json::parse_event_t event, const json & parsed)
+            {
+                static const char* const names[] = {"object_start", "object_end", "array_start", "array_end", "key", "value"};
+                log.push_back(std::to_string(depth) + " " + names[static_cast<int>(event)] + " " + parsed.dump());
+            };
+
+            std::vector<std::string> log_object;
+            const json j_object = json::parse(R"({"skip": {"k1": 1}, "keep": 2})",
+                                              [&](int depth, json::parse_event_t event, json & parsed)
+            {
+                record(log_object, depth, event, parsed);
+                return !(event == json::parse_event_t::key && parsed == json("skip"));
+            });
+
+            CHECK(log_object == std::vector<std::string>
+            {
+                "0 object_start <discarded>",
+                "1 key \"skip\"",
+                "1 object_start <discarded>",
+                "2 key \"k1\"",
+                "2 value 1",
+                "1 key \"keep\"",
+                "1 value 2",
+                "0 object_end {\"keep\":2}"
+            });
+            CHECK(j_object == json({{"keep", 2}}));
+
+            // same for a rejected key whose value is an array rather than an object
+            std::vector<std::string> log_array;
+            const json j_array = json::parse(R"({"skip": [1, {"k1": 2}], "keep": 2})",
+                                             [&](int depth, json::parse_event_t event, json & parsed)
+            {
+                record(log_array, depth, event, parsed);
+                return !(event == json::parse_event_t::key && parsed == json("skip"));
+            });
+
+            CHECK(log_array == std::vector<std::string>
+            {
+                "0 object_start <discarded>",
+                "1 key \"skip\"",
+                "1 array_start <discarded>",
+                "2 value 1",
+                "2 object_start <discarded>",
+                "3 key \"k1\"",
+                "3 value 2",
+                "1 key \"keep\"",
+                "1 value 2",
+                "0 object_end {\"keep\":2}"
+            });
+            CHECK(j_array == json({{"keep", 2}}));
+        }
+
         SECTION("special cases")
         {
             // the following test cases cover the situation in which an empty

tests/src/unit.cpp

@@ -7,22 +7,4 @@
 // SPDX-License-Identifier: MIT
 
 #define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
-
-// libc++ annotates std::mutex for Clang's thread safety analysis, so -Weverything
-// reports -Wthread-safety-negative for the locks in doctest's reporters, which are
-// only compiled in this file. __has_warning keeps older Clang versions from
-// reporting an unknown warning group.
-#if defined(__clang__) && defined(__has_warning)
-    #if __has_warning("-Wthread-safety-negative")
-        #pragma clang diagnostic push
-        #pragma clang diagnostic ignored "-Wthread-safety-negative"
-    #endif
-#endif
-
 #include "doctest_compatibility.h"
-
-#if defined(__clang__) && defined(__has_warning)
-    #if __has_warning("-Wthread-safety-negative")
-        #pragma clang diagnostic pop
-    #endif
-#endif

tools/astyle/requirements.txt

@@ -1,4 +1 @@
-# astyle is deliberately pinned: newer versions reformat the code, and this version
-# defines the formatting that `make amalgamate` produces and check_amalgamation.yml enforces.
-# Dependabot is told to ignore it in .github/dependabot.yml.
 astyle==3.4.13