Merge ci/path-filters

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Merge develop
2026-10-28 16:55:41 +00:00 · 2026-10-28 07:11:44 +01:00 · 2026-10-28 07:11:43 +01:00 · 2026-10-27 19:40:21 +01:00 · 2026-10-27 19:39:20 +01:00 · 2026-10-27 18:58:36 +01:00
16 changed files with 1374 additions and 629 deletions
@@ -154,6 +154,15 @@ and each page's title (H1) and declaration by
 [`docs/docset/generate_docset.py`](https://github.com/nlohmann/json/blob/develop/docs/docset/generate_docset.py);
 `make build` reports API pages that cannot be classified.

+A pull request that changes only the documentation, Markdown files, GitHub metadata, or license files skips the
+compiler workflows (Ubuntu, macOS, Windows); the documentation and license checks still run. See
+[`tools/check_path_filters`](https://github.com/nlohmann/json/tree/develop/tools/check_path_filters) for the list of
+skipped files and what to do when a compiler job starts reading one of them.
+
+Most compiler jobs run only once a maintainer adds the label "🚀 ready to merge" to a pull request; until then, a
+smaller set of jobs runs on every push. See
+[How CI runs](https://json.nlohmann.me/community/quality_assurance/#how-ci-runs) for the sets and when they run.
+
 ### Amalgamate the source code

 The single-header files
@@ -7,6 +7,25 @@ on:
      - master
      - release/*
  pull_request:
+    # Skip pull requests that change only files no job here reads. The list is checked by
+    # tools/check_path_filters/check_path_filters.py (repository_checks.yml); change both together.
+    paths:
+      - '**'
+      - '!docs/**'
+      - '!**.md'
+      - '!.github/*'
+      - '!.github/ISSUE_TEMPLATE/**'
+      - '!.github/external_ci/**'
+      - '!.github/workflows/**'
+      - '!.reuse/**'
+      - '!LICENSES/**'
+      - '!CITATION.cff'
+      - '!REUSE.toml'
+      # read by tools/check_build_options in the ci_meson_install job (ubuntu.yml)
+      - 'docs/mkdocs/docs/integration/package_managers.md'
+      # built by the swiftpm job (macos.yml)
+      - 'docs/mkdocs/docs/integration/swift/**'
+      - '.github/workflows/macos.yml'
  workflow_dispatch:

 concurrency:
@@ -0,0 +1,83 @@
+name: Repository checks
+
+# Checks that concern files the compiler workflows (ubuntu.yml, macos.yml,
+# windows.yml) skip with their path filter: the documentation, the license
+# information, and the CI configuration itself. This workflow has no path filter.
+on:
+  push:
+    branches:
+      - develop
+      - master
+      - release/*
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  check_ci_configuration:
+    runs-on: ubuntu-26.04
+    steps:
+      - name: Harden Runner
+        uses: step-security/harden-runner@ccd8616d44fd3846e67624a50d5aad6d37bf2d25 # v2.22.1
+        with:
+          egress-policy: audit
+
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Check the path filters of the compiler workflows
+        run: python3 tools/check_path_filters/check_path_filters.py
+      - name: Check the job sets of the compiler workflows and their documentation
+        run: |
+          python3 -m venv venv
+          venv/bin/pip install --quiet -r tools/ci_jobs/requirements.txt
+          venv/bin/python tools/ci_jobs/ci_jobs.py
+
+  ci_reuse_compliance:
+    runs-on: ubuntu-26.04
+    steps:
+      - name: Harden Runner
+        uses: step-security/harden-runner@ccd8616d44fd3846e67624a50d5aad6d37bf2d25 # v2.22.1
+        with:
+          egress-policy: audit
+
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Get latest CMake and ninja
+        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+      - name: Run CMake
+        run: cmake -S . -B build -DJSON_CI=On
+      - name: Build
+        run: cmake --build build --target ci_reuse_compliance
+
+  ci_test_documentation:
+    runs-on: ubuntu-26.04
+    strategy:
+      matrix:
+        target: [ci_test_examples, ci_test_build_documentation, ci_test_documentation_mermaid]
+    steps:
+      - name: Harden Runner
+        uses: step-security/harden-runner@ccd8616d44fd3846e67624a50d5aad6d37bf2d25 # v2.22.1
+        with:
+          egress-policy: audit
+
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+          # the git-revision-date-localized plugin needs the history; a shallow clone makes the strict build fail
+          fetch-depth: ${{ matrix.target == 'ci_test_build_documentation' && '0' || '1' }}
+      - uses: actions/setup-node@949feb2413d6458794dcd2491c4babbbce0c15c1 # v7.1.0
+        if: matrix.target == 'ci_test_documentation_mermaid'
+        with:
+          node-version: 24
+      - name: Run CMake
+        run: cmake -S . -B build -DJSON_CI=On
+      - name: Build
+        run: cmake --build build --target ${{ matrix.target }}
@@ -7,17 +7,62 @@ on:
      - master
      - release/*
  pull_request:
+    # labeled: the "🚀 ready to merge" label starts the full set (see below)
+    types: [opened, synchronize, reopened, labeled]
+    # Skip pull requests that change only files no job here reads. The list is checked by
+    # tools/check_path_filters/check_path_filters.py (repository_checks.yml); change both together.
+    paths:
+      - '**'
+      - '!docs/**'
+      - '!**.md'
+      - '!.github/*'
+      - '!.github/ISSUE_TEMPLATE/**'
+      - '!.github/external_ci/**'
+      - '!.github/workflows/**'
+      - '!.reuse/**'
+      - '!LICENSES/**'
+      - '!CITATION.cff'
+      - '!REUSE.toml'
+      # read by tools/check_build_options in the ci_meson_install job (ubuntu.yml)
+      - 'docs/mkdocs/docs/integration/package_managers.md'
+      # built by the swiftpm job (macos.yml)
+      - 'docs/mkdocs/docs/integration/swift/**'
+      - '.github/workflows/ubuntu.yml'
+  schedule:
+    # the nightly set (see below), on develop
+    - cron: '0 2 * * *'
  workflow_dispatch:

 permissions:
  contents: read

+# A run triggered by any other label gets a group of its own, so it does not
+# cancel the run of the last push; its jobs are skipped.
 concurrency:
-  group: ${{ github.workflow }}-${{ github.ref || github.run_id }}
+  group: ${{ github.workflow }}-${{ github.event_name == 'schedule' && 'nightly' || github.ref || github.run_id }}${{ github.event.action == 'labeled' && github.event.label.name != '🚀 ready to merge' && format('-{0}', github.run_id) || '' }}
  cancel-in-progress: true

+# The jobs are split into three sets (see "How CI runs" in
+# docs/mkdocs/docs/community/quality_assurance.md):
+#
+# - PR set: every pull request push and every push; chosen because these jobs
+#   caught 92 % of the failing commits in Sep/Oct 2026.
+# - full set: after the PR set passed, on pushes and on pull requests with the
+#   "🚀 ready to merge" label; every remaining compiler, version and standard.
+# - nightly set: slow tools and rare compilers, nightly on develop, on pushes
+#   to master and release/*, and when started by hand.
+#
+# A matrix whose entries belong to different sets is split into one job per
+# set; the jobs share their steps through YAML anchors. tools/ci_jobs checks
+# that every job belongs to exactly one set.
+
 jobs:
+  ###########################################################################
+  # PR set
+  ###########################################################################
+
  ci_test_gcc:
+    if: &pr_set ${{ github.event_name != 'schedule' && (github.event.action != 'labeled' || github.event.label.name == '🚀 ready to merge') }}
    runs-on: ubuntu-latest
    container: gcc:latest
    steps:
@@ -32,6 +77,7 @@ jobs:
        run: cmake --build build --target ci_test_gcc

  ci_meson_install:
+    if: *pr_set
    runs-on: ubuntu-26.04
    steps:
      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -76,7 +122,342 @@ jobs:
          cmake -S tests/cmake_import/project -B build-import-split -DCMAKE_PREFIX_PATH=${{ github.workspace }}/install-split
          cmake --build build-import-split

+  ci_static_analysis_ubuntu:
+    if: *pr_set
+    runs-on: ubuntu-26.04
+    strategy:
+      matrix:
+        target: [ci_cpplint]
+    steps: &static_analysis_ubuntu_steps
+      - name: Harden Runner
+        uses: step-security/harden-runner@ccd8616d44fd3846e67624a50d5aad6d37bf2d25 # v2.22.1
+        with:
+          egress-policy: audit
+
+      - name: Install Valgrind
+        if: matrix.target == 'ci_test_valgrind'
+        run: sudo apt-get update ; sudo apt-get install -y valgrind
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Get latest CMake and ninja
+        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+      - name: Run CMake
+        run: cmake -S . -B build -DJSON_CI=On
+      - name: Build
+        run: cmake --build build --target ${{ matrix.target }}
+
+  ci_static_analysis_clang:
+    if: *pr_set
+    runs-on: ubuntu-latest
+    container: silkeh/clang:22
+    strategy:
+      matrix:
+        target: [ci_test_clang, ci_clang_tidy, ci_test_clang_sanitizer, ci_single_binaries]
+    steps: &static_analysis_clang_steps
+      - name: Install git, clang-tools, iwyu (ci_single_binaries), and unzip
+        run: apt-get update ; apt-get install -y git clang-tools iwyu unzip
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Get latest CMake and ninja
+        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+      - name: Run CMake
+        run: cmake -S . -B build -DJSON_CI=On
+      - name: Build
+        run: cmake --build build --target ${{ matrix.target }}
+
+  ci_cmake_options:
+    if: *pr_set
+    runs-on: ubuntu-latest
+    container: ubuntu:24.04
+    strategy:
+      matrix:
+        target: [ci_test_diagnostics, ci_test_diagnostic_positions, ci_test_noexceptions, ci_test_noglobaludls]
+    steps: &cmake_options_steps
+      - name: Install build-essential
+        run: apt-get update ; apt-get install -y build-essential unzip wget git
+      # the CMake 3.5.0 release binary that ci_cmake_flags downloads links
+      # against libidn.so.11, which Ubuntu 24.04 no longer ships
+      - name: Install libidn11 for CMake 3.5.0
+        if: matrix.target == 'ci_cmake_flags'
+        run: |
+          wget -q http://archive.ubuntu.com/ubuntu/pool/main/libi/libidn/libidn11_1.33-2.2ubuntu2_amd64.deb
+          dpkg -i libidn11_1.33-2.2ubuntu2_amd64.deb
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Get latest CMake and ninja
+        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+      - name: Run CMake
+        run: cmake -S . -B build -DJSON_CI=On
+      - name: Build
+        run: cmake --build build --target ${{ matrix.target }}
+
+  ci_test_compilers_gcc_old:
+    if: *pr_set
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        compiler: ['4.8']
+    # official gcc:4.8/4.9/5/6 images fail to check out code (too old for
+    # actions/checkout); install the old compilers on top of official ubuntu:20.04
+    # instead, mirroring what the (now retired) custom json-ci image did.
+    container: ubuntu:20.04
+    steps: &compilers_gcc_old_steps
+      - name: Install g++-${{ matrix.compiler }}
+        run: |
+          export DEBIAN_FRONTEND=noninteractive
+          apt-get update
+          apt-get install -y --no-install-recommends software-properties-common ca-certificates gnupg make git
+          # add-apt-repository resolves the PPA through the Launchpad API,
+          # which intermittently times out or fails the team lookup (the plain
+          # "deb ..." sources below never hit Launchpad and never flake).
+          # Retry with backoff so a transient Launchpad blip does not fail CI.
+          for attempt in 1 2 3 4 5; do
+            add-apt-repository -y ppa:ubuntu-toolchain-r/test && break
+            echo "::warning::add-apt-repository ppa:ubuntu-toolchain-r/test failed (attempt ${attempt}/5); retrying"
+            sleep $((attempt * 10))
+          done
+          apt-add-repository -y "deb http://archive.ubuntu.com/ubuntu/ bionic main"
+          apt-add-repository -y "deb http://archive.ubuntu.com/ubuntu/ bionic universe"
+          apt-add-repository -y "deb http://archive.ubuntu.com/ubuntu/ xenial main"
+          apt-add-repository -y "deb http://archive.ubuntu.com/ubuntu/ xenial universe"
+          apt-add-repository -y "deb http://archive.ubuntu.com/ubuntu/ xenial-updates main"
+          apt-add-repository -y "deb http://archive.ubuntu.com/ubuntu/ xenial-updates universe"
+          apt-get update
+          apt-get install -y --no-install-recommends g++-${{ matrix.compiler }}
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Get latest CMake and ninja
+        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+      - name: Run CMake
+        run: CXX=g++-${{ matrix.compiler }} cmake -S . -B build -DJSON_CI=On
+      - name: Build
+        run: cmake --build build --target ci_test_compiler_g++-${{ matrix.compiler }}
+
+  ci_test_compilers_clang:
+    if: *pr_set
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        compiler: ['3.4']
+    container: silkeh/clang:${{ matrix.compiler }}
+    steps: &compilers_clang_steps
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Get latest CMake and ninja
+        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+      - name: Disable filesystem support (std::filesystem is unusable) for clang 7 / 8 / 9 / 10
+        run: echo "JSON_FORCED_GLOBAL_COMPILE_OPTIONS=-DJSON_HAS_FILESYSTEM=0;-DJSON_HAS_EXPERIMENTAL_FILESYSTEM=0" >> "$GITHUB_ENV"
+        if: ${{ matrix.compiler == '7' || matrix.compiler == '8' || matrix.compiler == '9' || matrix.compiler == '10' }}
+      - name: Run CMake
+        run: cmake -S . -B build -DJSON_CI=On
+      - name: Build
+        run: cmake --build build --target ci_test_compiler_default
+
+  ci_test_standards_gcc:
+    if: *pr_set
+    runs-on: ubuntu-latest
+    container: gcc:latest
+    strategy:
+      matrix:
+        standard: [26]
+    steps: &standards_gcc_steps
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Get latest CMake and ninja
+        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+      - name: Run CMake
+        run: cmake -S . -B build -DJSON_CI=On
+      - name: Build
+        run: cmake --build build --target ci_test_gcc_cxx${{ matrix.standard }}
+
+  ci_test_standards_clang:
+    if: *pr_set
+    runs-on: ubuntu-latest
+    container: silkeh/clang:latest
+    strategy:
+      matrix:
+        standard: [26]
+        stdlib: [libcxx]
+    steps: &standards_clang_steps
+      - name: Install git and unzip
+        run: apt-get update ; apt-get install -y git unzip
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Get latest CMake and ninja
+        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+      - name: Run CMake
+        run: cmake -S . -B build -DJSON_CI=On
+      - name: Build with libc++
+        run: cmake --build build --target ci_test_clang_libcxx_cxx${{ matrix.standard }}
+        if: ${{ matrix.stdlib == 'libcxx' }}
+      - name: Build with libstdc++
+        run: cmake --build build --target ci_test_clang_cxx${{ matrix.standard }}
+        if: ${{ matrix.stdlib == 'libstdcxx' }}
+
+  ci_emscripten:
+    if: *pr_set
+    runs-on: ubuntu-26.04
+    steps:
+      - name: Harden Runner
+        uses: step-security/harden-runner@ccd8616d44fd3846e67624a50d5aad6d37bf2d25 # v2.22.1
+        with:
+          egress-policy: audit
+
+      - name: Install emscripten
+        uses: mymindstorm/setup-emsdk@4528d102f7230f0e7b276855c01ea1159be0e984 # v16
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Get latest CMake and ninja
+        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+      - name: Run CMake
+        run: cmake -S . -B build -DCMAKE_TOOLCHAIN_FILE=$EMSDK/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake -GNinja
+      - name: Build
+        run: cmake --build build
+
+  ###########################################################################
+  # full set: starts after the PR set passed
+  ###########################################################################
+
+  ci_static_analysis_ubuntu_full:
+    needs: &pr_set_jobs [ci_test_gcc, ci_meson_install, ci_static_analysis_ubuntu, ci_static_analysis_clang, ci_cmake_options, ci_test_compilers_gcc_old, ci_test_compilers_clang, ci_test_standards_gcc, ci_test_standards_clang, ci_emscripten]
+    if: &full_set ${{ github.event_name == 'push' || github.event_name == 'workflow_dispatch' || contains(github.event.pull_request.labels.*.name, '🚀 ready to merge') }}
+    runs-on: ubuntu-26.04
+    strategy:
+      matrix:
+        target: [ci_test_single_header, ci_cppcheck, ci_reproducible_tests, ci_non_git_tests, ci_offline_testdata]
+    steps: *static_analysis_ubuntu_steps
+
+  ci_static_analysis_clang_full:
+    needs: *pr_set_jobs
+    if: *full_set
+    runs-on: ubuntu-latest
+    container: silkeh/clang:22
+    strategy:
+      matrix:
+        target: [ci_clang_analyze]
+    steps: *static_analysis_clang_steps
+
+  ci_cmake_options_full:
+    needs: *pr_set_jobs
+    if: *full_set
+    runs-on: ubuntu-latest
+    container: ubuntu:24.04
+    strategy:
+      matrix:
+        target: [ci_cmake_flags, ci_test_noimplicitconversions, ci_test_legacycomparison, ci_test_disableenumserialization, ci_test_disabletuplereferenceconversion, ci_test_skiplibraryversioncheck, ci_test_simdutf, ci_test_strict_nul_handling, ci_test_delete_deprecated_functions, ci_test_no_thread_local]
+    steps: *cmake_options_steps
+
+  ci_test_compilers_gcc_old_full:
+    needs: *pr_set_jobs
+    if: *full_set
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        compiler: ['4.9', '5', '6']
+    container: ubuntu:20.04
+    steps: *compilers_gcc_old_steps
+
+  ci_test_compilers_gcc_full:
+    needs: *pr_set_jobs
+    if: *full_set
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        # older GCC docker images (4, 5, 6) fail to check out code
+        compiler: ['7', '8', '9', '10', '11', '12', '13', '14', '15', '16', 'latest']
+    container: gcc:${{ matrix.compiler }}
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Get latest CMake and ninja
+        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+      - name: Run CMake
+        run: cmake -S . -B build -DJSON_CI=On
+      - name: Build
+        run: cmake --build build --target ci_test_compiler_default
+
+  ci_test_compilers_clang_full:
+    needs: *pr_set_jobs
+    if: *full_set
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        compiler: ['3.5', '3.6', '3.7', '3.8', '3.9', '4', '5', '6', '7', '8', '9', '10', '11', '12', '13', '14', '15-bullseye', '16', '17', '18', '19', '20', '21', '22', 'latest']
+    container: silkeh/clang:${{ matrix.compiler }}
+    steps: *compilers_clang_steps
+
+  ci_test_standards_gcc_full:
+    needs: *pr_set_jobs
+    if: *full_set
+    runs-on: ubuntu-latest
+    container: gcc:latest
+    strategy:
+      matrix:
+        standard: [11, 14, 17, 20, 23]
+    steps: *standards_gcc_steps
+
+  ci_test_standards_clang_full:
+    needs: *pr_set_jobs
+    if: *full_set
+    runs-on: ubuntu-latest
+    container: silkeh/clang:latest
+    strategy:
+      matrix:
+        standard: [11, 14, 17, 20, 23, 26]
+        stdlib: [libcxx, libstdcxx]
+        exclude:
+          # in the PR set
+          - standard: 26
+            stdlib: libcxx
+    steps: *standards_clang_steps
+
+  ci_module_cpp20:
+    needs: *pr_set_jobs
+    if: *full_set
+    strategy:
+      matrix:
+        container: ['gcc:latest', 'silkeh/clang:latest']
+    runs-on: ubuntu-latest
+    container: ${{ matrix.container }}
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      # The module test uses `import std;`, which needs CMake's experimental
+      # import-std support. Its opt-in token is CMake-version-specific, so pin
+      # CMake to the version whose token is set in tests/module_cpp20/CMakeLists.txt.
+      - name: Get pinned CMake and ninja
+        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        with:
+          cmakeVersion: 4.3.4
+      # Clang: the std library module is provided by libc++ (the image's libstdc++
+      # ships none), and the image's libc++ module manifest has a broken relative
+      # path — repoint it at the real module sources.
+      - name: Use libc++ and fix its module manifest path (Clang)
+        if: matrix.container == 'silkeh/clang:latest'
+        run: |
+          echo "CXXFLAGS=-stdlib=libc++" >> "$GITHUB_ENV"
+          mkdir -p /usr/lib/share && ln -sf /usr/lib/llvm-*/share/libc++ /usr/lib/share/libc++
+      - name: Run CMake
+        run: cmake -S . -B build -DJSON_CI=On
+      - name: Build
+        run: cmake --build build --target ci_module_cpp20
+
+  ###########################################################################
+  # nightly set
+  ###########################################################################
+
  ci_infer:
+    if: &nightly_set ${{ github.event_name == 'schedule' || github.event_name == 'workflow_dispatch' || (github.event_name == 'push' && github.ref != 'refs/heads/develop') }}
    runs-on: ubuntu-26.04
    steps:
      - name: Harden Runner
@@ -105,76 +486,16 @@ jobs:
          path: ${{ github.workspace }}/build/build_infer/infer-out/report.txt
          if-no-files-found: ignore

-  ci_static_analysis_ubuntu:
+  ci_static_analysis_ubuntu_nightly:
+    if: *nightly_set
    runs-on: ubuntu-26.04
    strategy:
      matrix:
-        target: [ci_test_single_header, ci_cppcheck, ci_cpplint, ci_reproducible_tests, ci_non_git_tests, ci_offline_testdata, ci_reuse_compliance, ci_test_valgrind]
-    steps:
-      - name: Harden Runner
-        uses: step-security/harden-runner@ccd8616d44fd3846e67624a50d5aad6d37bf2d25 # v2.22.1
-        with:
-          egress-policy: audit
-
-      - name: Install Valgrind
-        if: matrix.target == 'ci_test_valgrind'
-        run: sudo apt-get update ; sudo apt-get install -y valgrind
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        with:
-          persist-credentials: false
-      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
-      - name: Run CMake
-        run: cmake -S . -B build -DJSON_CI=On
-      - name: Build
-        run: cmake --build build --target ${{ matrix.target }}
-
-  ci_static_analysis_clang:
-    runs-on: ubuntu-latest
-    container: silkeh/clang:22
-    strategy:
-      matrix:
-        target: [ci_test_clang, ci_clang_tidy, ci_test_clang_sanitizer, ci_clang_analyze, ci_single_binaries]
-    steps:
-      - name: Install git, clang-tools, iwyu (ci_single_binaries), and unzip
-        run: apt-get update ; apt-get install -y git clang-tools iwyu unzip
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        with:
-          persist-credentials: false
-      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
-      - name: Run CMake
-        run: cmake -S . -B build -DJSON_CI=On
-      - name: Build
-        run: cmake --build build --target ${{ matrix.target }}
-
-  ci_cmake_options:
-    runs-on: ubuntu-latest
-    container: ubuntu:24.04
-    strategy:
-      matrix:
-        target: [ci_cmake_flags, ci_test_diagnostics, ci_test_diagnostic_positions, ci_test_noexceptions, ci_test_noimplicitconversions, ci_test_legacycomparison, ci_test_noglobaludls, ci_test_disableenumserialization, ci_test_disabletuplereferenceconversion, ci_test_skiplibraryversioncheck, ci_test_simdutf, ci_test_strict_nul_handling, ci_test_delete_deprecated_functions, ci_test_no_thread_local]
-    steps:
-      - name: Install build-essential
-        run: apt-get update ; apt-get install -y build-essential unzip wget git
-      # the CMake 3.5.0 release binary that ci_cmake_flags downloads links
-      # against libidn.so.11, which Ubuntu 24.04 no longer ships
-      - name: Install libidn11 for CMake 3.5.0
-        if: matrix.target == 'ci_cmake_flags'
-        run: |
-          wget -q http://archive.ubuntu.com/ubuntu/pool/main/libi/libidn/libidn11_1.33-2.2ubuntu2_amd64.deb
-          dpkg -i libidn11_1.33-2.2ubuntu2_amd64.deb
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        with:
-          persist-credentials: false
-      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
-      - name: Run CMake
-        run: cmake -S . -B build -DJSON_CI=On
-      - name: Build
-        run: cmake --build build --target ${{ matrix.target }}
+        target: [ci_test_valgrind]
+    steps: *static_analysis_ubuntu_steps

  ci_test_coverage:
+    if: *nightly_set
    runs-on: ubuntu-26.04
    steps:
      - name: Harden Runner
@@ -208,128 +529,8 @@ jobs:
          path-to-lcov: ${{ github.workspace }}/build/json.info.filtered.noexcept
          fail-on-error: false

-  ci_test_compilers_gcc_old:
-    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        compiler: ['4.8', '4.9', '5', '6']
-    # official gcc:4.8/4.9/5/6 images fail to check out code (too old for
-    # actions/checkout); install the old compilers on top of official ubuntu:20.04
-    # instead, mirroring what the (now retired) custom json-ci image did.
-    container: ubuntu:20.04
-    steps:
-      - name: Install g++-${{ matrix.compiler }}
-        run: |
-          export DEBIAN_FRONTEND=noninteractive
-          apt-get update
-          apt-get install -y --no-install-recommends software-properties-common ca-certificates gnupg make git
-          # add-apt-repository resolves the PPA through the Launchpad API,
-          # which intermittently times out or fails the team lookup (the plain
-          # "deb ..." sources below never hit Launchpad and never flake).
-          # Retry with backoff so a transient Launchpad blip does not fail CI.
-          for attempt in 1 2 3 4 5; do
-            add-apt-repository -y ppa:ubuntu-toolchain-r/test && break
-            echo "::warning::add-apt-repository ppa:ubuntu-toolchain-r/test failed (attempt ${attempt}/5); retrying"
-            sleep $((attempt * 10))
-          done
-          apt-add-repository -y "deb http://archive.ubuntu.com/ubuntu/ bionic main"
-          apt-add-repository -y "deb http://archive.ubuntu.com/ubuntu/ bionic universe"
-          apt-add-repository -y "deb http://archive.ubuntu.com/ubuntu/ xenial main"
-          apt-add-repository -y "deb http://archive.ubuntu.com/ubuntu/ xenial universe"
-          apt-add-repository -y "deb http://archive.ubuntu.com/ubuntu/ xenial-updates main"
-          apt-add-repository -y "deb http://archive.ubuntu.com/ubuntu/ xenial-updates universe"
-          apt-get update
-          apt-get install -y --no-install-recommends g++-${{ matrix.compiler }}
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        with:
-          persist-credentials: false
-      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
-      - name: Run CMake
-        run: CXX=g++-${{ matrix.compiler }} cmake -S . -B build -DJSON_CI=On
-      - name: Build
-        run: cmake --build build --target ci_test_compiler_g++-${{ matrix.compiler }}
-
-  ci_test_compilers_gcc:
-    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        # older GCC docker images (4, 5, 6) fail to check out code
-        compiler: ['7', '8', '9', '10', '11', '12', '13', '14', '15', '16', 'latest']
-    container: gcc:${{ matrix.compiler }}
-    steps:
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        with:
-          persist-credentials: false
-      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
-      - name: Run CMake
-        run: cmake -S . -B build -DJSON_CI=On
-      - name: Build
-        run: cmake --build build --target ci_test_compiler_default
-
-  ci_test_compilers_clang:
-    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        compiler: ['3.4', '3.5', '3.6', '3.7', '3.8', '3.9', '4', '5', '6', '7', '8', '9', '10', '11', '12', '13', '14', '15-bullseye', '16', '17', '18', '19', '20', '21', '22', 'latest']
-    container: silkeh/clang:${{ matrix.compiler }}
-    steps:
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        with:
-          persist-credentials: false
-      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
-      - 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: ${{ matrix.compiler == '7' || matrix.compiler == '8' || matrix.compiler == '9' || matrix.compiler == '10' }}
-      - name: Run CMake
-        run: cmake -S . -B build -DJSON_CI=On
-      - name: Build
-        run: cmake --build build --target ci_test_compiler_default
-
-  ci_test_standards_gcc:
-    runs-on: ubuntu-latest
-    container: gcc:latest
-    strategy:
-      matrix:
-        standard: [11, 14, 17, 20, 23, 26]
-    steps:
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        with:
-          persist-credentials: false
-      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
-      - name: Run CMake
-        run: cmake -S . -B build -DJSON_CI=On
-      - name: Build
-        run: cmake --build build --target ci_test_gcc_cxx${{ matrix.standard }}
-
-  ci_test_standards_clang:
-    runs-on: ubuntu-latest
-    container: silkeh/clang:latest
-    strategy:
-      matrix:
-        standard: [11, 14, 17, 20, 23, 26]
-        stdlib: [libcxx, libstdcxx]
-    steps:
-      - name: Install git and unzip
-        run: apt-get update ; apt-get install -y git unzip
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        with:
-          persist-credentials: false
-      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
-      - name: Run CMake
-        run: cmake -S . -B build -DJSON_CI=On
-      - name: Build with libc++
-        run: cmake --build build --target ci_test_clang_libcxx_cxx${{ matrix.standard }}
-        if: ${{ matrix.stdlib == 'libcxx' }}
-      - name: Build with libstdc++
-        run: cmake --build build --target ci_test_clang_cxx${{ matrix.standard }}
-        if: ${{ matrix.stdlib == 'libstdcxx' }}
-
  ci_cuda_example:
+    if: *nightly_set
    runs-on: ubuntu-latest
    strategy:
      fail-fast: false
@@ -352,37 +553,8 @@ jobs:
      - name: Build
        run: cmake --build build --target ci_cuda_example

-  ci_module_cpp20:
-    strategy:
-      matrix:
-        container: ['gcc:latest', 'silkeh/clang:latest']
-    runs-on: ubuntu-latest
-    container: ${{ matrix.container }}
-    steps:
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        with:
-          persist-credentials: false
-      # The module test uses `import std;`, which needs CMake's experimental
-      # import-std support. Its opt-in token is CMake-version-specific, so pin
-      # CMake to the version whose token is set in tests/module_cpp20/CMakeLists.txt.
-      - name: Get pinned CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
-        with:
-          cmakeVersion: 4.3.4
-      # Clang: the std library module is provided by libc++ (the image's libstdc++
-      # ships none), and the image's libc++ module manifest has a broken relative
-      # path — repoint it at the real module sources.
-      - name: Use libc++ and fix its module manifest path (Clang)
-        if: matrix.container == 'silkeh/clang:latest'
-        run: |
-          echo "CXXFLAGS=-stdlib=libc++" >> "$GITHUB_ENV"
-          mkdir -p /usr/lib/share && ln -sf /usr/lib/llvm-*/share/libc++ /usr/lib/share/libc++
-      - name: Run CMake
-        run: cmake -S . -B build -DJSON_CI=On
-      - name: Build
-        run: cmake --build build --target ci_module_cpp20
-
  ci_icpc:
+    if: *nightly_set
    runs-on: ubuntu-latest
    # Intel discontinued the classic icc/icpc compiler in oneAPI 2024.0; this is
    # Intel's own last officially published image that still includes it.
@@ -402,6 +574,7 @@ jobs:
        run: cmake --build build --target ci_icpc

  ci_icpx:
+    if: *nightly_set
    runs-on: ubuntu-latest
    container: intel/oneapi-hpckit:latest
    steps:
@@ -416,6 +589,7 @@ jobs:
        run: cmake --build build --target ci_icpx

  ci_nvhpc:
+    if: *nightly_set
    runs-on: ubuntu-latest
    container: nvcr.io/nvidia/nvhpc:25.5-devel-cuda12.9-ubuntu22.04
    steps:
@@ -429,54 +603,10 @@ jobs:
      - name: Build
        run: cmake --build build --target ci_nvhpc

-  ci_emscripten:
-    runs-on: ubuntu-26.04
-    steps:
-      - name: Harden Runner
-        uses: step-security/harden-runner@ccd8616d44fd3846e67624a50d5aad6d37bf2d25 # v2.22.1
-        with:
-          egress-policy: audit
-
-      - name: Install emscripten
-        uses: mymindstorm/setup-emsdk@4528d102f7230f0e7b276855c01ea1159be0e984 # v16
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        with:
-          persist-credentials: false
-      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
-      - name: Run CMake
-        run: cmake -S . -B build -DCMAKE_TOOLCHAIN_FILE=$EMSDK/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake -GNinja
-      - name: Build
-        run: cmake --build build
-
-  ci_test_documentation:
-    runs-on: ubuntu-26.04
-    strategy:
-      matrix:
-        target: [ci_test_examples, ci_test_build_documentation, ci_test_documentation_mermaid]
-    steps:
-      - name: Harden Runner
-        uses: step-security/harden-runner@ccd8616d44fd3846e67624a50d5aad6d37bf2d25 # v2.22.1
-        with:
-          egress-policy: audit
-
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-        with:
-          persist-credentials: false
-          # the git-revision-date-localized plugin needs the history; a shallow clone makes the strict build fail
-          fetch-depth: ${{ matrix.target == 'ci_test_build_documentation' && '0' || '1' }}
-      - uses: actions/setup-node@949feb2413d6458794dcd2491c4babbbce0c15c1 # v7.1.0
-        if: matrix.target == 'ci_test_documentation_mermaid'
-        with:
-          node-version: 24
-      - name: Run CMake
-        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:
+    if: *nightly_set
    runs-on: ubuntu-24.04-arm
    container: gcc:latest
    steps:
@@ -491,3 +621,33 @@ jobs:
        run: cmake -S . -B build -DJSON_CI=On
      - name: Build
        run: cmake --build build --target ci_test_compiler_default
+
+  # A failure of a scheduled run opens an issue, or comments on the open one.
+  nightly_report:
+    needs: [ci_infer, ci_static_analysis_ubuntu_nightly, ci_test_coverage, ci_cuda_example, ci_icpc, ci_icpx, ci_nvhpc, ci_test_arm64]
+    if: ${{ always() && github.event_name == 'schedule' && contains(needs.*.result, 'failure') }}
+    runs-on: ubuntu-26.04
+    permissions:
+      issues: write
+    steps:
+      - name: Harden Runner
+        uses: step-security/harden-runner@ccd8616d44fd3846e67624a50d5aad6d37bf2d25 # v2.22.1
+        with:
+          egress-policy: audit
+
+      - name: Open or update the nightly failure issue
+        env:
+          GH_TOKEN: ${{ github.token }}
+          GH_REPO: ${{ github.repository }}
+          RUN_URL: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
+          WORKFLOW: ${{ github.workflow }}
+          SHA: ${{ github.sha }}
+        run: |
+          title="Nightly CI failure (${WORKFLOW})"
+          body="The nightly run of ${WORKFLOW} on ${SHA:0:10} failed: ${RUN_URL}"
+          number=$(gh issue list --state open --search "in:title \"${title}\"" --json number,title --jq "map(select(.title == \"${title}\")) | .[0].number // empty")
+          if [ -n "$number" ]; then
+            gh issue comment "$number" --body "$body"
+          else
+            gh issue create --title "$title" --body "$body"
+          fi
@@ -7,6 +7,25 @@ on:
      - master
      - release/*
  pull_request:
+    # Skip pull requests that change only files no job here reads. The list is checked by
+    # tools/check_path_filters/check_path_filters.py (repository_checks.yml); change both together.
+    paths:
+      - '**'
+      - '!docs/**'
+      - '!**.md'
+      - '!.github/*'
+      - '!.github/ISSUE_TEMPLATE/**'
+      - '!.github/external_ci/**'
+      - '!.github/workflows/**'
+      - '!.reuse/**'
+      - '!LICENSES/**'
+      - '!CITATION.cff'
+      - '!REUSE.toml'
+      # read by tools/check_build_options in the ci_meson_install job (ubuntu.yml)
+      - 'docs/mkdocs/docs/integration/package_managers.md'
+      # built by the swiftpm job (macos.yml)
+      - 'docs/mkdocs/docs/integration/swift/**'
+      - '.github/workflows/windows.yml'
  workflow_dispatch:

 permissions:
@@ -13,6 +13,72 @@ describe each of them.

 <p class="nj-caption" markdown>The checks grouped by the stage at which they run, from push or pull request through the merge into develop to a release. The badge on each card says whether the check runs on every push or PR, on a schedule, or continuously.</p>

+## How CI runs
+
+Not every job runs for every change. The compiler jobs on Ubuntu are split into three sets, so a pull request gets fast
+feedback and the long jobs run when they matter:
+
+| Set         | When it runs                                                                                                      | What it contains                                                                                                                                                                       |
+|-------------|-------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| PR set      | every push to a pull request, and every push to `develop`, `master`, and `release/*`                              | GCC and Clang with all warnings, Clang-Tidy, sanitizers, IWYU, cpplint, the oldest and newest GCC and Clang, common CMake options, Meson, Emscripten; with the checks that always run, they would have caught at least 92 % of the failing commits of September and October 2026 |
+| full set    | after the PR set passed: on pull requests with the label :rocket: ready to merge, and on every push                | every other compiler, version, C++ standard, and CMake option, the Clang Static Analyzer, Cppcheck, and the C++20 module tests                                                         |
+| nightly set | every night on `develop`, on every push to `master` and `release/*`, and when started by hand                      | Infer, Valgrind, coverage, the Intel and NVIDIA compilers, CUDA, and ARM64; a failure opens an issue                                                                                    |
+
+The jobs on macOS and Windows, the documentation and license checks, and the amalgamation check run on every push and
+pull request. A pull request that changes only the documentation, Markdown files, GitHub metadata, or license files
+skips the compiler workflows (see [`tools/check_path_filters`](https://github.com/nlohmann/json/tree/develop/tools/check_path_filters)).
+
+A maintainer adds the label :rocket: ready to merge when a pull request is ready; the full set then runs, and again on
+every later push to that pull request. A pull request is merged only when the full set passed.
+
+??? abstract "Jobs of the compiler workflows and their sets"
+
+    The table is generated by [`tools/ci_jobs`](https://github.com/nlohmann/json/tree/develop/tools/ci_jobs), which
+    also checks in CI that it is up to date and that every job belongs to exactly one set.
+
+    <!-- ci_jobs: begin -->
+    | Set | Workflow | Job | Configurations |
+    |-----|----------|-----|----------------|
+    | PR set | ubuntu.yml | `ci_test_gcc` | - |
+    | PR set | ubuntu.yml | `ci_meson_install` | - |
+    | PR set | ubuntu.yml | `ci_static_analysis_ubuntu` | ci_cpplint |
+    | PR set | ubuntu.yml | `ci_static_analysis_clang` | ci_test_clang; ci_clang_tidy; ci_test_clang_sanitizer; ci_single_binaries |
+    | PR set | ubuntu.yml | `ci_cmake_options` | ci_test_diagnostics; ci_test_diagnostic_positions; ci_test_noexceptions; ci_test_noglobaludls |
+    | PR set | ubuntu.yml | `ci_test_compilers_gcc_old` | 4.8 |
+    | PR set | ubuntu.yml | `ci_test_compilers_clang` | 3.4 |
+    | PR set | ubuntu.yml | `ci_test_standards_gcc` | 26 |
+    | PR set | ubuntu.yml | `ci_test_standards_clang` | 26, libcxx |
+    | PR set | ubuntu.yml | `ci_emscripten` | - |
+    | full set | ubuntu.yml | `ci_static_analysis_ubuntu_full` | ci_test_single_header; ci_cppcheck; ci_reproducible_tests; ci_non_git_tests; ci_offline_testdata |
+    | full set | ubuntu.yml | `ci_static_analysis_clang_full` | ci_clang_analyze |
+    | full set | ubuntu.yml | `ci_cmake_options_full` | ci_cmake_flags; ci_test_noimplicitconversions; ci_test_legacycomparison; ci_test_disableenumserialization; ci_test_disabletuplereferenceconversion; ci_test_skiplibraryversioncheck; ci_test_simdutf; ci_test_strict_nul_handling; ci_test_delete_deprecated_functions; ci_test_no_thread_local |
+    | full set | ubuntu.yml | `ci_test_compilers_gcc_old_full` | 4.9; 5; 6 |
+    | full set | ubuntu.yml | `ci_test_compilers_gcc_full` | 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; latest |
+    | full set | ubuntu.yml | `ci_test_compilers_clang_full` | 3.5; 3.6; 3.7; 3.8; 3.9; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15-bullseye; 16; 17; 18; 19; 20; 21; 22; latest |
+    | full set | ubuntu.yml | `ci_test_standards_gcc_full` | 11; 14; 17; 20; 23 |
+    | full set | ubuntu.yml | `ci_test_standards_clang_full` | 11, libcxx; 11, libstdcxx; 14, libcxx; 14, libstdcxx; 17, libcxx; 17, libstdcxx; 20, libcxx; 20, libstdcxx; 23, libcxx; 23, libstdcxx; 26, libstdcxx |
+    | full set | ubuntu.yml | `ci_module_cpp20` | gcc:latest; silkeh/clang:latest |
+    | nightly set | ubuntu.yml | `ci_infer` | - |
+    | nightly set | ubuntu.yml | `ci_static_analysis_ubuntu_nightly` | ci_test_valgrind |
+    | nightly set | ubuntu.yml | `ci_test_coverage` | - |
+    | nightly set | ubuntu.yml | `ci_cuda_example` | 11.8.0; 12.1.1; 12.6.3 |
+    | nightly set | ubuntu.yml | `ci_icpc` | - |
+    | nightly set | ubuntu.yml | `ci_icpx` | - |
+    | nightly set | ubuntu.yml | `ci_nvhpc` | - |
+    | nightly set | ubuntu.yml | `ci_test_arm64` | - |
+    | every push and PR | macos.yml | `macos-15` | 16.0; 16.1; 16.2; 16.3; 16.4; 26.0.1; 26.1.1; 26.2; 26.3 |
+    | every push and PR | macos.yml | `macos-26` | 26.4.1; 26.5; 26.6 |
+    | every push and PR | macos.yml | `xcode_standards` | 11; 14; 17; 20; 23; 26 |
+    | every push and PR | macos.yml | `swiftpm` | - |
+    | every push and PR | windows.yml | `mingw` | x64; x86 |
+    | every push and PR | windows.yml | `msvc` | Debug, Win32, default; Debug, Win32, latest; Debug, x64, default; Debug, x64, latest; Release, Win32, default; Release, Win32, latest; Release, x64, default; Release, x64, latest |
+    | every push and PR | windows.yml | `msvc-vs2026` | Debug, Win32, default; Debug, Win32, latest; Debug, x64, default; Debug, x64, latest; Release, Win32, default; Release, Win32, latest; Release, x64, default; Release, x64, latest |
+    | every push and PR | windows.yml | `msvc-arm64` | Debug; Release |
+    | every push and PR | windows.yml | `clang` | 11.0.1; 12.0.1; 13.0.1; 14.0.6; 15.0.7; 16.0.6; 18.1.8; 19.1.7; 20.1.8 |
+    | every push and PR | windows.yml | `clang-cl` | Win32; x64 |
+    | every push and PR | windows.yml | `ci_module_cpp20` | - |
+    <!-- ci_jobs: end -->
+
 ## C++ language compliance and compiler compatibility

 !!! success "Requirement: Compiler support"
@@ -1,26 +1,31 @@
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-<text class="nj-exceptions-line" x="40" y="1594">Dependabot daily, OpenSSF</text>
-<text class="nj-exceptions-line" x="40" y="1612">Scorecard, R&#8203;EUSE</text>
+<rect class="nj-exceptions-box" x="26" y="1516" width="308" height="166" rx="8"/>
+<text class="nj-exceptions-ctitle" x="40" y="1541">Integration, supply chain</text>
+<rect class="nj-exceptions-badge nj-exceptions-badge--push" x="40" y="1552" width="110.5" height="20" rx="10"/>
+<text class="nj-exceptions-badgetext nj-exceptions-badgetext--push" x="95.25" y="1566">every push / PR</text>
+<rect class="nj-exceptions-badge nj-exceptions-badge--sched" x="156.5" y="1552" width="72.7" height="20" rx="10"/>
+<text class="nj-exceptions-badgetext nj-exceptions-badgetext--sched" x="192.85" y="1566">scheduled</text>
+<text class="nj-exceptions-line" x="40" y="1594">CMake 3.5, 3.31.6, and 4.0.0</text>
+<text class="nj-exceptions-line" x="40" y="1612">Meson, Swift Package Manager</text>
+<text class="nj-exceptions-line" x="40" y="1630">dependency review on every PR</text>
+<text class="nj-exceptions-line" x="40" y="1648">Dependabot daily, OpenSSF</text>
+<text class="nj-exceptions-line" x="40" y="1666">Scorecard, R&#8203;EUSE</text>
 </g>
-<line class="nj-exceptions-edge" x1="180" y1="1642" x2="180" y2="1668" marker-end="url(#nj-qa-arrow-n)"/>
-<rect class="nj-exceptions-stage nj-exceptions-stage--merge" x="65" y="1670" width="230" height="34" rx="17"/>
-<text class="nj-exceptions-stagetext" x="180" y="1692">merge into develop</text>
-<line class="nj-exceptions-edge" x1="180" y1="1704" x2="180" y2="1730" marker-end="url(#nj-qa-arrow-n)"/>
-<rect class="nj-exceptions-stage nj-exceptions-stage--merge" x="30" y="1732" width="300" height="46" rx="23"/>
-<text class="nj-exceptions-stagetext" x="180" y="1754">release</text>
-<text class="nj-exceptions-stagesub" x="180" y="1770">no open vulnerability alert</text>
+<line class="nj-exceptions-edge" x1="180" y1="1696" x2="180" y2="1722" marker-end="url(#nj-qa-arrow-n)"/>
+<rect class="nj-exceptions-stage nj-exceptions-stage--merge" x="65" y="1724" width="230" height="34" rx="17"/>
+<text class="nj-exceptions-stagetext" x="180" y="1746">merge into develop</text>
+<line class="nj-exceptions-edge" x1="180" y1="1758" x2="180" y2="1784" marker-end="url(#nj-qa-arrow-n)"/>
+<rect class="nj-exceptions-stage nj-exceptions-stage--merge" x="30" y="1786" width="300" height="46" rx="23"/>
+<text class="nj-exceptions-stagetext" x="180" y="1808">release</text>
+<text class="nj-exceptions-stagesub" x="180" y="1824">no open vulnerability alert</text>
 </svg>
@@ -22,19 +22,24 @@ P = "nj-exceptions-"
 TRIGGERS = {
    "push": ("every push / PR", "push"),
    "pr": ("every PR", "push"),
+    "merge": ("before merge", "push"),
+    "nightly": ("nightly", "sched"),
    "sched": ("scheduled", "sched"),
    "cont": ("continuous", "cont"),
 }

 # title, triggers, lines (at most 31 characters, so they fit a card of the three-column drawing)
 LANES = [
-    ("Build matrix", ["push"], [
+    ("Build matrix", ["push", "merge"], [
        "50+ compilers: GCC, Clang, MSVC,",
        "AppleClang, Intel, NVIDIA, ...",
        "C++11, 14, 17, 20, 23, and 26",
        "libc++ and libstdc++",
        "warnings: Clang -Weverything,",
        "GCC 300+ warnings",
+        "a subset on every push and PR,",
+        "all before merge; Intel, NVIDIA,",
+        "CUDA, and ARM64 nightly",
    ]),
    ("Unit tests (doctest)", ["push"], [
        "every public API function",
@@ -44,7 +49,7 @@ LANES = [
        "custom number, string, array,",
        "and object types",
    ]),
-    ("Coverage", ["push"], [
+    ("Coverage", ["nightly"], [
        "unit tests cover all lines",
        "of the code base",
    ]),
@@ -53,11 +58,11 @@ LANES = [
        "Clang Static Analyzer (52",
        "checkers), IWYU, Codacy",
        "CodeQL, Semgrep, Flawfinder",
-        "(also scheduled)",
+        "(also scheduled); Infer nightly",
    ]),
-    ("Dynamic analysis", ["push"], [
+    ("Dynamic analysis", ["push", "nightly"], [
        "runtime assertions",
-        "Valgrind (Memcheck)",
+        "Valgrind (Memcheck), nightly",
        "address and undefined behavior",
        "sanitizers, integer overflow,",
        "nullability violations",
@@ -178,7 +183,7 @@ def drawing(W, cols, suffix):
    defs = ('<defs><marker id="%s" viewBox="0 0 10 10" refX="9" refY="5" markerWidth="7" markerHeight="7" orient="auto">'
            '<path class="fg-head" d="M0 1 L10 5 L0 9 z"/></marker></defs>' % mid)
    tid, did = "nj-qa-title-" + suffix, "nj-qa-desc-" + suffix
-    desc = ("Every push or pull request starts these checks in parallel: " +
+    desc = ("A push or pull request starts these checks; the badges say when each runs: " +
            "; ".join("%s (%s): %s" % (t, ", ".join(TRIGGERS[k][0] for k in trig), " ".join(lines)) for t, trig, lines in LANES) +
            ". When they pass, the change is merged into develop; a release is made only when no vulnerability alert is open.")
    out = ['<svg class="nj-fig %sqa %sqa--%s" viewBox="0 0 %d %d" role="img" aria-labelledby="%s %s" xmlns="http://www.w3.org/2000/svg">'
@@ -26,7 +26,6 @@
 #include <nlohmann/detail/view/lookup.hpp>
 #include <nlohmann/detail/view/macro_scope.hpp>
 #include <nlohmann/detail/view/node.hpp>
-#include <nlohmann/detail/view/scan.hpp>
 #include <nlohmann/detail/view/view_mode.hpp>

 NLOHMANN_JSON_NAMESPACE_BEGIN
@@ -47,9 +46,10 @@ struct first_true<false, Conditions...> : std::integral_constant < int, 1 + firs
 /// (type_error.316 with the same message), so that an editable document
 /// only holds valid UTF-8: the error is at the first byte that no
 /// well-formed sequence can continue with (Unicode, Table 3-7).
-NLOHMANN_VIEW_ALWAYS_INLINE void check_utf8_bytewise(const unsigned char* p, std::size_t n, std::size_t i)
+inline void check_utf8(const char* s, std::size_t n)
 {
-    for (; i < n;)
+    const auto* const p = reinterpret_cast<const unsigned char*>(s); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
+    for (std::size_t i = 0; i < n;)
    {
        const unsigned char c = p[i];
        if (c < 0x80)
@@ -79,43 +79,6 @@ NLOHMANN_VIEW_ALWAYS_INLINE void check_utf8_bytewise(const unsigned char* p, std
    }
 }

-/// The long-string path of check_utf8(): skips well-formed runs with the
-/// parser's string scan (which stops at a quote, a backslash, or a control
-/// character, all legal here, and at ill-formed UTF-8); the byte-wise check
-/// runs only from where the scan found ill-formed UTF-8, to report it.
-NLOHMANN_VIEW_NOINLINE inline void check_utf8_scan(const unsigned char* p, std::size_t n)
-{
-    const unsigned char* const e = p + n;
-    const unsigned char* q = p;
-    for (;;)
-    {
-        q = scan_string_run<true>(q, e);
-        if (q == e)
-        {
-            return;
-        }
-        if (*q >= 0x80)
-        {
-            check_utf8_bytewise(p, n, static_cast<std::size_t>(q - p));
-            return; // not reached: the scan stopped at ill-formed UTF-8
-        }
-        ++q; // a quote, backslash, or control character
-    }
-}
-
-inline void check_utf8(const char* s, std::size_t n)
-{
-    const auto* const p = reinterpret_cast<const unsigned char*>(s); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
-    if (NLOHMANN_VIEW_UNLIKELY(n >= 32))
-    {
-        check_utf8_scan(p, n);
-        return;
-    }
-    // short strings: the vector scan costs more than it saves; (the loop is
-    // inlined with a constant start, so this path is the plain byte-wise check)
-    check_utf8_bytewise(p, n, 0);
-}
-
 /*!
@brief the edits of an editable basic_json_document

@@ -3740,8 +3740,6 @@ NLOHMANN_JSON_NAMESPACE_END

 // #include <nlohmann/detail/view/node.hpp>

-// #include <nlohmann/detail/view/scan.hpp>
-
 // #include <nlohmann/detail/view/view_mode.hpp>
 //     __ _____ _____ _____
 //  __|  |   __|     |   | |  JSON for Modern C++
@@ -3815,9 +3813,10 @@ struct first_true<false, Conditions...> : std::integral_constant < int, 1 + firs
 /// (type_error.316 with the same message), so that an editable document
 /// only holds valid UTF-8: the error is at the first byte that no
 /// well-formed sequence can continue with (Unicode, Table 3-7).
-NLOHMANN_VIEW_ALWAYS_INLINE void check_utf8_bytewise(const unsigned char* p, std::size_t n, std::size_t i)
+inline void check_utf8(const char* s, std::size_t n)
 {
-    for (; i < n;)
+    const auto* const p = reinterpret_cast<const unsigned char*>(s); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
+    for (std::size_t i = 0; i < n;)
    {
        const unsigned char c = p[i];
        if (c < 0x80)
@@ -3847,43 +3846,6 @@ NLOHMANN_VIEW_ALWAYS_INLINE void check_utf8_bytewise(const unsigned char* p, std
    }
 }

-/// The long-string path of check_utf8(): skips well-formed runs with the
-/// parser's string scan (which stops at a quote, a backslash, or a control
-/// character, all legal here, and at ill-formed UTF-8); the byte-wise check
-/// runs only from where the scan found ill-formed UTF-8, to report it.
-NLOHMANN_VIEW_NOINLINE inline void check_utf8_scan(const unsigned char* p, std::size_t n)
-{
-    const unsigned char* const e = p + n;
-    const unsigned char* q = p;
-    for (;;)
-    {
-        q = scan_string_run<true>(q, e);
-        if (q == e)
-        {
-            return;
-        }
-        if (*q >= 0x80)
-        {
-            check_utf8_bytewise(p, n, static_cast<std::size_t>(q - p));
-            return; // not reached: the scan stopped at ill-formed UTF-8
-        }
-        ++q; // a quote, backslash, or control character
-    }
-}
-
-inline void check_utf8(const char* s, std::size_t n)
-{
-    const auto* const p = reinterpret_cast<const unsigned char*>(s); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
-    if (NLOHMANN_VIEW_UNLIKELY(n >= 32))
-    {
-        check_utf8_scan(p, n);
-        return;
-    }
-    // short strings: the vector scan costs more than it saves; (the loop is
-    // inlined with a constant start, so this path is the plain byte-wise check)
-    check_utf8_bytewise(p, n, 0);
-}
-
 /*!
@brief the edits of an editable basic_json_document

@@ -941,123 +941,3 @@ TEST_CASE("json_view edits: duplicate keys")
        CHECK(d.root()["o"]["d"].get<int>() == 0);
    }
 }
-
-#if !defined(JSON_NOEXCEPTION)
-TEST_CASE("json_view edits: check_utf8 agrees with the byte-wise check")
-{
-    namespace dv = nlohmann::detail::view;
-
-    // "ok" or the exception message
-    const auto run = [](bool fast, const std::string & s) -> std::string
-    {
-        try
-        {
-            if (fast)
-            {
-                dv::check_utf8(s.data(), s.size());
-            }
-            else
-            {
-                dv::check_utf8_bytewise(reinterpret_cast<const unsigned char*>(s.data()), s.size(), 0);
-            }
-        }
-        catch (const json::type_error& e)
-        {
-            return {e.what()};
-        }
-        return {"ok"};
-    };
-    std::size_t errors = 0;
-    const auto same = [&](const std::string & s)
-    {
-        const std::string a = run(true, s);
-        const std::string b = run(false, s);
-        if (a != b)
-        {
-            INFO("fast: " << a << ", byte-wise: " << b << ", length " << s.size());
-            CHECK(a == b);
-        }
-        errors += b != "ok" ? 1u : 0u;
-    };
-
-    const std::vector<std::string> pieces =
-    {
-        "a", "Z", " ", "\"", "\\", "\n", "\x01", "\x7f", "\xc3\xa4", "\xe4\xb8\xad", "\xf0\x9f\x98\x80",
-        "\x80", "\xbf", "\xc0\x80", "\xc1\xbf", "\xc2", "\xe0\x80\x80", "\xe0\x9f\xbf", "\xed\xa0\x80", "\xed\xbf\xbf",
-        "\xf0\x80\x80\x80", "\xf0\x8f\xbf\xbf", "\xf4\x90\x80\x80", "\xf4\x8f\xbf\xbf", "\xf5", "\xf8", "\xff", "\xfe",
-        "\xe4\xb8", "\xf0\x9f\x98", "\xf0\x9f", "\xf0"
-    };
-
-    // every piece behind prefixes of every length, and followed by more bytes
-    for (std::size_t prefix = 0; prefix <= 64; ++prefix)
-    {
-        for (const auto& piece : pieces)
-        {
-            same(std::string(prefix, 'x') + piece);
-            same(std::string(prefix, 'x') + piece + "yz");
-            same(std::string(prefix, '"') + piece);
-            same(std::string(prefix, '\xc3') + piece);
-            same(std::string(prefix / 2, '\xc3').append(prefix / 2, '\xa4') + piece);
-            same(std::string(prefix, 'x') + "\xe4\xb8\xad" + piece);
-        }
-    }
-    // an invalid byte at every position of valid strings of every length
-    for (std::size_t len = 0; len <= 64; ++len)
-    {
-        const std::string ascii(len, 'a');
-        std::string mixed;
-        while (mixed.size() < len)
-        {
-            if (mixed.size() % 7 == 0)
-            {
-                mixed += "\xc3\xa4";
-            }
-            else if (mixed.size() % 11 == 0)
-            {
-                mixed += "\xf0\x9f\x98\x80";
-            }
-            else
-            {
-                mixed += "a";
-            }
-        }
-        same(ascii);
-        same(mixed);
-        for (std::size_t pos = 0; pos < len; ++pos)
-        {
-            for (const char bad :
-                    {'\x80', '\xc0', '\xc2', '\xe0', '\xf4', '\xff', '"', '\\', '\x1f'
-                    })
-            {
-                std::string s = ascii;
-                s[pos] = bad;
-                same(s);
-                s = mixed;
-                s[pos] = bad;
-                same(s);
-            }
-        }
-    }
-    // random bytes, biased to the interesting ones
-    std::mt19937 gen(5869); // NOLINT(cert-msc32-c,cert-msc51-cpp,bugprone-random-generator-seed): reproducible
-    static const std::array<unsigned char, 23> interesting = {{0x00, 0x1f, 0x22, 0x5c, 0x7f, 0x80, 0x8f, 0x90, 0x9f, 0xa0, 0xbf, 0xc0, 0xc2, 0xdf, 0xe0, 0xe1, 0xed, 0xef, 0xf0, 0xf1, 0xf4, 0xf5, 0xff}};
-    for (int i = 0; i < 100000; ++i)
-    {
-        std::string s(gen() % 80, 'a');
-        for (auto& c : s)
-        {
-            const unsigned r = gen() % 8;
-            if (r == 0)
-            {
-                c = static_cast<char>(gen() & 0xff);
-            }
-            else if (r == 1)
-            {
-                c = static_cast<char>(interesting[gen() % interesting.size()]);
-            }
-        }
-        same(s);
-    }
-    CHECK(errors > 1000);
-}
-#endif
@@ -0,0 +1,34 @@
+# check_path_filters
+
+The compiler workflows [`ubuntu.yml`](../../.github/workflows/ubuntu.yml),
+[`macos.yml`](../../.github/workflows/macos.yml), and [`windows.yml`](../../.github/workflows/windows.yml) skip pull
+requests that change only files no compiler job reads: the documentation, Markdown files, GitHub metadata, other
+workflows, and the license files. Pushes to `develop`, `master`, and `release/*` always run them. The documentation,
+license, and path-filter checks run in [`repository_checks.yml`](../../.github/workflows/repository_checks.yml), which
+has no path filter.
+
+The filter starts with `'**'` and excludes these files explicitly, so a new file runs the compiler workflows unless it
+is excluded on purpose. [`check_path_filters.py`](check_path_filters.py) holds the filter (`PATHS`) and checks that
+
+- each of the three workflows has exactly this filter, with its own workflow file included,
+- the CI targets that read excluded files (`UNFILTERED_TARGETS`) do not run in these workflows, and
+- no file the filter keeps (sources, tests, build files, tools, workflows) mentions an excluded file or directory
+  outside a comment line, unless the mention is listed in `KNOWN_REFERENCES` with a reason.
+
+When the check reports a mention, decide whether a compiler job reads that file:
+
+- If it does, include the file in `PATHS` after the exclusions (as `package_managers.md` and the Swift example are) and
+  copy the new filter into the three workflows.
+- If it does not, add the mention to `KNOWN_REFERENCES` with the reason.
+
+Run the check with
+
+```shell
+python3 tools/check_path_filters/check_path_filters.py
+```
+
+To see which workflows a pull request would run, pass the changed files:
+
+```shell
+python3 tools/check_path_filters/check_path_filters.py --changed $(git diff --name-only origin/develop)
+```
@@ -0,0 +1,273 @@
+#!/usr/bin/env python3
+"""Check the path filters of the compiler workflows.
+
+ubuntu.yml, macos.yml and windows.yml skip pull requests that change only files
+no compiler job reads (documentation, Markdown files, GitHub metadata, license
+files). The filter starts with '**' and excludes these files explicitly, so a
+new file runs the workflows unless it is excluded on purpose.
+
+The script checks that
+
+- each of the three workflows has exactly the filter defined in PATHS below,
+  with its own workflow file included, and
+- no tracked file that the filter keeps (sources, tests, build files, tools,
+  workflows) mentions a file the filter excludes, unless the mention is listed
+  in KNOWN_REFERENCES with the reason why it does not matter.
+
+A mention found this way must either be added to PATHS as an included path
+(the file is read by a compiler job) or to KNOWN_REFERENCES (it is not).
+
+With --changed FILE..., the script prints instead which workflows a pull
+request changing these files would run.
+"""
+
+import argparse
+import os
+import re
+import subprocess  # nosec B404
+import sys
+
+REPO_ROOT = os.path.normpath(os.path.join(sys.path[0], '..', '..'))
+SELF = 'tools/check_path_filters/check_path_filters.py'
+
+WORKFLOWS = ['.github/workflows/ubuntu.yml', '.github/workflows/macos.yml', '.github/workflows/windows.yml']
+
+# The pull_request paths filter of the workflows above; '{workflow}' is replaced
+# with the workflow's own file. GitHub applies the patterns in order: a file
+# matching a later pattern is included ('pattern') or excluded ('!pattern').
+PATHS = [
+    '**',
+    '!docs/**',
+    '!**.md',
+    '!.github/*',
+    '!.github/ISSUE_TEMPLATE/**',
+    '!.github/external_ci/**',
+    '!.github/workflows/**',
+    '!.reuse/**',
+    '!LICENSES/**',
+    '!CITATION.cff',
+    '!REUSE.toml',
+    # read by tools/check_build_options in the ci_meson_install job (ubuntu.yml)
+    'docs/mkdocs/docs/integration/package_managers.md',
+    # built by the swiftpm job (macos.yml)
+    'docs/mkdocs/docs/integration/swift/**',
+    '{workflow}',
+]
+
+# Mentions of excluded files that no job of the three workflows depends on:
+# (file that mentions it, the mention, reason)
+KNOWN_REFERENCES = [
+    ('cmake/ci.cmake', 'docs/', 'ci_test_examples; runs in repository_checks.yml, which has no path filter'),
+    ('cmake/ci.cmake', 'docs/mkdocs/', 'ci_test_build_documentation and ci_test_documentation_mermaid; they run in '
+                                       'repository_checks.yml, which has no path filter'),
+    ('cmake/ci.cmake', 'docs/mkdocs/docs/examples/', 'indentation check of ci_test_amalgamation; the same check runs in '
+                                                     'check_amalgamation.yml, which has no path filter'),
+    ('Makefile', 'docs/mkdocs/docs/examples/', 'make pretty; runs in check_amalgamation.yml, which has no path filter'),
+    ('Makefile', 'ChangeLog.md', 'make ChangeLog.md writes the file; no CI job runs it'),
+    ('Makefile', 'tests/fuzzing.md', 'help text'),
+    ('Makefile', 'tools/generate_natvis/README.md', 'help text'),
+    ('tests/src/make_test_data_available.hpp', 'README.md', 'a file of the external test data repository'),
+    ('tools/check_build_options/check_build_options.py', 'docs/', 'builds the path of package_managers.md, which '
+                                                                  'PATHS includes'),
+    ('tools/ci_jobs/ci_jobs.py', 'docs/mkdocs/docs/community/quality_assurance.md',
+     'checks the job table; runs in repository_checks.yml, which has no path filter'),
+    ('tools/ci_jobs/ci_jobs.py', '.github/workflows/repository_checks.yml', 'read by --compare, a manual check'),
+    ('tools/ci_jobs/ci_jobs.py', '.github/workflows/check_amalgamation.yml', 'read by --compare, a manual check'),
+]
+
+
+# CI targets that read excluded files; they must run in a workflow without a path filter
+UNFILTERED_TARGETS = ['ci_test_examples', 'ci_test_build_documentation', 'ci_test_documentation_mermaid',
+                      'ci_test_amalgamation', 'ci_reuse_compliance']
+
+
+def git_files(root):
+    # fixed command, no user input; includes new files not yet added, so a local run
+    # sees what CI sees after the commit
+    out = subprocess.check_output(['git', 'ls-files', '-z', '--cached', '--others', '--exclude-standard'], cwd=root)  # nosec B603, B607
+    return [f for f in out.decode('utf-8').split('\0') if f]
+
+
+def glob_to_regex(pattern):
+    """Translate a GitHub Actions path pattern to a regular expression."""
+    regex = ''
+    i = 0
+    while i < len(pattern):
+        if pattern.startswith('**', i):
+            regex += '.*'
+            i += 2
+        elif pattern[i] == '*':
+            regex += '[^/]*'
+            i += 1
+        elif pattern[i] == '?':
+            regex += '[^/]'
+            i += 1
+        else:
+            regex += re.escape(pattern[i])
+            i += 1
+    return re.compile(regex + r'\Z')
+
+
+def compile_filter(paths, workflow):
+    return [(p.startswith('!'), glob_to_regex(p.lstrip('!').replace('{workflow}', workflow))) for p in paths]
+
+
+def included(compiled, path):
+    result = False
+    for negated, regex in compiled:
+        if regex.match(path):
+            result = not negated
+    return result
+
+
+def read_filter(root, workflow):
+    """Return the pull_request paths list of a workflow file."""
+    with open(os.path.join(root, workflow), encoding='utf-8') as f:
+        lines = f.read().splitlines()
+    paths = None
+    in_pull_request = False
+    for line in lines:
+        if re.match(r'^  pull_request:', line):
+            in_pull_request = True
+            continue
+        if in_pull_request:
+            if re.match(r'^  \S', line) or re.match(r'^\S', line):
+                break
+            if re.match(r'^    paths:\s*$', line):
+                paths = []
+                continue
+            m = re.match(r"^      - '(.*)'\s*(#.*)?$", line)
+            if paths is not None and m:
+                paths.append(m.group(1))
+            elif paths is not None and line.strip() and not line.strip().startswith('#'):
+                break
+    return paths
+
+
+TOKEN = re.compile(r'(["\'/]?)([\w.-]+(?:/[\w.-]+)*)')
+
+
+COMMENT_LINE = re.compile(r'^[ \t]*(//|#|/?\*|--).*$', re.MULTILINE)
+
+
+class Mentions:
+    """Finds the words and paths in a text that name an excluded file or directory."""
+
+    def __init__(self, files, excluded, is_excluded):
+        self.files = set(files)
+        self.excluded = excluded
+        self.dirs = {'/'.join(f.split('/')[:n]) for f in files for n in range(1, f.count('/') + 1)}
+        # an excluded directory: a new file in it would be excluded
+        self.excluded_dirs = {d for d in self.dirs if is_excluded(d + '/new_file')}
+        # base names that only excluded files have, e.g. 'ChangeLog.md' but not 'CMakeLists.txt'
+        self.names = {os.path.basename(f) for f in excluded} - {os.path.basename(f) for f in files if f not in excluded}
+
+    def find(self, text):
+        """Yield (offset, mention) for every word or path in text that names an excluded file or directory."""
+        for m in TOKEN.finditer(text):
+            parts = m.group(2).rstrip('/').split('/')
+            # a single word names a directory only in a path context, e.g. 'docs' in os.path.join('docs', ...)
+            path_context = len(parts) > 1 or m.group(1)
+            for i in range(len(parts)):
+                path = '/'.join(parts[i:])
+                if path in self.files:
+                    if path in self.excluded:
+                        yield m.start(2), path
+                    break
+                if path in self.dirs and path_context:
+                    if path in self.excluded_dirs:
+                        yield m.start(2), path + '/'
+                    break
+            else:
+                if parts[-1] in self.names and '.' in parts[-1]:
+                    yield m.start(2), parts[-1]
+
+
+def known(path, mention):
+    return any(path == file and mention == known_mention for file, known_mention, _ in KNOWN_REFERENCES)
+
+
+def check_workflows(root):
+    """Return the errors in the filters of the workflows and in the targets they run."""
+    errors = []
+    for workflow in WORKFLOWS:
+        expected = [p.replace('{workflow}', workflow) for p in PATHS]
+        actual = read_filter(root, workflow)
+        if actual != expected:
+            errors.append('{}: the pull_request paths filter differs from tools/check_path_filters/check_path_filters.py\n'
+                          '  expected: {}\n  actual:   {}'.format(workflow, expected, actual))
+        with open(os.path.join(root, workflow), encoding='utf-8') as f:
+            text = f.read()
+        errors += ['{}: runs {}, which reads excluded files; run it in repository_checks.yml'.format(workflow, target)
+                   for target in UNFILTERED_TARGETS if re.search(r'\b' + target + r'\b', text)]
+    return errors
+
+
+def scanned_text(root, path):
+    """Return the text of a kept file without comment lines and without the filter itself, or None to skip it."""
+    # third-party code and Markdown files read nothing; this script lists the excluded files
+    if path.startswith('tests/thirdparty/') or path.endswith('.md') or path == SELF:
+        return None
+    try:
+        with open(os.path.join(root, path), encoding='utf-8') as f:
+            # a mention in a comment line reads nothing; keep the line numbers
+            text = COMMENT_LINE.sub('', f.read())
+    except (UnicodeDecodeError, OSError):
+        return None
+    if path in WORKFLOWS:
+        # the filter itself lists the excluded files
+        for p in PATHS:
+            text = text.replace("      - '{}'".format(p.replace('{workflow}', path)), '')
+    return text
+
+
+def check_mentions(root, files, excluded, finder):
+    """Return an error for every mention of an excluded file in a kept file that KNOWN_REFERENCES does not list."""
+    errors = []
+    for path in sorted(set(files) - excluded):
+        text = scanned_text(root, path)
+        reported = set()
+        for offset, mention in finder.find(text or ''):
+            if mention not in reported and not known(path, mention):
+                reported.add(mention)
+                line = text.count('\n', 0, offset) + 1
+                errors.append('{}:{}: mentions excluded {}; include it in PATHS if a compiler job reads it, '
+                              'or add it to KNOWN_REFERENCES'.format(path, line, mention))
+    return errors
+
+
+def check(root):
+    files = git_files(root)
+    union = [compile_filter(PATHS, w) for w in WORKFLOWS]
+
+    def is_excluded(path):
+        return not any(included(c, path) for c in union)
+
+    excluded = {f for f in files if is_excluded(f)}
+    errors = check_workflows(root) + check_mentions(root, files, excluded, Mentions(files, excluded, is_excluded))
+    for e in errors:
+        print(e)
+    if not errors:
+        print('path filters OK: {} of {} tracked files skip the compiler workflows'.format(len(excluded), len(files)))
+    return 1 if errors else 0
+
+
+def explain(changed):
+    for workflow in WORKFLOWS:
+        compiled = compile_filter(PATHS, workflow)
+        hits = [f for f in changed if included(compiled, f)]
+        print('{}: {}'.format(workflow, 'runs ({})'.format(', '.join(hits[:3]) + (' ...' if len(hits) > 3 else ''))
+                                       if hits else 'skipped'))
+    return 0
+
+
+def main():
+    parser = argparse.ArgumentParser(description=__doc__.splitlines()[0])
+    parser.add_argument('--root', default=REPO_ROOT, help='repository root')
+    parser.add_argument('--changed', nargs='+', metavar='FILE', help='show which workflows these changed files run')
+    args = parser.parse_args()
+    return explain(args.changed) if args.changed else check(args.root)
+
+
+if __name__ == '__main__':
+    sys.exit(main())
@@ -0,0 +1,27 @@
+# ci_jobs
+
+The compiler jobs of [`ubuntu.yml`](../../.github/workflows/ubuntu.yml) are split into three sets, chosen by each job's
+`if:` condition (see [How CI runs](https://json.nlohmann.me/community/quality_assurance/#how-ci-runs)):
+
+- **PR set**: every push to a pull request, and every push to `develop`, `master`, and `release/*`;
+- **full set**: after the PR set passed, on pull requests with the label "🚀 ready to merge" and on every push;
+- **nightly set**: every night on `develop`, on every push to `master` and `release/*`, and when started by hand.
+
+A matrix whose entries belong to different sets is split into one job per set: the full-set job gets the suffix
+`_full`, the nightly-set job `_nightly`, and both share their steps with the PR-set job through YAML anchors.
+
+[`ci_jobs.py`](ci_jobs.py) checks that
+
+- every job of `ubuntu.yml` has the `if:` condition of exactly one set (the conditions are in `SETS`),
+- every full-set job waits for (`needs:`) exactly the PR set, and `nightly_report` for exactly the nightly set, and
+- the job table in [`quality_assurance.md`](../../docs/mkdocs/docs/community/quality_assurance.md) is up to date.
+
+```shell
+python3 -m venv venv && venv/bin/pip install -r tools/ci_jobs/requirements.txt
+venv/bin/python tools/ci_jobs/ci_jobs.py                       # check
+venv/bin/python tools/ci_jobs/ci_jobs.py --markdown            # print the job table for the documentation
+venv/bin/python tools/ci_jobs/ci_jobs.py --compare origin/develop  # list configurations added or removed since develop
+```
+
+Use `--compare` when changing the workflows: a configuration that disappears fails it, so no compiler, version, or
+standard is dropped by accident when jobs are split, merged, or moved between sets.
@@ -0,0 +1,230 @@
+#!/usr/bin/env python3
+"""List and check the jobs of the compiler workflows and the set each job belongs to.
+
+The jobs of a tiered workflow (ubuntu.yml) belong to one of three sets, chosen
+by the job's `if:` condition:
+
+- PR set: every pull request push and every push,
+- full set: after the PR set passed, on pushes and on pull requests with the
+  "🚀 ready to merge" label,
+- nightly set: nightly on develop, on pushes to master and release/*, and when
+  started by hand.
+
+The jobs of the other workflows run on every push and pull request.
+
+The script checks that every job of a tiered workflow belongs to exactly one
+set, that the full set waits for the whole PR set, that the nightly report
+waits for the whole nightly set, and that the job table in
+docs/mkdocs/docs/community/quality_assurance.md is up to date.
+
+  --markdown       print the job table for the documentation
+  --compare REF    list the configurations (job and matrix values) added or
+                   removed since the git revision REF; fails if one was removed
+"""
+
+import argparse
+import collections
+import itertools
+import os
+import re
+import subprocess  # nosec B404
+import sys
+
+import yaml
+
+REPO_ROOT = os.path.normpath(os.path.join(sys.path[0], '..', '..'))
+DOCS = 'docs/mkdocs/docs/community/quality_assurance.md'
+BEGIN, END = '<!-- ci_jobs: begin -->', '<!-- ci_jobs: end -->'
+
+WORKFLOWS = ['.github/workflows/ubuntu.yml', '.github/workflows/macos.yml', '.github/workflows/windows.yml']
+TIERED = ['.github/workflows/ubuntu.yml']
+# --compare also counts the jobs of these workflows, so a job moved between workflows is not a removed one
+COMPARED = WORKFLOWS + ['.github/workflows/repository_checks.yml', '.github/workflows/check_amalgamation.yml']
+
+LABEL = '🚀 ready to merge'
+SETS = collections.OrderedDict([
+    ('PR set', "${{ github.event_name != 'schedule' && (github.event.action != 'labeled' || "
+               "github.event.label.name == '" + LABEL + "') }}"),
+    ('full set', "${{ github.event_name == 'push' || github.event_name == 'workflow_dispatch' || "
+                 "contains(github.event.pull_request.labels.*.name, '" + LABEL + "') }}"),
+    ('nightly set', "${{ github.event_name == 'schedule' || github.event_name == 'workflow_dispatch' || "
+                    "(github.event_name == 'push' && github.ref != 'refs/heads/develop') }}"),
+])
+UNTIERED = 'every push and PR'
+REPORT_JOB = 'nightly_report'
+
+# a job split by set keeps its name and gets one of these suffixes
+SUFFIXES = {'full set': '_full', 'nightly set': '_nightly'}
+
+
+def read(root, path, ref=None):
+    if ref is None:
+        with open(os.path.join(root, path), encoding='utf-8') as f:
+            return f.read()
+    # fixed command; ref is a git revision given on the command line
+    return subprocess.check_output(['git', 'show', '{}:{}'.format(ref, path)], cwd=root,  # nosec B603, B607
+                                   stderr=subprocess.DEVNULL).decode('utf-8')
+
+
+def add_include(combos, keys, inc):
+    """Apply one include entry: extend the matching configurations, or add it as a new one."""
+    matching = [c for c in combos if all(c[k] == v for k, v in inc.items() if k in keys)]
+    for c in matching:
+        c.update({k: v for k, v in inc.items() if k not in keys})
+    if not matching:
+        combos.append(dict(inc))
+
+
+def expand(matrix):
+    """Return the configurations of a job's strategy.matrix like GitHub Actions does."""
+    if not matrix:
+        return [{}]
+    keys = [k for k in matrix if k not in ('include', 'exclude')]
+    combos = [dict(zip(keys, values)) for values in itertools.product(*(matrix[k] for k in keys))] if keys else []
+    for ex in matrix.get('exclude') or []:
+        combos = [c for c in combos if any(c.get(k) != v for k, v in ex.items())]
+    for inc in matrix.get('include') or []:
+        add_include(combos, keys, inc)
+    return combos
+
+
+def jobs_of(root, workflow, ref=None):
+    """Yield (job id, set, list of configurations) for every job of a workflow."""
+    data = yaml.safe_load(read(root, workflow, ref))
+    for job_id, job in data['jobs'].items():
+        condition = job.get('if')
+        job_set = UNTIERED if condition is None else next((s for s, c in SETS.items() if c == condition), None)
+        matrix = (job.get('strategy') or {}).get('matrix')
+        yield job_id, job_set, job, expand(matrix)
+
+
+def base_id(job_id, job_set):
+    suffix = SUFFIXES.get(job_set)
+    return job_id[:-len(suffix)] if suffix and job_id.endswith(suffix) else job_id
+
+
+def label(config):
+    return ', '.join(str(v) for k, v in config.items() if k != 'os' or len(config) == 1)
+
+
+def configurations(root, ref=None):
+    """Return a Counter of (job name without set suffix, configuration) over the compared workflows."""
+    result = collections.Counter()
+    for workflow in COMPARED:
+        try:
+            jobs = list(jobs_of(root, workflow, ref))
+        except (OSError, subprocess.CalledProcessError):
+            continue  # the workflow does not exist in this revision
+        for job_id, job_set, _, configs in jobs:
+            if job_id == REPORT_JOB:
+                continue
+            for c in configs:
+                result[(base_id(job_id, job_set), tuple(sorted((k, str(v)) for k, v in c.items())))] += 1
+    return result
+
+
+def markdown(root):
+    rows = []
+    order = list(SETS) + [UNTIERED]
+    for workflow in WORKFLOWS:
+        for job_id, job_set, _, configs in jobs_of(root, workflow):
+            if job_id == REPORT_JOB:
+                continue
+            labels = [label(c) for c in configs if c]
+            rows.append((order.index(job_set) if job_set in order else len(order), os.path.basename(workflow), job_id,
+                         job_set or 'no set', '; '.join(labels) or '-'))
+    rows.sort(key=lambda r: (r[0], r[1]))
+    lines = ['| Set | Workflow | Job | Configurations |', '|-----|----------|-----|----------------|']
+    lines += ['| {} | {} | `{}` | {} |'.format(s, w, j, c) for _, w, j, s, c in rows]
+    return lines
+
+
+def check_sets(workflow, jobs):
+    """Return the errors in the sets of a tiered workflow's jobs and the jobs of each set."""
+    errors = []
+    by_set = collections.defaultdict(set)
+    for job_id, job_set, _, _ in jobs:
+        if job_id == REPORT_JOB:
+            continue
+        if job_set in SETS:
+            by_set[job_set].add(job_id)
+        else:
+            errors.append('{}: job {} has an if: condition of no set; use one of the conditions in '
+                          'tools/ci_jobs/ci_jobs.py'.format(workflow, job_id))
+    return errors, by_set
+
+
+def check_needs(workflow, jobs, by_set):
+    """Return the errors in the needs: of a tiered workflow's jobs."""
+    required = {'full set': by_set['PR set'], 'PR set': set(), 'nightly set': set()}
+    errors = []
+    for job_id, job_set, job, _ in jobs:
+        needs = job.get('needs') or []
+        needs = {needs} if isinstance(needs, str) else set(needs)
+        expected = by_set['nightly set'] if job_id == REPORT_JOB else required.get(job_set, needs)
+        if needs != expected:
+            errors.append('{}: job {} must need exactly: {}'.format(workflow, job_id, ', '.join(sorted(expected)) or 'no job'))
+    return errors
+
+
+def check_docs(root):
+    """Return an error if the job table in the documentation is not up to date."""
+    text = read(root, DOCS)
+    block = re.search(re.escape(BEGIN) + r'\n(.*?)\n[ \t]*' + re.escape(END), text, re.S)
+    if not block:
+        return ['{}: markers {} and {} not found'.format(DOCS, BEGIN, END)]
+    indent = re.match(r'[ \t]*', block.group(1)).group(0)
+    if block.group(1) != '\n'.join(indent + line for line in markdown(root)):
+        return ['{}: the job table is out of date; replace it with the output of '
+                'python3 tools/ci_jobs/ci_jobs.py --markdown'.format(DOCS)]
+    return []
+
+
+def check(root):
+    errors = []
+    for workflow in TIERED:
+        jobs = list(jobs_of(root, workflow))
+        set_errors, by_set = check_sets(workflow, jobs)
+        errors += set_errors + check_needs(workflow, jobs, by_set)
+    errors += check_docs(root)
+
+    for e in errors:
+        print(e)
+    if not errors:
+        counts = collections.Counter()
+        for workflow in WORKFLOWS:
+            for job_id, job_set, _, configs in jobs_of(root, workflow):
+                if job_id != REPORT_JOB:
+                    counts[job_set] += len(configs)
+        print('CI jobs OK: ' + ', '.join('{} {}'.format(n, s) for s, n in counts.items()))
+    return 1 if errors else 0
+
+
+def compare(root, ref):
+    before, after = configurations(root, ref), configurations(root)
+    removed, added = before - after, after - before
+    for title, diff in (('removed', removed), ('added', added)):
+        for job, config in sorted(diff.elements()):
+            print('{}: {} ({})'.format(title, job, ', '.join('{}={}'.format(k, v) for k, v in config)))
+    print('{} configurations before, {} after; {} removed, {} added'.format(
+        sum(before.values()), sum(after.values()), sum(removed.values()), sum(added.values())))
+    return 1 if removed else 0
+
+
+def main():
+    parser = argparse.ArgumentParser(description=__doc__.splitlines()[0])
+    parser.add_argument('--root', default=REPO_ROOT, help='repository root')
+    group = parser.add_mutually_exclusive_group()
+    group.add_argument('--markdown', action='store_true', help='print the job table for the documentation')
+    group.add_argument('--compare', metavar='REF', help='list the configurations added or removed since REF')
+    args = parser.parse_args()
+    if args.markdown:
+        print('\n'.join(markdown(args.root)))
+        return 0
+    if args.compare:
+        return compare(args.root, args.compare)
+    return check(args.root)
+
+
+if __name__ == '__main__':
+    sys.exit(main())
@@ -0,0 +1 @@
+PyYAML==6.0.3
Author	SHA1	Message	Date
Niels Lohmann	d587214ab2	Merge ci/path-filters Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-28 07:11:44 +01:00
Niels Lohmann	bd442d5d07	Merge develop Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-28 07:11:43 +01:00
Niels Lohmann	087df7b0c2	Split the Ubuntu jobs into a PR set, a full set, and a nightly set All ~100 Ubuntu jobs ran on every push to every pull request. They now belong to three sets, chosen by each job's if: condition: - PR set (16 configurations): every push to a pull request and every push. Together with the checks that always run, these jobs would have caught at least 92 % of the failing commits of Sep/Oct 2026. - full set (73 configurations): after the PR set passed, on pushes and on pull requests with the "🚀 ready to merge" label. - nightly set (10 configurations): Infer, Valgrind, coverage, icpc, icpx, nvhpc, CUDA, and ARM64; nightly on develop, on pushes to master and release/*, and by hand. A failed nightly run opens or updates an issue. A matrix whose entries belong to different sets is split into one job per set; the jobs share their steps through YAML anchors. No configuration is removed: tools/ci_jobs/ci_jobs.py --compare lists 150 configurations before and after. The same tool checks in CI that every job belongs to exactly one set, that the full set waits for the whole PR set, and that the job table in quality_assurance.md is up to date. The documentation describes the sets in a new section "How CI runs", and the QA pipeline figure shows the new badges. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-27 19:40:21 +01:00
Niels Lohmann	eae3c8217b	Split the checks of check_path_filters.py into smaller functions Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-27 19:39:20 +01:00
Niels Lohmann	960c234cc6	Do not report the excluded files that check_path_filters.py lists itself Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-27 18:58:36 +01:00
Niels Lohmann	b6e24d19a9	Skip the compiler workflows for pull requests that change no build input ubuntu.yml, macos.yml and windows.yml run about 155 jobs on every pull request, including those that change only the documentation. They now have a pull_request path filter: it starts with '*' and excludes the documentation, Markdown files, GitHub metadata, other workflows and the license files, so a new file runs them unless it is excluded on purpose. Pushes to develop, master and release/ are not filtered. The documentation jobs and the REUSE check move from ubuntu.yml to the new repository_checks.yml, which has no path filter and also runs tools/check_path_filters. That check keeps the three filters identical and fails when a file the compiler jobs keep mentions an excluded file. It found two: tools/check_build_options reads the Meson section of package_managers.md, and the swiftpm job builds the Swift example from the documentation; both are included in the filter. Signed-off-by: Niels Lohmann <mail@nlohmann.me>	2026-10-27 18:35:03 +01:00