Merge branch 'master' into stable

.clang-tidy

@@ -1,8 +1,11 @@
 FormatStyle: file
 
 Checks: '
+*bugprone*,
 cppcoreguidelines-init-variables,
+cppcoreguidelines-slicing,
 clang-analyzer-optin.cplusplus.VirtualCall,
+google-explicit-constructor,
 llvm-namespace-comment,
 misc-misplaced-const,
 misc-non-copyable-objects,
@@ -28,9 +31,10 @@ modernize-use-override,
 modernize-use-using,
 *performance*,
 readability-avoid-const-params-in-decls,
+readability-const-return-type,
 readability-container-size-empty,
-readability-else-after-return,
 readability-delete-null-pointer,
+readability-else-after-return,
 readability-implicit-bool-conversion,
 readability-make-member-function-const,
 readability-misplaced-array-index,
@@ -43,6 +47,9 @@ readability-static-accessed-through-instance,
 readability-static-definition-in-anonymous-namespace,
 readability-string-compare,
 readability-uniqueptr-delete-release,
+-bugprone-exception-escape,
+-bugprone-reserved-identifier,
+-bugprone-unused-raii,
 '
 
 CheckOptions:

.github/CONTRIBUTING.md

@@ -68,8 +68,8 @@ nox -l
 # Run linters
 nox -s lint
 
-# Run tests
-nox -s tests
+# Run tests on Python 3.9
+nox -s tests-3.9
 
 # Build and preview docs
 nox -s docs -- serve

.github/ISSUE_TEMPLATE/bug-report.yml

@@ -0,0 +1,45 @@
+name: Bug Report
+description: File an issue about a bug
+title: "[BUG]: "
+labels: [triage]
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Maintainers will only make a best effort to triage PRs. Please do your best to make the issue as easy to act on as possible, and only open if clearly a problem with pybind11 (ask first if unsure).
+  - type: checkboxes
+    id: steps
+    attributes:
+      label: Required prerequisites
+      description: Make sure you've completed the following steps before submitting your issue -- thank you!
+      options:
+        - label: Make sure you've read the [documentation](https://pybind11.readthedocs.io). Your issue may be addressed there.
+          required: true
+        - label: Search the [issue tracker](https://github.com/pybind/pybind11/issues) and [Discussions](https:/pybind/pybind11/discussions) to verify that this hasn't already been reported. +1 or comment there if it has.
+          required: true
+        - label: Consider asking first in the [Gitter chat room](https://gitter.im/pybind/Lobby) or in a [Discussion](https:/pybind/pybind11/discussions/new).
+          required: false
+
+  - type: textarea
+    id: description
+    attributes:
+      label: Problem description
+      placeholder: >-
+        Provide a short description, state the expected behavior and what
+        actually happens. Include relevant information like what version of
+        pybind11 you are using, what system you are on, and any useful commands
+        / output.
+    validations:
+      required: true
+
+  - type: textarea
+    id: code
+    attributes:
+      label: Reproducible example code
+      placeholder: >-
+        The code should be minimal, have no external dependencies, isolate the
+        function(s) that cause breakage. Submit matched and complete C++ and
+        Python snippets that can be easily compiled and run to diagnose the
+        issue. If possible, make a PR with a new, failing test to give us a
+        starting point to work on!
+      render: text

.github/ISSUE_TEMPLATE/config.yml

@@ -1,5 +1,8 @@
 blank_issues_enabled: false
 contact_links:
+  - name: Ask a question
+    url: https://github.com/pybind/pybind11/discussions/new
+    about: Please ask and answer questions here, or propose new ideas.
   - name: Gitter room
     url: https://gitter.im/pybind/Lobby
     about: A room for discussing pybind11 with an active community

.github/pull_request_template.md

@@ -1,3 +1,7 @@
+<!--
+Title (above): please place [branch_name] at the beginning if you are targeting a branch other than master. *Do not target stable*.
+It is recommended to use conventional commit format, see conventionalcommits.org, but not required.
+-->
 ## Description
 
 <!-- Include relevant issues or PRs here, describe what changed and why -->

.github/workflows/ci.yml

@@ -75,7 +75,7 @@ jobs:
       run: brew install boost
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.9
+      uses: jwlawson/actions-setup-cmake@v1.11
 
     - name: Cache wheels
       if: runner.os == 'macOS'
@@ -144,6 +144,24 @@ jobs:
       if: "!(runner.os == 'Windows' && (matrix.python == 3.8 || matrix.python == 3.9 || matrix.python == '3.10-dev'))"
       run: cmake --build build2 --target cpptest
 
+    # Third build - C++17 mode with unstable ABI
+    - name: Configure (unstable ABI)
+      run: >
+        cmake -S . -B build3
+        -DPYBIND11_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_EIGEN=ON
+        -DCMAKE_CXX_STANDARD=17
+        -DPYBIND11_INTERNALS_VERSION=10000000
+        "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
+        ${{ matrix.args }}
+
+    - name: Build (unstable ABI)
+      run: cmake --build build3 -j 2
+
+    - name: Python tests (unstable ABI)
+      run: cmake --build build3 --target pytest
+
     - name: Interface test
       run: cmake --build build2 --target test_cmake_build
 
@@ -193,7 +211,7 @@ jobs:
         debug: ${{ matrix.python-debug }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.9
+      uses: jwlawson/actions-setup-cmake@v1.11
 
     - name: Valgrind cache
       if: matrix.valgrind
@@ -445,7 +463,7 @@ jobs:
       run: python3 -m pip install --upgrade pip
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.9
+      uses: jwlawson/actions-setup-cmake@v1.11
 
     - name: Configure
       shell: bash
@@ -594,14 +612,15 @@ jobs:
 
     - name: VAR_BUILD_TYPE 7
       if: matrix.centos == 7
-      run: echo Release > VAR_BUILD_TYPE
+      run: echo MinSizeRel > VAR_BUILD_TYPE
 
-    # Using Debug to avoid segfault that appeared around 2021-06-04,
+    # Using Release to avoid segfault that appeared around 2021-06-04,
     # apparently when the gcc version changed from 8.3 to 8.4.
     - name: VAR_BUILD_TYPE 8
       if: matrix.centos == 8
-      run: echo Debug > VAR_BUILD_TYPE
+      run: echo Release > VAR_BUILD_TYPE
 
+    # Temporally disabling EIGEN due to SSL issue in CentOS 7
     - name: Configure
       shell: bash
       run: >
@@ -664,7 +683,7 @@ jobs:
         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
       working-directory: /build-tests
 
-    - name: Run tests
+    - name: Python tests
       run: make pytest -j 2
       working-directory: /build-tests
 
@@ -738,7 +757,7 @@ jobs:
         architecture: x86
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.9
+      uses: jwlawson/actions-setup-cmake@v1.11
 
     - name: Prepare MSVC
       uses: ilammy/msvc-dev-cmd@v1.9.0
@@ -760,7 +779,7 @@ jobs:
     - name: Build C++11
       run: cmake --build build -j 2
 
-    - name: Run tests
+    - name: Python tests
       run: cmake --build build -t pytest
 
   win32-msvc2015:
@@ -784,7 +803,7 @@ jobs:
         python-version: ${{ matrix.python }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.9
+      uses: jwlawson/actions-setup-cmake@v1.11
 
     - name: Prepare MSVC
       uses: ilammy/msvc-dev-cmd@v1.9.0
@@ -838,7 +857,7 @@ jobs:
         python-version: ${{ matrix.python }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.9
+      uses: jwlawson/actions-setup-cmake@v1.11
 
     - name: Prepare env
       run: python -m pip install -r tests/requirements.txt --prefer-binary
@@ -861,32 +880,85 @@ jobs:
       run: cmake --build build -t check
 
   mingw:
+    name: "🐍 3 • windows-latest • ${{ matrix.sys }}"
     runs-on: windows-latest
     defaults:
       run:
         shell: msys2 {0}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - { sys: mingw64, env: x86_64 }
+          - { sys: mingw32, env: i686 }
     steps:
     - uses: msys2/setup-msys2@v2
       with:
+        msystem: ${{matrix.sys}}
         install: >-
-          mingw-w64-x86_64-gcc
-          mingw-w64-x86_64-python-pip
-          mingw-w64-x86_64-cmake
-          mingw-w64-x86_64-make
-          mingw-w64-x86_64-python-pytest
-          mingw-w64-x86_64-eigen3
-          mingw-w64-x86_64-boost
-          mingw-w64-x86_64-catch
+          git
+          mingw-w64-${{matrix.env}}-gcc
+          mingw-w64-${{matrix.env}}-python-pip
+          mingw-w64-${{matrix.env}}-python-numpy
+          mingw-w64-${{matrix.env}}-python-scipy
+          mingw-w64-${{matrix.env}}-cmake
+          mingw-w64-${{matrix.env}}-make
+          mingw-w64-${{matrix.env}}-python-pytest
+          mingw-w64-${{matrix.env}}-eigen3
+          mingw-w64-${{matrix.env}}-boost
+          mingw-w64-${{matrix.env}}-catch
 
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
 
-    - name: Configure
+    - name: Configure C++11
       # LTO leads to many undefined reference like
       # `pybind11::detail::function_call::function_call(pybind11::detail::function_call&&)
-      run: cmake -G "MinGW Makefiles" -S . -B build
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=11 -S . -B build
 
-    - name: Build
+    - name: Build C++11
       run: cmake --build build -j 2
 
-    - name: Python tests
-      run: cmake --build build --target pytest
+    - name: Python tests C++11
+      run: cmake --build build --target pytest -j 2
+
+    - name: C++11 tests
+      run: cmake --build build --target cpptest -j 2
+
+    - name: Interface test C++11
+      run: cmake --build build --target test_cmake_build
+
+    - name: Clean directory
+      run: git clean -fdx
+
+    - name: Configure C++14
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=14 -S . -B build2
+
+    - name: Build C++14
+      run: cmake --build build2 -j 2
+
+    - name: Python tests C++14
+      run: cmake --build build2 --target pytest -j 2
+
+    - name: C++14 tests
+      run: cmake --build build2 --target cpptest -j 2
+
+    - name: Interface test C++14
+      run: cmake --build build2 --target test_cmake_build
+
+    - name: Clean directory
+      run: git clean -fdx
+
+    - name: Configure C++17
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=17 -S . -B build3
+
+    - name: Build C++17
+      run: cmake --build build3 -j 2
+
+    - name: Python tests C++17
+      run: cmake --build build3 --target pytest -j 2
+
+    - name: C++17 tests
+      run: cmake --build build3 --target cpptest -j 2
+
+    - name: Interface test C++17
+      run: cmake --build build3 --target test_cmake_build