Merge 'upstream/master' (9c0aa69937)

.appveyor.yml

@@ -19,11 +19,11 @@ install:
     if ($env:PLATFORM -eq "x64") { $env:PYTHON = "$env:PYTHON-x64" }
     $env:PATH = "C:\Python$env:PYTHON\;C:\Python$env:PYTHON\Scripts\;$env:PATH"
     python -W ignore -m pip install --upgrade pip wheel
-    python -W ignore -m pip install pytest numpy --no-warn-script-location
+    python -W ignore -m pip install pytest numpy --no-warn-script-location pytest-timeout
 - ps: |
-    Start-FileDownload 'http://bitbucket.org/eigen/eigen/get/3.3.3.zip'
-    7z x 3.3.3.zip -y > $null
-    $env:CMAKE_INCLUDE_PATH = "eigen-eigen-67e894c6cd8f;$env:CMAKE_INCLUDE_PATH"
+    Start-FileDownload 'https://gitlab.com/libeigen/eigen/-/archive/3.3.7/eigen-3.3.7.zip'
+    7z x eigen-3.3.7.zip -y > $null
+    $env:CMAKE_INCLUDE_PATH = "eigen-3.3.7;$env:CMAKE_INCLUDE_PATH"
 build_script:
 - cmake -G "%CMAKE_GENERATOR%" -A "%CMAKE_ARCH%"
     -DCMAKE_CXX_STANDARD=14

.clang-format

@@ -0,0 +1,21 @@
+---
+# See all possible options and defaults with:
+# clang-format --style=llvm --dump-config
+BasedOnStyle: LLVM
+AccessModifierOffset: -4
+AlignConsecutiveAssignments: true
+AlwaysBreakTemplateDeclarations: Yes
+BinPackArguments: false
+BinPackParameters: false
+BreakBeforeBinaryOperators: All
+BreakConstructorInitializers: BeforeColon
+ColumnLimit: 99
+IndentCaseLabels: true
+IndentPPDirectives: AfterHash
+IndentWidth: 4
+Language: Cpp
+SpaceAfterCStyleCast: true
+# SpaceInEmptyBlock: true # too new
+Standard: Cpp11
+TabWidth: 4
+...

.clang-tidy

@@ -0,0 +1,13 @@
+FormatStyle: file
+
+Checks: '
+llvm-namespace-comment,
+modernize-use-override,
+readability-container-size-empty,
+modernize-use-using,
+modernize-use-equals-default,
+modernize-use-auto,
+modernize-use-emplace,
+'
+
+HeaderFilterRegex: 'pybind11/.*h'

.github/CONTRIBUTING.md

@@ -126,14 +126,26 @@ cmake --build build --target check
 `--target` can be spelled `-t` in CMake 3.15+. You can also run individual
 tests with these targets:
 
-* `pytest`: Python tests only
+* `pytest`: Python tests only, using the
+[pytest](https://docs.pytest.org/en/stable/) framework
 * `cpptest`: C++ tests only
 * `test_cmake_build`: Install / subdirectory tests
 
 If you want to build just a subset of tests, use
 `-DPYBIND11_TEST_OVERRIDE="test_callbacks.cpp;test_pickling.cpp"`. If this is
 empty, all tests will be built.
 
+You may also pass flags to the `pytest` target by editing `tests/pytest.ini` or
+by using the `PYTEST_ADDOPTS` environment variable
+(see [`pytest` docs](https://docs.pytest.org/en/2.7.3/customize.html#adding-default-options)). As an example:
+
+```bash
+env PYTEST_ADDOPTS="--capture=no --exitfirst" \
+    cmake --build build --target pytest
+# Or using abbreviated flags
+env PYTEST_ADDOPTS="-s -x" cmake --build build --target pytest
+```
+
 ### Formatting
 
 All formatting is handled by pre-commit.
@@ -164,7 +176,182 @@ name, pre-commit):
 pre-commit install
 ```
 
+### Clang-Format
+
+As of v2.6.2, pybind11 ships with a [`clang-format`][clang-format]
+configuration file at the top level of the repo (the filename is
+`.clang-format`). Currently, formatting is NOT applied automatically, but
+manually using `clang-format` for newly developed files is highly encouraged.
+To check if a file needs formatting:
+
+```bash
+clang-format -style=file --dry-run some.cpp
+```
+
+The output will show things to be fixed, if any. To actually format the file:
+
+```bash
+clang-format -style=file -i some.cpp
+```
+
+Note that the `-style-file` option searches the parent directories for the
+`.clang-format` file, i.e. the commands above can be run in any subdirectory
+of the pybind11 repo.
+
+### Clang-Tidy
+
+[`clang-tidy`][clang-tidy] performs deeper static code analyses and is
+more complex to run, compared to `clang-format`, but support for `clang-tidy`
+is built into the pybind11 CMake configuration. To run `clang-tidy`, the
+following recipe should work. Files will be modified in place, so you can
+use git to monitor the changes.
+
+```bash
+docker run --rm -v $PWD:/pybind11 -it silkeh/clang:10
+apt-get update && apt-get install python3-dev python3-pytest
+cmake -S pybind11/ -B build -DCMAKE_CXX_CLANG_TIDY="$(which clang-tidy);-fix"
+cmake --build build
+```
+
+### Include what you use
+
+To run include what you use, install (`brew install include-what-you-use` on
+macOS), then run:
+
+```bash
+cmake -S . -B build-iwyu -DCMAKE_CXX_INCLUDE_WHAT_YOU_USE=$(which include-what-you-use)
+cmake --build build
+```
+
+The report is sent to stderr; you can pipe it into a file if you wish.
+
+### Build recipes
+
+This builds with the Intel compiler (assuming it is in your path, along with a
+recent CMake and Python 3):
+
+```bash
+python3 -m venv venv
+. venv/bin/activate
+pip install pytest
+cmake -S . -B build-intel -DCMAKE_CXX_COMPILER=$(which icpc) -DDOWNLOAD_CATCH=ON -DDOWNLOAD_EIGEN=ON -DPYBIND11_WERROR=ON
+```
+
+This will test the PGI compilers:
+
+```bash
+docker run --rm -it -v $PWD:/pybind11 nvcr.io/hpc/pgi-compilers:ce
+apt-get update && apt-get install -y python3-dev python3-pip python3-pytest
+wget -qO- "https://cmake.org/files/v3.18/cmake-3.18.2-Linux-x86_64.tar.gz" | tar --strip-components=1 -xz -C /usr/local
+cmake -S pybind11/ -B build
+cmake --build build
+```
+
+### Explanation of the SDist/wheel building design
+
+> These details below are _only_ for packaging the Python sources from git. The
+> SDists and wheels created do not have any extra requirements at all and are
+> completely normal.
+
+The main objective of the packaging system is to create SDists (Python's source
+distribution packages) and wheels (Python's binary distribution packages) that
+include everything that is needed to work with pybind11, and which can be
+installed without any additional dependencies. This is more complex than it
+appears: in order to support CMake as a first class language even when using
+the PyPI package, they must include the _generated_ CMake files (so as not to
+require CMake when installing the `pybind11` package itself). They should also
+provide the option to install to the "standard" location
+(`<ENVROOT>/include/pybind11` and `<ENVROOT>/share/cmake/pybind11`) so they are
+easy to find with CMake, but this can cause problems if you are not an
+environment or using ``pyproject.toml`` requirements. This was solved by having
+two packages; the "nice" pybind11 package that stores the includes and CMake
+files inside the package, that you get access to via functions in the package,
+and a `pybind11-global` package that can be included via `pybind11[global]` if
+you want the more invasive but discoverable file locations.
+
+If you want to install or package the GitHub source, it is best to have Pip 10
+or newer on Windows, macOS, or Linux (manylinux1 compatible, includes most
+distributions).  You can then build the SDists, or run any procedure that makes
+SDists internally, like making wheels or installing.
+
+
+```bash
+# Editable development install example
+python3 -m pip install -e .
+```
+
+Since Pip itself does not have an `sdist` command (it does have `wheel` and
+`install`), you may want to use the upcoming `build` package:
+
+```bash
+python3 -m pip install build
+
+# Normal package
+python3 -m build -s .
+
+# Global extra
+PYBIND11_GLOBAL_SDIST=1 python3 -m build -s .
+```
+
+If you want to use the classic "direct" usage of `python setup.py`, you will
+need CMake 3.15+ and either `make` or `ninja` preinstalled (possibly via `pip
+install cmake ninja`), since directly running Python on `setup.py` cannot pick
+up and install `pyproject.toml` requirements. As long as you have those two
+things, though, everything works the way you would expect:
+
+```bash
+# Normal package
+python3 setup.py sdist
+
+# Global extra
+PYBIND11_GLOBAL_SDIST=1 python3 setup.py sdist
+```
+
+A detailed explanation of the build procedure design for developers wanting to
+work on or maintain the packaging system is as follows:
+
+#### 1. Building from the source directory
+
+When you invoke any `setup.py` command from the source directory, including
+`pip wheel .` and `pip install .`, you will activate a full source build. This
+is made of the following steps:
+
+1. If the tool is PEP 518 compliant, like Pip 10+, it will create a temporary
+   virtual environment and install the build requirements (mostly CMake) into
+   it. (if you are not on Windows, macOS, or a manylinux compliant system, you
+   can disable this with `--no-build-isolation` as long as you have CMake 3.15+
+   installed)
+2. The environment variable `PYBIND11_GLOBAL_SDIST` is checked - if it is set
+   and truthy, this will be make the accessory `pybind11-global` package,
+   instead of the normal `pybind11` package. This package is used for
+   installing the files directly to your environment root directory, using
+   `pybind11[global]`.
+2. `setup.py` reads the version from `pybind11/_version.py` and verifies it
+   matches `includes/pybind11/detail/common.h`.
+3. CMake is run with `-DCMAKE_INSTALL_PREIFX=pybind11`. Since the CMake install
+   procedure uses only relative paths and is identical on all platforms, these
+   files are valid as long as they stay in the correct relative position to the
+   includes. `pybind11/share/cmake/pybind11` has the CMake files, and
+   `pybind11/include` has the includes. The build directory is discarded.
+4. Simpler files are placed in the SDist: `tools/setup_*.py.in`,
+   `tools/pyproject.toml` (`main` or `global`)
+5. The package is created by running the setup function in the
+   `tools/setup_*.py`.  `setup_main.py` fills in Python packages, and
+   `setup_global.py` fills in only the data/header slots.
+6. A context manager cleans up the temporary CMake install directory (even if
+   an error is thrown).
+
+### 2. Building from SDist
+
+Since the SDist has the rendered template files in `tools` along with the
+includes and CMake files in the correct locations, the builds are completely
+trivial and simple. No extra requirements are required. You can even use Pip 9
+if you really want to.
+
+
 [pre-commit]: https://pre-commit.com
+[clang-format]: https://clang.llvm.org/docs/ClangFormat.html
+[clang-tidy]: https://clang.llvm.org/extra/clang-tidy/
 [pybind11.readthedocs.org]: http://pybind11.readthedocs.org/en/latest
 [issue tracker]: https://github.com/pybind/pybind11/issues
 [gitter]: https://gitter.im/pybind/Lobby

.github/dependabot.yml

@@ -0,0 +1,16 @@
+version: 2
+updates:
+  # Maintain dependencies for GitHub Actions
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"
+    ignore:
+      # Official actions have moving tags like v1
+      # that are used, so they don't need updates here
+      - dependency-name: "actions/checkout"
+      - dependency-name: "actions/setup-python"
+      - dependency-name: "actions/cache"
+      - dependency-name: "actions/upload-artifact"
+      - dependency-name: "actions/download-artifact"
+      - dependency-name: "actions/labeler"

.github/labeler.yml

@@ -0,0 +1,8 @@
+docs:
+- any:
+  - 'docs/**/*.rst'
+  - '!docs/changelog.rst'
+  - '!docs/upgrade.rst'
+
+ci:
+- '.github/workflows/*.yml'

.github/labeler_merged.yml

@@ -0,0 +1,3 @@
+needs changelog:
+- all:
+  - '!docs/changelog.rst'

.github/pull_request_template.md

@@ -0,0 +1,15 @@
+## Description
+
+<!-- Include relevant issues or PRs here, describe what changed and why -->
+
+
+## Suggested changelog entry:
+
+<!-- Fill in the below block with the expected RestructuredText entry. Delete if no entry needed;
+     but do not delete header or rst block if an entry is needed! Will be collected via a script. -->
+
+```rst
+
+```
+
+<!-- If the upgrade guide needs updating, note that here too -->