ci: GHA basic format & pre-commit (#2309)

.github/workflows/format.yml

+name: Format
+
+on:
+  workflow_dispatch:
+  pull_request:
+  push:
+    branches:
+    - master
+    - stable
+    - "v*"
+
+jobs:
+  pre-commit:
+    name: Format
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-python@v2
+    - uses: pre-commit/action@v2.0.0

.pre-commit-config.yaml

+repos:
+- repo: https://github.com/pre-commit/pre-commit-hooks
+  rev: v3.1.0
+  hooks:
+  - id: check-added-large-files
+  - id: check-case-conflict
+  - id: check-merge-conflict
+  - id: check-symlinks
+  - id: check-yaml
+  - id: debug-statements
+  - id: end-of-file-fixer
+  - id: mixed-line-ending
+  - id: requirements-txt-fixer
+  - id: trailing-whitespace
+  - id: fix-encoding-pragma
+
+- repo: https://github.com/Lucas-C/pre-commit-hooks
+  rev: v1.1.7
+  hooks:
+  - id: remove-tabs
+    exclude: (Makefile|debian/rules|.gitmodules)(\.in)?$
+
+- repo: https://gitlab.com/pycqa/flake8
+  rev: 3.8.2
+  hooks:
+  - id: flake8
+    additional_dependencies: [flake8-bugbear]
+    exclude: ^(docs/.*|tools/.*)$

CONTRIBUTING.md

@@ -27,11 +27,16 @@ adhere to the following rules to make the process as smooth as possible:
   do add value by themselves.
 * Add tests for any new functionality and run the test suite (``make pytest``)
   to ensure that no existing features break.
-* Please run ``flake8`` and ``tools/check-style.sh`` to check your code matches
-  the project style. (Note that ``check-style.sh`` requires ``gawk``.)
+* Please run [``pre-commit``][pre-commit] and ``tools/check-style.sh`` to check
+  your code matches the project style. (Note that ``check-style.sh`` requires
+  ``gawk``.) Use `pre-commit run --all-files` before committing (or use
+  installed-mode, check pre-commit docs) to verify your code passes before
+  pushing to save time.
 * This project has a strong focus on providing general solutions using a
   minimal amount of code, thus small pull requests are greatly preferred.
 
+[pre-commit]: https://pre-commit.com
+
 ### Licensing of contributions
 
 pybind11 is provided under a BSD-style license that can be found in the

docs/advanced/cast/index.rst

@@ -39,4 +39,3 @@ the last case of the above list.
    chrono
    eigen
    custom
-

docs/advanced/classes.rst

@@ -82,7 +82,7 @@ helper class that is defined as follows:
 
 The macro :c:macro:`PYBIND11_OVERLOAD_PURE` should be used for pure virtual
 functions, and :c:macro:`PYBIND11_OVERLOAD` should be used for functions which have
-a default implementation.  There are also two alternate macros 
+a default implementation.  There are also two alternate macros
 :c:macro:`PYBIND11_OVERLOAD_PURE_NAME` and :c:macro:`PYBIND11_OVERLOAD_NAME` which
 take a string-valued name argument between the *Parent class* and *Name of the
 function* slots, which defines the name of function in Python. This is required
@@ -1088,7 +1088,7 @@ Binding final classes
 
 Some classes may not be appropriate to inherit from. In C++11, classes can
 use the ``final`` specifier to ensure that a class cannot be inherited from.
-The ``py::is_final`` attribute can be used to ensure that Python classes 
+The ``py::is_final`` attribute can be used to ensure that Python classes
 cannot inherit from a specified type. The underlying C++ type does not need
 to be declared final.
 

docs/advanced/misc.rst

@@ -218,7 +218,7 @@ collected:
 
 Both approaches also expose a potentially dangerous ``_cleanup`` attribute in
 Python, which may be undesirable from an API standpoint (a premature explicit
-call from Python might lead to undefined behavior). Yet another approach that 
+call from Python might lead to undefined behavior). Yet another approach that
 avoids this issue involves weak reference with a cleanup callback:
 
 .. code-block:: cpp
@@ -283,9 +283,9 @@ work, it is important that all lines are indented consistently, i.e.:
         ----------
     )mydelimiter");
 
-By default, pybind11 automatically generates and prepends a signature to the docstring of a function 
+By default, pybind11 automatically generates and prepends a signature to the docstring of a function
 registered with ``module::def()`` and ``class_::def()``. Sometimes this
-behavior is not desirable, because you want to provide your own signature or remove 
+behavior is not desirable, because you want to provide your own signature or remove
 the docstring completely to exclude the function from the Sphinx documentation.
 The class ``options`` allows you to selectively suppress auto-generated signatures:
 
@@ -298,8 +298,8 @@ The class ``options`` allows you to selectively suppress auto-generated signatur
         m.def("add", [](int a, int b) { return a + b; }, "A function which adds two numbers");
     }
 
-Note that changes to the settings affect only function bindings created during the 
-lifetime of the ``options`` instance. When it goes out of scope at the end of the module's init function, 
+Note that changes to the settings affect only function bindings created during the
+lifetime of the ``options`` instance. When it goes out of scope at the end of the module's init function,
 the default settings are restored to prevent unwanted side effects.
 
 .. [#f4] http://www.sphinx-doc.org

docs/advanced/pycpp/object.rst

@@ -60,7 +60,7 @@ This example obtains a reference to the Python ``Decimal`` class.
 Calling Python functions
 ========================
 
-It is also possible to call Python classes, functions and methods 
+It is also possible to call Python classes, functions and methods
 via ``operator()``.
 
 .. code-block:: cpp
@@ -75,7 +75,7 @@ via ``operator()``.
     py::object makedirs = os.attr("makedirs");
     makedirs("/tmp/path/to/somewhere");
 
-One can convert the result obtained from Python to a pure C++ version 
+One can convert the result obtained from Python to a pure C++ version
 if a ``py::class_`` or type conversion is defined.
 
 .. code-block:: cpp
@@ -99,8 +99,8 @@ Python method.
     py::print(py::str(exp_pi));
 
 In the example above ``pi.attr("exp")`` is a *bound method*: it will always call
-the method for that same instance of the class. Alternately one can create an 
-*unbound method* via the Python class (instead of instance) and pass the ``self`` 
+the method for that same instance of the class. Alternately one can create an
+*unbound method* via the Python class (instead of instance) and pass the ``self``
 object explicitly, followed by other arguments.
 
 .. code-block:: cpp

docs/benchmark.py

+# -*- coding: utf-8 -*-
 import random
 import os
 import time

docs/benchmark.rst

@@ -93,5 +93,3 @@ favor.
 .. only:: latex
 
     .. image:: pybind11_vs_boost_python2.png
-
-

docs/conf.py

@@ -130,8 +130,8 @@ if not on_rtd:  # only import and set the theme if we're building docs locally
 else:
     html_context = {
         'css_files': [
-            '//media.readthedocs.org/css/sphinx_rtd_theme.css',            
-            '//media.readthedocs.org/css/readthedocs-doc-embed.css',    
+            '//media.readthedocs.org/css/sphinx_rtd_theme.css',
+            '//media.readthedocs.org/css/readthedocs-doc-embed.css',
             '_static/theme_overrides.css'
         ]
     }

docs/limitations.rst

@@ -17,4 +17,3 @@ These features could be implemented but would lead to a significant increase in
 complexity. I've decided to draw the line here to keep this project simple and
 compact. Users who absolutely require these features are encouraged to fork
 pybind11.
-

pybind11/__init__.py

+# -*- coding: utf-8 -*-
 from ._version import version_info, __version__  # noqa: F401 imported but unused
 
 

pybind11/__main__.py

+# -*- coding: utf-8 -*-
 from __future__ import print_function
 
 import argparse

pybind11/_version.py

+# -*- coding: utf-8 -*-
 version_info = (2, 5, 'dev1')
 __version__ = '.'.join(map(str, version_info))

setup.py

 #!/usr/bin/env python
+# -*- coding: utf-8 -*-
 
 # Setup script for PyPI; use CMakeFile.txt to build extension modules
 

tests/conftest.py

+# -*- coding: utf-8 -*-
 """pytest configuration
 
 Extends output capture as needed by pybind11: ignore constructors, optional unordered lines.

tests/constructor_stats.h

@@ -273,4 +273,3 @@ template <class T, typename... Values> void print_values(T *inst, Values &&...va
     print_constr_details(inst, ":", values...);
     track_values(inst, values...);
 }
-

tests/test_async.py

+# -*- coding: utf-8 -*-
 import asyncio
 import pytest
 from pybind11_tests import async_module as m

tests/test_buffers.py

+# -*- coding: utf-8 -*-
 import io
 import struct
 import sys

tests/test_builtin_casters.py

-# Python < 3 needs this: coding=utf-8
+# -*- coding: utf-8 -*-
 import pytest
 
 from pybind11_tests import builtin_casters as m