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/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/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