Git pre-commit hook to check code style of changed files right at commit time

10-flake8.py

from __future__ import print_function
"""
Pre-commit hook for PEP8 styling
Works well with flake8==3.0.4
"""

__author__ = 'Ivan Styazhkin <[email protected]>'

import subprocess
import sys


CHANGES_CMD = 'git diff --name-only --cached --diff-filter=ACM'.split()
GIT_HASH_CMD = 'git ls-files --stage'.split()
GIT_FILE_CONTENT_CMD = 'git cat-file blob'.split()

# Presonal preferences for ignoring
IGNORED_ERRORS = (
    'F403',  # 'from models import *' used; unable to detect undefined names
    'F405',  # assert_that may be undefined, or defined from star imports: hamcrest
)
MAX_LINE_LENGTH = 100
FLAKES_CMD = [
  'flake8',
  '-',
  '--ignore=%s' % ','.join(IGNORED_ERRORS),
  '--max-line-length=%s' % MAX_LINE_LENGTH,
]


def get_lines(stdout_text):
    """Assumes your console uses utf-8"""
    return stdout_text.strip().decode('utf-8').split('\n')


def get_python_changes():
    """Returns python filenames which are staged"""
    python_changes = get_lines(subprocess.check_output(CHANGES_CMD))
    return [s for s in python_changes if s.endswith('.py')]


def get_staged_file_content(filename):
    """Returns staged version of the file"""
    hash_line = subprocess.check_output(GIT_HASH_CMD + [filename])
    _, file_hash, _, _ = hash_line.split()
    return subprocess.check_output(GIT_FILE_CONTENT_CMD + [file_hash])


def main(stream):
    filename_list = get_python_changes()
    if not filename_list:
        return

    error_list = list()
    for filename in filename_list:
        content = get_staged_file_content(filename)
        pipe = subprocess.Popen(
            FLAKES_CMD,
            stdin=subprocess.PIPE,
            stdout=subprocess.PIPE,
        )
        pipe.stdin.write(content)
        out, _ = pipe.communicate()
        if out:
            error_list.extend([
                line.replace('stdin', filename)
                for line in get_lines(out)
            ])

    if not error_list:
        print('\033[92mCheck flake8: OK\033[0m')
        return

    print('\033[91mCheck %d files for flake8: %d errors\033[0m' % (len(filename_list), len(error_list)))
    for error in error_list:
        print(error)

    return 1


if __name__ == '__main__':
    exit(main(sys.stdout))