Pre-commit hooks for python development

flake8-check

#!/usr/bin/env python
#
# flake8-checks the staged versions of any changed python files
import os.path
import subprocess
import tempfile
import shutil
import atexit

tempdir = tempfile.mkdtemp()
atexit.register(lambda: shutil.rmtree(tempdir))

diff = subprocess.Popen(['git', 'diff', '--cached', '--name-only',
                         '--diff-filter=ACM'],
                        stdout=subprocess.PIPE)

all_changed_files = diff.communicate()[0].split("\n")
changed_py_files = [filename for filename in all_changed_files
                    if filename.endswith(".py")]

subprocess.check_call(
    ['git', 'checkout-index', '--prefix=%s/' % tempdir, '-f'] +
    changed_py_files)
flake8_exit_status = subprocess.call(
    ['flake8'] +
    [os.path.join(tempdir, fname) for fname in changed_py_files])

# errors already printed, if any; just propagate the error status up
exit(flake8_exit_status)

json-syntax-check

#!/usr/bin/env python
#
# Syntax checks the staged versions of any changed .json files.
#
# Exists because I suck at editing JSON by hand. Seriously, it's 2013; why
# can't I have trailing commas?

import sys
import os.path
import subprocess
import tempfile
import json
import shutil
import atexit

tempdir = tempfile.mkdtemp()
atexit.register(lambda: shutil.rmtree(tempdir))

diff = subprocess.Popen(['git', 'diff', '--cached', '--name-only',
                         '--diff-filter=ACM'],
                        stdout=subprocess.PIPE)

all_changed_files = diff.communicate()[0].split("\n")
changed_json_files = [filename for filename in all_changed_files
                      if filename.endswith('.json')]

ci_args = ['git', 'checkout-index', '--prefix=%s/' % tempdir, '-f']
ci_args.extend(changed_json_files)
subprocess.check_call(ci_args)

exitstatus = 0
for filename in changed_json_files:
    with open(os.path.join(tempdir, filename)) as jsonfh:
        print "Syntax checking the staged version of %s" % filename
        try:
            json.loads(jsonfh.read())
        except ValueError:
            sys.stderr.write("%s is not a syntactically valid JSON file. "
                             "Preventing checkin.\n" % filename)
            sys.stderr.write("If you really need to commit a busted .json "
                             "file, use 'git commit --no-verify'\n")
            exitstatus = 1

exit(exitstatus)

pre-commit

#!/bin/sh

for fname in .git/hooks/pre-commit.d/*; do
    if test -x "$fname"; then
        if ! "$fname"; then
            echo
            echo "*** Error running $fname; commit aborted ***"
            echo
            exit 1
        fi
    fi
done