git pre-receive hook with checkstyle for java code checking

Today I have written a small python script for forcing the sun coding conventions in a small project. For checking the java source code I have used the checkstyle tool.

The following python script uses the git executable for creating a file list of all changed files, latest file revision only, and run checkstyle over it.

#!/usr/bin/env python

import subprocess
import sys
import tempfile
import shutil
import os
import errno

# variables for checkstyle
checkstyle = '/path/to/checkstyle.jar'
checkstyle_config = 'name_of_config.xml'

# implementing check_output for python < 2.7
if not hasattr(subprocess, 'check_output'):
    def check_output(*popenargs, **kwargs):
        if 'stdout' in kwargs:
            raise ValueError('stdout argument not allowed, it will be overridden.')
        process = subprocess.Popen(stdout=subprocess.PIPE, *popenargs, **kwargs)
        output, unused_err = process.communicate()
        retcode = process.poll()
        if retcode:
            cmd = kwargs.get("args")
            if cmd is None:
                cmd = popenargs[0]
            er = subprocess.CalledProcessError(retcode, cmd)
            er.output = output
            raise er
        return output
    subprocess.check_output = check_output


# helper for calling executables
def call(*args, **kwargs):
    return subprocess.check_output(*args, **kwargs).strip()


# helper for calling git
def call_git(cmd, *args, **kwargs):
    return call(['git'] + cmd, *args, **kwargs)


# get all new commits from stdin
def get_commits():
    commits = {}
    for line in sys.stdin:
        old, new, ref = line.strip().split(' ')
        if old == '0000000000000000000000000000000000000000':
            old = '4b825dc642cb6eb9a060e54bf8d69288fbee4904'

        if ref not in commits:
            commits[ref] = []
        commits[ref].append({
            'old': old,
            'new': new,
            'files': get_changed_files(old, new)
            })

    return commits


# get a list of changed files between to commits
def get_changed_files(old, new):
    return call_git(['diff', '--name-only', old, new]).split('\n')


# get filemode, object type (blob,tree,commit), hash for the given file at the
# given commit
def get_change_type(commit, filename):
    return call_git(['ls-tree', commit, filename]).split('\t')[0].split(' ')


commits = get_commits()

# use the latest file commit only
print "Cleaning up file list..."

files = {}
count = 0
for ref, data in commits.iteritems():
    files[ref] = {}
    for commit in data:
        for filename in commit['files']:
            files[ref][filename] = get_change_type(commit['new'], filename)
    count += len(files[ref])

print "%d Files to check in %d branches" % (count, len(files))

# create temporary dir and save a copy of the new files
tempdir = tempfile.mkdtemp('git_hook')
for ref, files in files.iteritems():
    for filename, data in files.iteritems():
        dname = os.path.dirname(filename)
        bname = os.path.basename(filename)
        try:
            os.makedirs(os.path.join(tempdir, dname))
        except OSError, exc:
            if exc.errno == errno.EEXIST:  # directory exists already
                pass
            else:
                raise

        with open(os.path.join(tempdir, dname, bname), 'w') as fp:
            fp.write(call_git(['cat-file', data[1], data[2]]))

try:
    # call checkstyle and print output
    print call(['java', '-jar', checkstyle, '-c', checkstyle_config, '-r', tempdir])
except subprocess.CalledProcessError, ex:
    print ex.output  # print checkstyle messages
    exit(1)
finally:
    # remove temporary directory
    shutil.rmtree(tempdir)

If you want to check java files only, you will have to add the following check between line 81 and 82 (make sure that you have 12 spaces before the if):

            if not filename.lower().endswith('.java'): continue

Place this file as pre-receive with execute flag in the hooks directory of your repository. The checkstyle configuration files have to be placed inside of your bare repository (or in the .git directory, if you have a workingcopy).

No bad code anymore :-)

BlueC0re