presubmit_support.py

#!/usr/bin/env python
# Copyright (c) 2012 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Enables directory-specific presubmit checks to run at upload and/or commit.
"""

__version__ = '1.8.0'

# TODO(joi) Add caching where appropriate/needed. The API is designed to allow
# caching (between all different invocations of presubmit scripts for a given
# change). We should add it as our presubmit scripts start feeling slow.

import cpplint
import cPickle  # Exposed through the API.
import cStringIO  # Exposed through the API.
import contextlib
import fnmatch  # Exposed through the API.
import glob
import inspect
import itertools
import json  # Exposed through the API.
import logging
import marshal  # Exposed through the API.
import multiprocessing
import optparse
import os  # Somewhat exposed through the API.
import pickle  # Exposed through the API.
import random
import re  # Exposed through the API.
import sys  # Parts exposed through API.
import tempfile  # Exposed through the API.
import time
import traceback  # Exposed through the API.
import types
import unittest  # Exposed through the API.
import urllib2  # Exposed through the API.
import urlparse
from warnings import warn

# Local imports.
import auth
import fix_encoding
import gclient_utils
import gerrit_util
import owners
import presubmit_canned_checks
import rietveld
import scm
import subprocess2 as subprocess  # Exposed through the API.


# Ask for feedback only once in program lifetime.
_ASKED_FOR_FEEDBACK = False


class PresubmitFailure(Exception):
  pass


class CommandData(object):
  def __init__(self, name, cmd, kwargs, message):
    self.name = name
    self.cmd = cmd
    self.kwargs = kwargs
    self.message = message
    self.info = None


def normpath(path):
  '''Version of os.path.normpath that also changes backward slashes to
  forward slashes when not running on Windows.
  '''
  # This is safe to always do because the Windows version of os.path.normpath
  # will replace forward slashes with backward slashes.
  path = path.replace(os.sep, '/')
  return os.path.normpath(path)


def _RightHandSideLinesImpl(affected_files):
  """Implements RightHandSideLines for InputApi and GclChange."""
  for af in affected_files:
    lines = af.ChangedContents()
    for line in lines:
      yield (af, line[0], line[1])


class PresubmitOutput(object):
  def __init__(self, input_stream=None, output_stream=None):
    self.input_stream = input_stream
    self.output_stream = output_stream
    self.reviewers = []
    self.written_output = []
    self.error_count = 0

  def prompt_yes_no(self, prompt_string):
    self.write(prompt_string)
    if self.input_stream:
      response = self.input_stream.readline().strip().lower()
      if response not in ('y', 'yes'):
        self.fail()
    else:
      self.fail()

  def fail(self):
    self.error_count += 1

  def should_continue(self):
    return not self.error_count

  def write(self, s):
    self.written_output.append(s)
    if self.output_stream:
      self.output_stream.write(s)

  def getvalue(self):
    return ''.join(self.written_output)


# Top level object so multiprocessing can pickle
# Public access through OutputApi object.
class _PresubmitResult(object):
  """Base class for result objects."""
  fatal = False
  should_prompt = False

  def __init__(self, message, items=None, long_text=''):
    """
    message: A short one-line message to indicate errors.
    items: A list of short strings to indicate where errors occurred.
    long_text: multi-line text output, e.g. from another tool
    """
    self._message = message
    self._items = items or []
    if items:
      self._items = items
    self._long_text = long_text.rstrip()

  def handle(self, output):
    output.write(self._message)
    output.write('\n')
    for index, item in enumerate(self._items):
      output.write('  ')
      # Write separately in case it's unicode.
      output.write(str(item))
      if index < len(self._items) - 1:
        output.write(' \\')
      output.write('\n')
    if self._long_text:
      output.write('\n***************\n')
      # Write separately in case it's unicode.
      output.write(self._long_text)
      output.write('\n***************\n')
    if self.fatal:
      output.fail()


# Top level object so multiprocessing can pickle
# Public access through OutputApi object.
class _PresubmitError(_PresubmitResult):
  """A hard presubmit error."""
  fatal = True


# Top level object so multiprocessing can pickle
# Public access through OutputApi object.
class _PresubmitPromptWarning(_PresubmitResult):
  """An warning that prompts the user if they want to continue."""
  should_prompt = True


# Top level object so multiprocessing can pickle
# Public access through OutputApi object.
class _PresubmitNotifyResult(_PresubmitResult):
  """Just print something to the screen -- but it's not even a warning."""
  pass


# Top level object so multiprocessing can pickle
# Public access through OutputApi object.
class _MailTextResult(_PresubmitResult):
  """A warning that should be included in the review request email."""
  def __init__(self, *args, **kwargs):
    super(_MailTextResult, self).__init__()
    raise NotImplementedError()

class GerritAccessor(object):
  """Limited Gerrit functionality for canned presubmit checks to work.

  To avoid excessive Gerrit calls, caches the results.
  """

  def __init__(self, host):
    self.host = host
    self.cache = {}

  def _FetchChangeDetail(self, issue):
    # Separate function to be easily mocked in tests.
    return gerrit_util.GetChangeDetail(
        self.host, str(issue),
        ['ALL_REVISIONS', 'DETAILED_LABELS'])

  def GetChangeInfo(self, issue):
    """Returns labels and all revisions (patchsets) for this issue.

    The result is a dictionary according to Gerrit REST Api.
    https://gerrit-review.googlesource.com/Documentation/rest-api.html

    However, API isn't very clear what's inside, so see tests for example.
    """
    assert issue
    cache_key = int(issue)
    if cache_key not in self.cache:
      self.cache[cache_key] = self._FetchChangeDetail(issue)
    return self.cache[cache_key]

  def GetChangeDescription(self, issue, patchset=None):
    """If patchset is none, fetches current patchset."""
    info = self.GetChangeInfo(issue)
    # info is a reference to cache. We'll modify it here adding description to
    # it to the right patchset, if it is not yet there.

    # Find revision info for the patchset we want.
    if patchset is not None:
      for rev, rev_info in info['revisions'].iteritems():
        if str(rev_info['_number']) == str(patchset):
          break
      else:
        raise Exception('patchset %s doesn\'t exist in issue %s' % (
            patchset, issue))
    else:
      rev = info['current_revision']
      rev_info = info['revisions'][rev]

    # Updates revision info, which is part of cached issue info.
    if 'real_description' not in rev_info:
      rev_info['real_description'] = (
          gerrit_util.GetChangeDescriptionFromGitiles(
              rev_info['fetch']['http']['url'], rev))
    return rev_info['real_description']

  def GetChangeOwner(self, issue):
    return self.GetChangeInfo(issue)['owner']['email']

  def GetChangeReviewers(self, issue, approving_only=True):
    cr = self.GetChangeInfo(issue)['labels']['Code-Review']
    max_value = max(int(k) for k in cr['values'].keys())
    return [r['email'] for r in cr['all']
            if not approving_only or r.get('value', 0) == max_value]


class OutputApi(object):
  """An instance of OutputApi gets passed to presubmit scripts so that they
  can output various types of results.
  """
  PresubmitResult = _PresubmitResult
  PresubmitError = _PresubmitError
  PresubmitPromptWarning = _PresubmitPromptWarning
  PresubmitNotifyResult = _PresubmitNotifyResult
  MailTextResult = _MailTextResult

  def __init__(self, is_committing):
    self.is_committing = is_committing

  def PresubmitPromptOrNotify(self, *args, **kwargs):
    """Warn the user when uploading, but only notify if committing."""
    if self.is_committing:
      return self.PresubmitNotifyResult(*args, **kwargs)
    return self.PresubmitPromptWarning(*args, **kwargs)


class InputApi(object):
  """An instance of this object is passed to presubmit scripts so they can
  know stuff about the change they're looking at.
  """
  # Method could be a function
  # pylint: disable=R0201

  # File extensions that are considered source files from a style guide
  # perspective. Don't modify this list from a presubmit script!
  #
  # Files without an extension aren't included in the list. If you want to
  # filter them as source files, add r"(^|.*?[\\\/])[^.]+$" to the white list.
  # Note that ALL CAPS files are black listed in DEFAULT_BLACK_LIST below.
  DEFAULT_WHITE_LIST = (
      # C++ and friends
      r".+\.c$", r".+\.cc$", r".+\.cpp$", r".+\.h$", r".+\.m$", r".+\.mm$",
      r".+\.inl$", r".+\.asm$", r".+\.hxx$", r".+\.hpp$", r".+\.s$", r".+\.S$",
      # Scripts
      r".+\.js$", r".+\.py$", r".+\.sh$", r".+\.rb$", r".+\.pl$", r".+\.pm$",
      # Other
      r".+\.java$", r".+\.mk$", r".+\.am$", r".+\.css$"
  )

  # Path regexp that should be excluded from being considered containing source
  # files. Don't modify this list from a presubmit script!
  DEFAULT_BLACK_LIST = (
      r"testing_support[\\\/]google_appengine[\\\/].*",
      r".*\bexperimental[\\\/].*",
      # Exclude third_party/.* but NOT third_party/WebKit (crbug.com/539768).
      r".*\bthird_party[\\\/](?!WebKit[\\\/]).*",
      # Output directories (just in case)
      r".*\bDebug[\\\/].*",
      r".*\bRelease[\\\/].*",
      r".*\bxcodebuild[\\\/].*",
      r".*\bout[\\\/].*",
      # All caps files like README and LICENCE.
      r".*\b[A-Z0-9_]{2,}$",
      # SCM (can happen in dual SCM configuration). (Slightly over aggressive)
      r"(|.*[\\\/])\.git[\\\/].*",
      r"(|.*[\\\/])\.svn[\\\/].*",
      # There is no point in processing a patch file.
      r".+\.diff$",
      r".+\.patch$",
  )

  def __init__(self, change, presubmit_path, is_committing,
      rietveld_obj, verbose, gerrit_obj=None, dry_run=None):
    """Builds an InputApi object.

    Args:
      change: A presubmit.Change object.
      presubmit_path: The path to the presubmit script being processed.
      is_committing: True if the change is about to be committed.
      rietveld_obj: rietveld.Rietveld client object
      gerrit_obj: provides basic Gerrit codereview functionality.
      dry_run: if true, some Checks will be skipped.
    """
    # Version number of the presubmit_support script.
    self.version = [int(x) for x in __version__.split('.')]
    self.change = change
    self.is_committing = is_committing
    self.rietveld = rietveld_obj
    self.gerrit = gerrit_obj
    self.dry_run = dry_run
    # TBD
    self.host_url = 'http://codereview.chromium.org'
    if self.rietveld:
      self.host_url = self.rietveld.url

    # We expose various modules and functions as attributes of the input_api
    # so that presubmit scripts don't have to import them.
    self.basename = os.path.basename
    self.cPickle = cPickle
    self.cpplint = cpplint
    self.cStringIO = cStringIO
    self.fnmatch = fnmatch
    self.glob = glob.glob
    self.json = json
    self.logging = logging.getLogger('PRESUBMIT')
    self.os_listdir = os.listdir
    self.os_walk = os.walk
    self.os_path = os.path
    self.os_stat = os.stat
    self.pickle = pickle
    self.marshal = marshal
    self.re = re
    self.subprocess = subprocess
    self.tempfile = tempfile
    self.time = time
    self.traceback = traceback
    self.unittest = unittest
    self.urllib2 = urllib2

    # To easily fork python.
    self.python_executable = sys.executable
    self.environ = os.environ

    # InputApi.platform is the platform you're currently running on.
    self.platform = sys.platform

    self.cpu_count = multiprocessing.cpu_count()

    # this is done here because in RunTests, the current working directory has
    # changed, which causes Pool() to explode fantastically when run on windows
    # (because it tries to load the __main__ module, which imports lots of
    # things relative to the current working directory).
    self._run_tests_pool = multiprocessing.Pool(self.cpu_count)

    # The local path of the currently-being-processed presubmit script.
    self._current_presubmit_path = os.path.dirname(presubmit_path)

    # We carry the canned checks so presubmit scripts can easily use them.
    self.canned_checks = presubmit_canned_checks

    # TODO(dpranke): figure out a list of all approved owners for a repo
    # in order to be able to handle wildcard OWNERS files?
    self.owners_db = owners.Database(change.RepositoryRoot(),
        fopen=file, os_path=self.os_path)
    self.verbose = verbose
    self.Command = CommandData

    # Replace <hash_map> and <hash_set> as headers that need to be included
    # with "base/containers/hash_tables.h" instead.
    # Access to a protected member _XX of a client class
    # pylint: disable=W0212
    self.cpplint._re_pattern_templates = [
      (a, b, 'base/containers/hash_tables.h')
        if header in ('<hash_map>', '<hash_set>') else (a, b, header)
      for (a, b, header) in cpplint._re_pattern_templates
    ]

  def PresubmitLocalPath(self):
    """Returns the local path of the presubmit script currently being run.

    This is useful if you don't want to hard-code absolute paths in the
    presubmit script.  For example, It can be used to find another file
    relative to the PRESUBMIT.py script, so the whole tree can be branched and
    the presubmit script still works, without editing its content.
    """
    return self._current_presubmit_path

  def DepotToLocalPath(self, depot_path):
    """Translate a depot path to a local path (relative to client root).

    Args:
      Depot path as a string.

    Returns:
      The local path of the depot path under the user's current client, or None
      if the file is not mapped.

      Remember to check for the None case and show an appropriate error!
    """
    return scm.SVN.CaptureLocalInfo([depot_path], self.change.RepositoryRoot()
        ).get('Path')

  def LocalToDepotPath(self, local_path):
    """Translate a local path to a depot path.

    Args:
      Local path (relative to current directory, or absolute) as a string.

    Returns:
      The depot path (SVN URL) of the file if mapped, otherwise None.
    """
    return scm.SVN.CaptureLocalInfo([local_path], self.change.RepositoryRoot()
        ).get('URL')

  def AffectedFiles(self, include_dirs=False, include_deletes=True,
                    file_filter=None):
    """Same as input_api.change.AffectedFiles() except only lists files
    (and optionally directories) in the same directory as the current presubmit
    script, or subdirectories thereof.
    """
    dir_with_slash = normpath("%s/" % self.PresubmitLocalPath())
    if len(dir_with_slash) == 1:
      dir_with_slash = ''

    return filter(
        lambda x: normpath(x.AbsoluteLocalPath()).startswith(dir_with_slash),
        self.change.AffectedFiles(include_dirs, include_deletes, file_filter))

  def LocalPaths(self, include_dirs=False):
    """Returns local paths of input_api.AffectedFiles()."""
    paths = [af.LocalPath() for af in self.AffectedFiles(include_dirs)]
    logging.debug("LocalPaths: %s", paths)
    return paths

  def AbsoluteLocalPaths(self, include_dirs=False):
    """Returns absolute local paths of input_api.AffectedFiles()."""
    return [af.AbsoluteLocalPath() for af in self.AffectedFiles(include_dirs)]

  def ServerPaths(self, include_dirs=False):
    """Returns server paths of input_api.AffectedFiles()."""
    return [af.ServerPath() for af in self.AffectedFiles(include_dirs)]

  def AffectedTextFiles(self, include_deletes=None):
    """Same as input_api.change.AffectedTextFiles() except only lists files
    in the same directory as the current presubmit script, or subdirectories
    thereof.
    """
    if include_deletes is not None:
      warn("AffectedTextFiles(include_deletes=%s)"
               " is deprecated and ignored" % str(include_deletes),
           category=DeprecationWarning,
           stacklevel=2)
    return filter(lambda x: x.IsTextFile(),
                  self.AffectedFiles(include_dirs=False, include_deletes=False))

  def FilterSourceFile(self, affected_file, white_list=None, black_list=None):
    """Filters out files that aren't considered "source file".

    If white_list or black_list is None, InputApi.DEFAULT_WHITE_LIST
    and InputApi.DEFAULT_BLACK_LIST is used respectively.

    The lists will be compiled as regular expression and
    AffectedFile.LocalPath() needs to pass both list.

    Note: Copy-paste this function to suit your needs or use a lambda function.
    """
    def Find(affected_file, items):
      local_path = affected_file.LocalPath()
      for item in items:
        if self.re.match(item, local_path):
          logging.debug("%s matched %s" % (item, local_path))
          return True
      return False
    return (Find(affected_file, white_list or self.DEFAULT_WHITE_LIST) and
            not Find(affected_file, black_list or self.DEFAULT_BLACK_LIST))

  def AffectedSourceFiles(self, source_file):
    """Filter the list of AffectedTextFiles by the function source_file.

    If source_file is None, InputApi.FilterSourceFile() is used.
    """
    if not source_file:
      source_file = self.FilterSourceFile
    return filter(source_file, self.AffectedTextFiles())

  def RightHandSideLines(self, source_file_filter=None):
    """An iterator over all text lines in "new" version of changed files.

    Only lists lines from new or modified text files in the change that are
    contained by the directory of the currently executing presubmit script.

    This is useful for doing line-by-line regex checks, like checking for
    trailing whitespace.

    Yields:
      a 3 tuple:
        the AffectedFile instance of the current file;
        integer line number (1-based); and
        the contents of the line as a string.

    Note: The carriage return (LF or CR) is stripped off.
    """
    files = self.AffectedSourceFiles(source_file_filter)
    return _RightHandSideLinesImpl(files)

  def ReadFile(self, file_item, mode='r'):
    """Reads an arbitrary file.

    Deny reading anything outside the repository.
    """
    if isinstance(file_item, AffectedFile):
      file_item = file_item.AbsoluteLocalPath()
    if not file_item.startswith(self.change.RepositoryRoot()):
      raise IOError('Access outside the repository root is denied.')
    return gclient_utils.FileRead(file_item, mode)

  @property
  def tbr(self):
    """Returns if a change is TBR'ed."""
    return 'TBR' in self.change.tags

  def RunTests(self, tests_mix, parallel=True):
    tests = []
    msgs = []
    for t in tests_mix:
      if isinstance(t, OutputApi.PresubmitResult):
        msgs.append(t)
      else:
        assert issubclass(t.message, _PresubmitResult)
        tests.append(t)
        if self.verbose:
          t.info = _PresubmitNotifyResult
    if len(tests) > 1 and parallel:
      # async recipe works around multiprocessing bug handling Ctrl-C
      msgs.extend(self._run_tests_pool.map_async(CallCommand, tests).get(99999))
    else:
      msgs.extend(map(CallCommand, tests))
    return [m for m in msgs if m]


class _DiffCache(object):
  """Caches diffs retrieved from a particular SCM."""
  def __init__(self, upstream=None):
    """Stores the upstream revision against which all diffs will be computed."""
    self._upstream = upstream

  def GetDiff(self, path, local_root):
    """Get the diff for a particular path."""
    raise NotImplementedError()


class _SvnDiffCache(_DiffCache):
  """DiffCache implementation for subversion."""
  def __init__(self, *args, **kwargs):
    super(_SvnDiffCache, self).__init__(*args, **kwargs)
    self._diffs_by_file = {}

  def GetDiff(self, path, local_root):
    if path not in self._diffs_by_file:
      self._diffs_by_file[path] = scm.SVN.GenerateDiff([path], local_root,
                                                       False, None)
    return self._diffs_by_file[path]


class _GitDiffCache(_DiffCache):
  """DiffCache implementation for git; gets all file diffs at once."""
  def __init__(self, upstream):
    super(_GitDiffCache, self).__init__(upstream=upstream)
    self._diffs_by_file = None

  def GetDiff(self, path, local_root):
    if not self._diffs_by_file:
      # Compute a single diff for all files and parse the output; should
      # with git this is much faster than computing one diff for each file.
      diffs = {}

      # Don't specify any filenames below, because there are command line length
      # limits on some platforms and GenerateDiff would fail.
      unified_diff = scm.GIT.GenerateDiff(local_root, files=[], full_move=True,
                                          branch=self._upstream)

      # This regex matches the path twice, separated by a space. Note that
      # filename itself may contain spaces.
      file_marker = re.compile('^diff --git (?P<filename>.*) (?P=filename)$')
      current_diff = []
      keep_line_endings = True
      for x in unified_diff.splitlines(keep_line_endings):
        match = file_marker.match(x)
        if match:
          # Marks the start of a new per-file section.
          diffs[match.group('filename')] = current_diff = [x]
        elif x.startswith('diff --git'):
          raise PresubmitFailure('Unexpected diff line: %s' % x)
        else:
          current_diff.append(x)

      self._diffs_by_file = dict(
        (normpath(path), ''.join(diff)) for path, diff in diffs.items())

    if path not in self._diffs_by_file:
      raise PresubmitFailure(
          'Unified diff did not contain entry for file %s' % path)

    return self._diffs_by_file[path]


class AffectedFile(object):
  """Representation of a file in a change."""

  DIFF_CACHE = _DiffCache

  # Method could be a function
  # pylint: disable=R0201
  def __init__(self, path, action, repository_root, diff_cache):
    self._path = path
    self._action = action
    self._local_root = repository_root
    self._is_directory = None
    self._properties = {}
    self._cached_changed_contents = None
    self._cached_new_contents = None
    self._diff_cache = diff_cache
    logging.debug('%s(%s)' % (self.__class__.__name__, self._path))

  def ServerPath(self):
    """Returns a path string that identifies the file in the SCM system.

    Returns the empty string if the file does not exist in SCM.
    """
    return ''

  def LocalPath(self):
    """Returns the path of this file on the local disk relative to client root.
    """
    return normpath(self._path)

  def AbsoluteLocalPath(self):
    """Returns the absolute path of this file on the local disk.
    """
    return os.path.abspath(os.path.join(self._local_root, self.LocalPath()))

  def IsDirectory(self):
    """Returns true if this object is a directory."""
    if self._is_directory is None:
      path = self.AbsoluteLocalPath()
      self._is_directory = (os.path.exists(path) and
                            os.path.isdir(path))
    return self._is_directory

  def Action(self):
    """Returns the action on this opened file, e.g. A, M, D, etc."""
    # TODO(maruel): Somewhat crappy, Could be "A" or "A  +" for svn but
    # different for other SCM.
    return self._action

  def Property(self, property_name):
    """Returns the specified SCM property of this file, or None if no such
    property.
    """
    return self._properties.get(property_name, None)

  def IsTextFile(self):
    """Returns True if the file is a text file and not a binary file.

    Deleted files are not text file."""
    raise NotImplementedError()  # Implement when needed

  def NewContents(self):
    """Returns an iterator over the lines in the new version of file.

    The new version is the file in the user's workspace, i.e. the "right hand
    side".

    Contents will be empty if the file is a directory or does not exist.
    Note: The carriage returns (LF or CR) are stripped off.
    """
    if self._cached_new_contents is None:
      self._cached_new_contents = []
      if not self.IsDirectory():
        try:
          self._cached_new_contents = gclient_utils.FileRead(
              self.AbsoluteLocalPath(), 'rU').splitlines()
        except IOError:
          pass  # File not found?  That's fine; maybe it was deleted.
    return self._cached_new_contents[:]

  def ChangedContents(self):
    """Returns a list of tuples (line number, line text) of all new lines.

     This relies on the scm diff output describing each changed code section
     with a line of the form

     ^@@ <old line num>,<old size> <new line num>,<new size> @@$
    """
    if self._cached_changed_contents is not None:
      return self._cached_changed_contents[:]
    self._cached_changed_contents = []
    line_num = 0

    if self.IsDirectory():
      return []

    for line in self.GenerateScmDiff().splitlines():
      m = re.match(r'^@@ [0-9\,\+\-]+ \+([0-9]+)\,[0-9]+ @@', line)
      if m:
        line_num = int(m.groups(1)[0])
        continue
      if line.startswith('+') and not line.startswith('++'):
        self._cached_changed_contents.append((line_num, line[1:]))
      if not line.startswith('-'):
        line_num += 1
    return self._cached_changed_contents[:]

  def __str__(self):
    return self.LocalPath()

  def GenerateScmDiff(self):
    return self._diff_cache.GetDiff(self.LocalPath(), self._local_root)


class SvnAffectedFile(AffectedFile):
  """Representation of a file in a change out of a Subversion checkout."""
  # Method 'NNN' is abstract in class 'NNN' but is not overridden
  # pylint: disable=W0223

  DIFF_CACHE = _SvnDiffCache

  def __init__(self, *args, **kwargs):
    AffectedFile.__init__(self, *args, **kwargs)
    self._server_path = None
    self._is_text_file = None

  def ServerPath(self):
    if self._server_path is None:
      self._server_path = scm.SVN.CaptureLocalInfo(
          [self.LocalPath()], self._local_root).get('URL', '')
    return self._server_path

  def IsDirectory(self):
    if self._is_directory is None:
      path = self.AbsoluteLocalPath()
      if os.path.exists(path):
        # Retrieve directly from the file system; it is much faster than
        # querying subversion, especially on Windows.
        self._is_directory = os.path.isdir(path)
      else:
        self._is_directory = scm.SVN.CaptureLocalInfo(
            [self.LocalPath()], self._local_root
            ).get('Node Kind') in ('dir', 'directory')
    return self._is_directory

  def Property(self, property_name):
    if not property_name in self._properties:
      self._properties[property_name] = scm.SVN.GetFileProperty(
          self.LocalPath(), property_name, self._local_root).rstrip()
    return self._properties[property_name]

  def IsTextFile(self):
    if self._is_text_file is None:
      if self.Action() == 'D':
        # A deleted file is not a text file.
        self._is_text_file = False
      elif self.IsDirectory():
        self._is_text_file = False
      else:
        mime_type = scm.SVN.GetFileProperty(
            self.LocalPath(), 'svn:mime-type', self._local_root)
        self._is_text_file = (not mime_type or mime_type.startswith('text/'))
    return self._is_text_file


class GitAffectedFile(AffectedFile):
  """Representation of a file in a change out of a git checkout."""
  # Method 'NNN' is abstract in class 'NNN' but is not overridden
  # pylint: disable=W0223

  DIFF_CACHE = _GitDiffCache

  def __init__(self, *args, **kwargs):
    AffectedFile.__init__(self, *args, **kwargs)
    self._server_path = None
    self._is_text_file = None

  def ServerPath(self):
    if self._server_path is None:
      raise NotImplementedError('TODO(maruel) Implement.')
    return self._server_path

  def IsDirectory(self):
    if self._is_directory is None:
      path = self.AbsoluteLocalPath()
      if os.path.exists(path):
        # Retrieve directly from the file system; it is much faster than
        # querying subversion, especially on Windows.
        self._is_directory = os.path.isdir(path)
      else:
        self._is_directory = False
    return self._is_directory

  def Property(self, property_name):
    if not property_name in self._properties:
      raise NotImplementedError('TODO(maruel) Implement.')
    return self._properties[property_name]

  def IsTextFile(self):
    if self._is_text_file is None:
      if self.Action() == 'D':
        # A deleted file is not a text file.
        self._is_text_file = False
      elif self.IsDirectory():
        self._is_text_file = False
      else:
        self._is_text_file = os.path.isfile(self.AbsoluteLocalPath())
    return self._is_text_file


class Change(object):
  """Describe a change.

  Used directly by the presubmit scripts to query the current change being
  tested.

  Instance members:
    tags: Dictionary of KEY=VALUE pairs found in the change description.
    self.KEY: equivalent to tags['KEY']
  """

  _AFFECTED_FILES = AffectedFile

  # Matches key/value (or "tag") lines in changelist descriptions.
  TAG_LINE_RE = re.compile(
      '^[ \t]*(?P<key>[A-Z][A-Z_0-9]*)[ \t]*=[ \t]*(?P<value>.*?)[ \t]*$')
  scm = ''

  def __init__(
      self, name, description, local_root, files, issue, patchset, author,
      upstream=None):
    if files is None:
      files = []
    self._name = name
    # Convert root into an absolute path.
    self._local_root = os.path.abspath(local_root)
    self._upstream = upstream
    self.issue = issue
    self.patchset = patchset
    self.author_email = author

    self._full_description = ''
    self.tags = {}
    self._description_without_tags = ''
    self.SetDescriptionText(description)

    assert all(
        (isinstance(f, (list, tuple)) and len(f) == 2) for f in files), files

    diff_cache = self._AFFECTED_FILES.DIFF_CACHE(self._upstream)
    self._affected_files = [
        self._AFFECTED_FILES(path, action.strip(), self._local_root, diff_cache)
        for action, path in files
    ]

  def Name(self):
    """Returns the change name."""
    return self._name

  def DescriptionText(self):
    """Returns the user-entered changelist description, minus tags.

    Any line in the user-provided description starting with e.g. "FOO="
    (whitespace permitted before and around) is considered a tag line.  Such
    lines are stripped out of the description this function returns.
    """
    return self._description_without_tags

  def FullDescriptionText(self):
    """Returns the complete changelist description including tags."""
    return self._full_description

  def SetDescriptionText(self, description):
    """Sets the full description text (including tags) to |description|.

    Also updates the list of tags."""
    self._full_description = description

    # From the description text, build up a dictionary of key/value pairs
    # plus the description minus all key/value or "tag" lines.
    description_without_tags = []
    self.tags = {}
    for line in self._full_description.splitlines():
      m = self.TAG_LINE_RE.match(line)
      if m:
        self.tags[m.group('key')] = m.group('value')
      else:
        description_without_tags.append(line)

    # Change back to text and remove whitespace at end.
    self._description_without_tags = (
        '\n'.join(description_without_tags).rstrip())

  def RepositoryRoot(self):
    """Returns the repository (checkout) root directory for this change,
    as an absolute path.
    """
    return self._local_root

  def __getattr__(self, attr):
    """Return tags directly as attributes on the object."""
    if not re.match(r"^[A-Z_]*$", attr):
      raise AttributeError(self, attr)
    return self.tags.get(attr)

  def AllFiles(self, root=None):
    """List all files under source control in the repo."""
    raise NotImplementedError()

  def AffectedFiles(self, include_dirs=False, include_deletes=True,
                    file_filter=None):
    """Returns a list of AffectedFile instances for all files in the change.

    Args:
      include_deletes: If false, deleted files will be filtered out.
      include_dirs: True to include directories in the list
      file_filter: An additional filter to apply.

    Returns:
      [AffectedFile(path, action), AffectedFile(path, action)]
    """
    if include_dirs:
      affected = self._affected_files
    else:
      affected = filter(lambda x: not x.IsDirectory(), self._affected_files)

    affected = filter(file_filter, affected)

    if include_deletes:
      return affected
    else:
      return filter(lambda x: x.Action() != 'D', affected)

  def AffectedTextFiles(self, include_deletes=None):
    """Return a list of the existing text files in a change."""
    if include_deletes is not None:
      warn("AffectedTextFiles(include_deletes=%s)"
               " is deprecated and ignored" % str(include_deletes),
           category=DeprecationWarning,
           stacklevel=2)
    return filter(lambda x: x.IsTextFile(),
                  self.AffectedFiles(include_dirs=False, include_deletes=False))

  def LocalPaths(self, include_dirs=False):
    """Convenience function."""
    return [af.LocalPath() for af in self.AffectedFiles(include_dirs)]

  def AbsoluteLocalPaths(self, include_dirs=False):
    """Convenience function."""
    return [af.AbsoluteLocalPath() for af in self.AffectedFiles(include_dirs)]

  def ServerPaths(self, include_dirs=False):
    """Convenience function."""
    return [af.ServerPath() for af in self.AffectedFiles(include_dirs)]

  def RightHandSideLines(self):
    """An iterator over all text lines in "new" version of changed files.

    Lists lines from new or modified text files in the change.

    This is useful for doing line-by-line regex checks, like checking for
    trailing whitespace.

    Yields:
      a 3 tuple:
        the AffectedFile instance of the current file;
        integer line number (1-based); and
        the contents of the line as a string.
    """
    return _RightHandSideLinesImpl(
        x for x in self.AffectedFiles(include_deletes=False)
        if x.IsTextFile())


class SvnChange(Change):
  _AFFECTED_FILES = SvnAffectedFile
  scm = 'svn'
  _changelists = None

  def _GetChangeLists(self):
    """Get all change lists."""
    if self._changelists == None:
      previous_cwd = os.getcwd()
      os.chdir(self.RepositoryRoot())
      # Need to import here to avoid circular dependency.
      import gcl
      self._changelists = gcl.GetModifiedFiles()
      os.chdir(previous_cwd)
    return self._changelists

  def GetAllModifiedFiles(self):
    """Get all modified files."""
    changelists = self._GetChangeLists()
    all_modified_files = []
    for cl in changelists.values():
      all_modified_files.extend(
          [os.path.join(self.RepositoryRoot(), f[1]) for f in cl])
    return all_modified_files

  def GetModifiedFiles(self):
    """Get modified files in the current CL."""
    changelists = self._GetChangeLists()
    return [os.path.join(self.RepositoryRoot(), f[1])
            for f in changelists[self.Name()]]

  def AllFiles(self, root=None):
    """List all files under source control in the repo."""
    root = root or self.RepositoryRoot()
    return subprocess.check_output(
        ['svn', 'ls', '-R', '.'], cwd=root).splitlines()


class GitChange(Change):
  _AFFECTED_FILES = GitAffectedFile
  scm = 'git'

  def AllFiles(self, root=None):
    """List all files under source control in the repo."""
    root = root or self.RepositoryRoot()
    return subprocess.check_output(
        ['git', 'ls-files', '--', '.'], cwd=root).splitlines()


def ListRelevantPresubmitFiles(files, root):
  """Finds all presubmit files that apply to a given set of source files.

  If inherit-review-settings-ok is present right under root, looks for
  PRESUBMIT.py in directories enclosing root.

  Args:
    files: An iterable container containing file paths.
    root: Path where to stop searching.

  Return:
    List of absolute paths of the existing PRESUBMIT.py scripts.
  """
  files = [normpath(os.path.join(root, f)) for f in files]

  # List all the individual directories containing files.
  directories = set([os.path.dirname(f) for f in files])

  # Ignore root if inherit-review-settings-ok is present.
  if os.path.isfile(os.path.join(root, 'inherit-review-settings-ok')):
    root = None

  # Collect all unique directories that may contain PRESUBMIT.py.
  candidates = set()
  for directory in directories:
    while True:
      if directory in candidates:
        break
      candidates.add(directory)
      if directory == root:
        break
      parent_dir = os.path.dirname(directory)
      if parent_dir == directory:
        # We hit the system root directory.
        break
      directory = parent_dir

  # Look for PRESUBMIT.py in all candidate directories.
  results = []
  for directory in sorted(list(candidates)):
    p = os.path.join(directory, 'PRESUBMIT.py')
    if os.path.isfile(p):
      results.append(p)

  logging.debug('Presubmit files: %s' % ','.join(results))
  return results


class GetTrySlavesExecuter(object):
  @staticmethod
  def ExecPresubmitScript(script_text, presubmit_path, project, change):
    """Executes GetPreferredTrySlaves() from a single presubmit script.

    This will soon be deprecated and replaced by GetPreferredTryMasters().

    Args:
      script_text: The text of the presubmit script.
      presubmit_path: Project script to run.
      project: Project name to pass to presubmit script for bot selection.

    Return:
      A list of try slaves.
    """
    context = {}
    main_path = os.getcwd()
    try:
      os.chdir(os.path.dirname(presubmit_path))
      exec script_text in context
    except Exception, e:
      raise PresubmitFailure('"%s" had an exception.\n%s' % (presubmit_path, e))
    finally:
      os.chdir(main_path)

    function_name = 'GetPreferredTrySlaves'
    if function_name in context:
      get_preferred_try_slaves = context[function_name]
      function_info = inspect.getargspec(get_preferred_try_slaves)
      if len(function_info[0]) == 1:
        result = get_preferred_try_slaves(project)
      elif len(function_info[0]) == 2:
        result = get_preferred_try_slaves(project, change)
      else:
        result = get_preferred_try_slaves()
      if not isinstance(result, types.ListType):
        raise PresubmitFailure(
            'Presubmit functions must return a list, got a %s instead: %s' %
            (type(result), str(result)))
      for item in result:
        if isinstance(item, basestring):
          # Old-style ['bot'] format.
          botname = item
        elif isinstance(item, tuple):
          # New-style [('bot', set(['tests']))] format.
          botname = item[0]
        else:
          raise PresubmitFailure('PRESUBMIT.py returned invalid tryslave/test'
                                 ' format.')

        if botname != botname.strip():
          raise PresubmitFailure(
              'Try slave names cannot start/end with whitespace')
        if ',' in botname:
          raise PresubmitFailure(
              'Do not use \',\' separated builder or test names: %s' % botname)
    else:
      result = []

    def valid_oldstyle(result):
      return all(isinstance(i, basestring) for i in result)

    def valid_newstyle(result):
      return (all(isinstance(i, tuple) for i in result) and
              all(len(i) == 2 for i in result) and
              all(isinstance(i[0], basestring) for i in result) and
              all(isinstance(i[1], set) for i in result)
             )

    # Ensure it's either all old-style or all new-style.
    if not valid_oldstyle(result) and not valid_newstyle(result):
      raise PresubmitFailure(
          'PRESUBMIT.py returned invalid trybot specification!')

    return result


class GetTryMastersExecuter(object):
  @staticmethod
  def ExecPresubmitScript(script_text, presubmit_path, project, change):
    """Executes GetPreferredTryMasters() from a single presubmit script.

    Args:
      script_text: The text of the presubmit script.
      presubmit_path: Project script to run.
      project: Project name to pass to presubmit script for bot selection.

    Return:
      A map of try masters to map of builders to set of tests.
    """
    context = {}
    try:
      exec script_text in context
    except Exception, e:
      raise PresubmitFailure('"%s" had an exception.\n%s'
                             % (presubmit_path, e))

    function_name = 'GetPreferredTryMasters'
    if function_name not in context:
      return {}
    get_preferred_try_masters = context[function_name]
    if not len(inspect.getargspec(get_preferred_try_masters)[0]) == 2:
      raise PresubmitFailure(
          'Expected function "GetPreferredTryMasters" to take two arguments.')
    return get_preferred_try_masters(project, change)


class GetPostUploadExecuter(object):
  @staticmethod
  def ExecPresubmitScript(script_text, presubmit_path, cl, change):
    """Executes PostUploadHook() from a single presubmit script.

    Args:
      script_text: The text of the presubmit script.
      presubmit_path: Project script to run.
      cl: The Changelist object.
      change: The Change object.

    Return:
      A list of results objects.
    """
    context = {}
    try:
      exec script_text in context
    except Exception, e:
      raise PresubmitFailure('"%s" had an exception.\n%s'
                             % (presubmit_path, e))

    function_name = 'PostUploadHook'
    if function_name not in context:
      return {}
    post_upload_hook = context[function_name]
    if not len(inspect.getargspec(post_upload_hook)[0]) == 3:
      raise PresubmitFailure(
          'Expected function "PostUploadHook" to take three arguments.')
    return post_upload_hook(cl, change, OutputApi(False))


def DoGetTrySlaves(change,
                   changed_files,
                   repository_root,
                   default_presubmit,
                   project,
                   verbose,
                   output_stream):
  """Get the list of try servers from the presubmit scripts (deprecated).

  Args:
    changed_files: List of modified files.
    repository_root: The repository root.
    default_presubmit: A default presubmit script to execute in any case.
    project: Optional name of a project used in selecting trybots.
    verbose: Prints debug info.
    output_stream: A stream to write debug output to.

  Return:
    List of try slaves
  """
  presubmit_files = ListRelevantPresubmitFiles(changed_files, repository_root)
  if not presubmit_files and verbose:
    output_stream.write("Warning, no PRESUBMIT.py found.\n")
  results = []
  executer = GetTrySlavesExecuter()

  if default_presubmit:
    if verbose:
      output_stream.write("Running default presubmit script.\n")
    fake_path = os.path.join(repository_root, 'PRESUBMIT.py')
    results.extend(executer.ExecPresubmitScript(
        default_presubmit, fake_path, project, change))
  for filename in presubmit_files:
    filename = os.path.abspath(filename)
    if verbose:
      output_stream.write("Running %s\n" % filename)
    # Accept CRLF presubmit script.
    presubmit_script = gclient_utils.FileRead(filename, 'rU')
    results.extend(executer.ExecPresubmitScript(
        presubmit_script, filename, project, change))


  slave_dict = {}
  old_style = filter(lambda x: isinstance(x, basestring), results)
  new_style = filter(lambda x: isinstance(x, tuple), results)

  for result in new_style:
    slave_dict.setdefault(result[0], set()).update(result[1])
  slaves = list(slave_dict.items())

  slaves.extend(set(old_style))

  if slaves and verbose:
    output_stream.write(', '.join((str(x) for x in slaves)))
    output_stream.write('\n')
  return slaves


def _MergeMasters(masters1, masters2):
  """Merges two master maps. Merges also the tests of each builder."""
  result = {}
  for (master, builders) in itertools.chain(masters1.iteritems(),
                                            masters2.iteritems()):
    new_builders = result.setdefault(master, {})
    for (builder, tests) in builders.iteritems():
      new_builders.setdefault(builder, set([])).update(tests)
  return result


def DoGetTryMasters(change,
                    changed_files,
                    repository_root,
                    default_presubmit,
                    project,
                    verbose,
                    output_stream):
  """Get the list of try masters from the presubmit scripts.

  Args:
    changed_files: List of modified files.
    repository_root: The repository root.
    default_presubmit: A default presubmit script to execute in any case.
    project: Optional name of a project used in selecting trybots.
    verbose: Prints debug info.
    output_stream: A stream to write debug output to.

  Return:
    Map of try masters to map of builders to set of tests.
  """
  presubmit_files = ListRelevantPresubmitFiles(changed_files, repository_root)
  if not presubmit_files and verbose:
    output_stream.write("Warning, no PRESUBMIT.py found.\n")
  results = {}
  executer = GetTryMastersExecuter()

  if default_presubmit:
    if verbose:
      output_stream.write("Running default presubmit script.\n")
    fake_path = os.path.join(repository_root, 'PRESUBMIT.py')
    results = _MergeMasters(results, executer.ExecPresubmitScript(
        default_presubmit, fake_path, project, change))
  for filename in presubmit_files:
    filename = os.path.abspath(filename)
    if verbose:
      output_stream.write("Running %s\n" % filename)
    # Accept CRLF presubmit script.
    presubmit_script = gclient_utils.FileRead(filename, 'rU')
    results = _MergeMasters(results, executer.ExecPresubmitScript(
        presubmit_script, filename, project, change))

  # Make sets to lists again for later JSON serialization.
  for builders in results.itervalues():
    for builder in builders:
      builders[builder] = list(builders[builder])

  if results and verbose:
    output_stream.write('%s\n' % str(results))
  return results


def DoPostUploadExecuter(change,
                         cl,
                         repository_root,
                         verbose,
                         output_stream):
  """Execute the post upload hook.

  Args:
    change: The Change object.
    cl: The Changelist object.
    repository_root: The repository root.
    verbose: Prints debug info.
    output_stream: A stream to write debug output to.
  """
  presubmit_files = ListRelevantPresubmitFiles(
      change.LocalPaths(), repository_root)
  if not presubmit_files and verbose:
    output_stream.write("Warning, no PRESUBMIT.py found.\n")
  results = []
  executer = GetPostUploadExecuter()
  # The root presubmit file should be executed after the ones in subdirectories.
  # i.e. the specific post upload hooks should run before the general ones.
  # Thus, reverse the order provided by ListRelevantPresubmitFiles.
  presubmit_files.reverse()

  for filename in presubmit_files:
    filename = os.path.abspath(filename)
    if verbose:
      output_stream.write("Running %s\n" % filename)
    # Accept CRLF presubmit script.
    presubmit_script = gclient_utils.FileRead(filename, 'rU')
    results.extend(executer.ExecPresubmitScript(
        presubmit_script, filename, cl, change))
  output_stream.write('\n')
  if results:
    output_stream.write('** Post Upload Hook Messages **\n')
  for result in results:
    result.handle(output_stream)
    output_stream.write('\n')

  return results


class PresubmitExecuter(object):
  def __init__(self, change, committing, rietveld_obj, verbose,
               gerrit_obj=None, dry_run=None):
    """
    Args:
      change: The Change object.
      committing: True if 'gcl commit' is running, False if 'gcl upload' is.
      rietveld_obj: rietveld.Rietveld client object.
      gerrit_obj: provides basic Gerrit codereview functionality.
      dry_run: if true, some Checks will be skipped.
    """
    self.change = change
    self.committing = committing
    self.rietveld = rietveld_obj
    self.gerrit = gerrit_obj
    self.verbose = verbose
    self.dry_run = dry_run

  def ExecPresubmitScript(self, script_text, presubmit_path):
    """Executes a single presubmit script.

    Args:
      script_text: The text of the presubmit script.
      presubmit_path: The path to the presubmit file (this will be reported via
        input_api.PresubmitLocalPath()).

    Return:
      A list of result objects, empty if no problems.
    """

    # Change to the presubmit file's directory to support local imports.
    main_path = os.getcwd()
    os.chdir(os.path.dirname(presubmit_path))

    # Load the presubmit script into context.
    input_api = InputApi(self.change, presubmit_path, self.committing,
                         self.rietveld, self.verbose,
                         gerrit_obj=self.gerrit, dry_run=self.dry_run)
    context = {}
    try:
      exec script_text in context
    except Exception, e:
      raise PresubmitFailure('"%s" had an exception.\n%s' % (presubmit_path, e))

    # These function names must change if we make substantial changes to
    # the presubmit API that are not backwards compatible.
    if self.committing:
      function_name = 'CheckChangeOnCommit'
    else:
      function_name = 'CheckChangeOnUpload'
    if function_name in context:
      context['__args'] = (input_api, OutputApi(self.committing))
      logging.debug('Running %s in %s' % (function_name, presubmit_path))
      result = eval(function_name + '(*__args)', context)
      logging.debug('Running %s done.' % function_name)
      if not (isinstance(result, types.TupleType) or
              isinstance(result, types.ListType)):
        raise PresubmitFailure(
          'Presubmit functions must return a tuple or list')
      for item in result:
        if not isinstance(item, OutputApi.PresubmitResult):
          raise PresubmitFailure(
            'All presubmit results must be of types derived from '
            'output_api.PresubmitResult')
    else:
      result = ()  # no error since the script doesn't care about current event.

    # Return the process to the original working directory.
    os.chdir(main_path)
    return result


def DoPresubmitChecks(change,
                      committing,
                      verbose,
                      output_stream,
                      input_stream,
                      default_presubmit,
                      may_prompt,
                      rietveld_obj,
                      gerrit_obj=None,
                      dry_run=None):
  """Runs all presubmit checks that apply to the files in the change.

  This finds all PRESUBMIT.py files in directories enclosing the files in the
  change (up to the repository root) and calls the relevant entrypoint function
  depending on whether the change is being committed or uploaded.

  Prints errors, warnings and notifications.  Prompts the user for warnings
  when needed.

  Args:
    change: The Change object.
    committing: True if 'gcl commit' is running, False if 'gcl upload' is.
    verbose: Prints debug info.
    output_stream: A stream to write output from presubmit tests to.
    input_stream: A stream to read input from the user.
    default_presubmit: A default presubmit script to execute in any case.
    may_prompt: Enable (y/n) questions on warning or error.
    rietveld_obj: rietveld.Rietveld object.
    gerrit_obj: provides basic Gerrit codereview functionality.
    dry_run: if true, some Checks will be skipped.

  Warning:
    If may_prompt is true, output_stream SHOULD be sys.stdout and input_stream
    SHOULD be sys.stdin.

  Return:
    A PresubmitOutput object. Use output.should_continue() to figure out
    if there were errors or warnings and the caller should abort.
  """
  old_environ = os.environ
  try:
    # Make sure python subprocesses won't generate .pyc files.
    os.environ = os.environ.copy()
    os.environ['PYTHONDONTWRITEBYTECODE'] = '1'

    output = PresubmitOutput(input_stream, output_stream)
    if committing:
      output.write("Running presubmit commit checks ...\n")
    else:
      output.write("Running presubmit upload checks ...\n")
    start_time = time.time()
    presubmit_files = ListRelevantPresubmitFiles(
        change.AbsoluteLocalPaths(True), change.RepositoryRoot())
    if not presubmit_files and verbose:
      output.write("Warning, no PRESUBMIT.py found.\n")
    results = []
    executer = PresubmitExecuter(change, committing, rietveld_obj, verbose,
                                 gerrit_obj, dry_run)
    if default_presubmit:
      if verbose:
        output.write("Running default presubmit script.\n")
      fake_path = os.path.join(change.RepositoryRoot(), 'PRESUBMIT.py')
      results += executer.ExecPresubmitScript(default_presubmit, fake_path)
    for filename in presubmit_files:
      filename = os.path.abspath(filename)
      if verbose:
        output.write("Running %s\n" % filename)
      # Accept CRLF presubmit script.
      presubmit_script = gclient_utils.FileRead(filename, 'rU')
      results += executer.ExecPresubmitScript(presubmit_script, filename)

    errors = []
    notifications = []
    warnings = []
    for result in results:
      if result.fatal:
        errors.append(result)
      elif result.should_prompt:
        warnings.append(result)
      else:
        notifications.append(result)

    output.write('\n')
    for name, items in (('Messages', notifications),
                        ('Warnings', warnings),
                        ('ERRORS', errors)):
      if items:
        output.write('** Presubmit %s **\n' % name)
        for item in items:
          item.handle(output)
          output.write('\n')

    total_time = time.time() - start_time
    if total_time > 1.0:
      output.write("Presubmit checks took %.1fs to calculate.\n\n" % total_time)

    if not errors:
      if not warnings:
        output.write('Presubmit checks passed.\n')
      elif may_prompt:
        output.prompt_yes_no('There were presubmit warnings. '
                            'Are you sure you wish to continue? (y/N): ')
      else:
        output.fail()

    global _ASKED_FOR_FEEDBACK
    # Ask for feedback one time out of 5.
    if (len(results) and random.randint(0, 4) == 0 and not _ASKED_FOR_FEEDBACK):
      output.write(
          'Was the presubmit check useful? If not, run "git cl presubmit -v"\n'
          'to figure out which PRESUBMIT.py was run, then run git blame\n'
          'on the file to figure out who to ask for help.\n')
      _ASKED_FOR_FEEDBACK = True
    return output
  finally:
    os.environ = old_environ


def ScanSubDirs(mask, recursive):
  if not recursive:
    return [x for x in glob.glob(mask) if x not in ('.svn', '.git')]
  else:
    results = []
    for root, dirs, files in os.walk('.'):
      if '.svn' in dirs:
        dirs.remove('.svn')
      if '.git' in dirs:
        dirs.remove('.git')
      for name in files:
        if fnmatch.fnmatch(name, mask):
          results.append(os.path.join(root, name))
    return results


def ParseFiles(args, recursive):
  logging.debug('Searching for %s' % args)
  files = []
  for arg in args:
    files.extend([('M', f) for f in ScanSubDirs(arg, recursive)])
  return files


def load_files(options, args):
  """Tries to determine the SCM."""
  change_scm = scm.determine_scm(options.root)
  files = []
  if args:
    files = ParseFiles(args, options.recursive)
  if change_scm == 'svn':
    change_class = SvnChange
    if not files:
      files = scm.SVN.CaptureStatus([], options.root)
  elif change_scm == 'git':
    change_class = GitChange
    upstream = options.upstream or None
    if not files:
      files = scm.GIT.CaptureStatus([], options.root, upstream)
  else:
    logging.info('Doesn\'t seem under source control. Got %d files' % len(args))
    if not files:
      return None, None
    change_class = Change
  return change_class, files


class NonexistantCannedCheckFilter(Exception):
  pass


@contextlib.contextmanager
def canned_check_filter(method_names):
  filtered = {}
  try:
    for method_name in method_names:
      if not hasattr(presubmit_canned_checks, method_name):
        raise NonexistantCannedCheckFilter(method_name)
      filtered[method_name] = getattr(presubmit_canned_checks, method_name)
      setattr(presubmit_canned_checks, method_name, lambda *_a, **_kw: [])
    yield
  finally:
    for name, method in filtered.iteritems():
      setattr(presubmit_canned_checks, name, method)


def CallCommand(cmd_data):
  """Runs an external program, potentially from a child process created by the
  multiprocessing module.

  multiprocessing needs a top level function with a single argument.
  """
  cmd_data.kwargs['stdout'] = subprocess.PIPE
  cmd_data.kwargs['stderr'] = subprocess.STDOUT
  try:
    start = time.time()
    (out, _), code = subprocess.communicate(cmd_data.cmd, **cmd_data.kwargs)
    duration = time.time() - start
  except OSError as e:
    duration = time.time() - start
    return cmd_data.message(
        '%s exec failure (%4.2fs)\n   %s' % (cmd_data.name, duration, e))
  if code != 0:
    return cmd_data.message(
        '%s (%4.2fs) failed\n%s' % (cmd_data.name, duration, out))
  if cmd_data.info:
    return cmd_data.info('%s (%4.2fs)' % (cmd_data.name, duration))


def main(argv=None):
  parser = optparse.OptionParser(usage="%prog [options] <files...>",
                                 version="%prog " + str(__version__))
  parser.add_option("-c", "--commit", action="store_true", default=False,
                   help="Use commit instead of upload checks")
  parser.add_option("-u", "--upload", action="store_false", dest='commit',
                   help="Use upload instead of commit checks")
  parser.add_option("-r", "--recursive", action="store_true",
                   help="Act recursively")
  parser.add_option("-v", "--verbose", action="count", default=0,
                   help="Use 2 times for more debug info")
  parser.add_option("--name", default='no name')
  parser.add_option("--author")
  parser.add_option("--description", default='')
  parser.add_option("--issue", type='int', default=0)
  parser.add_option("--patchset", type='int', default=0)
  parser.add_option("--root", default=os.getcwd(),
                    help="Search for PRESUBMIT.py up to this directory. "
                    "If inherit-review-settings-ok is present in this "
                    "directory, parent directories up to the root file "
                    "system directories will also be searched.")
  parser.add_option("--upstream",
                    help="Git only: the base ref or upstream branch against "
                    "which the diff should be computed.")
  parser.add_option("--default_presubmit")
  parser.add_option("--may_prompt", action='store_true', default=False)
  parser.add_option("--skip_canned", action='append', default=[],
                    help="A list of checks to skip which appear in "
                    "presubmit_canned_checks. Can be provided multiple times "
                    "to skip multiple canned checks.")
  parser.add_option("--dry_run", action='store_true',
                    help=optparse.SUPPRESS_HELP)
  parser.add_option("--gerrit_url", help=optparse.SUPPRESS_HELP)
  parser.add_option("--gerrit_fetch", action='store_true',
                    help=optparse.SUPPRESS_HELP)
  parser.add_option("--rietveld_url", help=optparse.SUPPRESS_HELP)
  parser.add_option("--rietveld_email", help=optparse.SUPPRESS_HELP)
  parser.add_option("--rietveld_fetch", action='store_true', default=False,
                    help=optparse.SUPPRESS_HELP)
  # These are for OAuth2 authentication for bots. See also apply_issue.py
  parser.add_option("--rietveld_email_file", help=optparse.SUPPRESS_HELP)
  parser.add_option("--rietveld_private_key_file", help=optparse.SUPPRESS_HELP)

  # TODO(phajdan.jr): Update callers and remove obsolete --trybot-json .
  parser.add_option("--trybot-json",
                    help="Output trybot information to the file specified.")
  auth.add_auth_options(parser)
  options, args = parser.parse_args(argv)
  auth_config = auth.extract_auth_config_from_options(options)

  if options.verbose >= 2:
    logging.basicConfig(level=logging.DEBUG)
  elif options.verbose:
    logging.basicConfig(level=logging.INFO)
  else:
    logging.basicConfig(level=logging.ERROR)

  if (any((options.rietveld_url, options.rietveld_email_file,
           options.rietveld_fetch, options.rietveld_private_key_file))
      and any((options.gerrit_url, options.gerrit_fetch))):
    parser.error('Options for only codereview --rietveld_* or --gerrit_* '
                 'allowed')

  if options.rietveld_email and options.rietveld_email_file:
    parser.error("Only one of --rietveld_email or --rietveld_email_file "
                 "can be passed to this program.")
  if options.rietveld_email_file:
    with open(options.rietveld_email_file, "rb") as f:
      options.rietveld_email = f.read().strip()

  change_class, files = load_files(options, args)
  if not change_class:
    parser.error('For unversioned directory, <files> is not optional.')
  logging.info('Found %d file(s).' % len(files))

  rietveld_obj, gerrit_obj = None, None

  if options.rietveld_url:
    # The empty password is permitted: '' is not None.
    if options.rietveld_private_key_file:
      rietveld_obj = rietveld.JwtOAuth2Rietveld(
        options.rietveld_url,
        options.rietveld_email,
        options.rietveld_private_key_file)
    else:
      rietveld_obj = rietveld.CachingRietveld(
        options.rietveld_url,
        auth_config,
        options.rietveld_email)
    if options.rietveld_fetch:
      assert options.issue
      props = rietveld_obj.get_issue_properties(options.issue, False)
      options.author = props['owner_email']
      options.description = props['description']
      logging.info('Got author: "%s"', options.author)
      logging.info('Got description: """\n%s\n"""', options.description)

  if options.gerrit_url and options.gerrit_fetch:
    assert options.issue and options.patchset
    rietveld_obj = None
    gerrit_obj = GerritAccessor(urlparse.urlparse(options.gerrit_url).netloc)
    options.author = gerrit_obj.GetChangeOwner(options.issue)
    options.description = gerrit_obj.GetChangeDescription(options.issue,
                                                          options.patchset)
    logging.info('Got author: "%s"', options.author)
    logging.info('Got description: """\n%s\n"""', options.description)

  try:
    with canned_check_filter(options.skip_canned):
      results = DoPresubmitChecks(
          change_class(options.name,
                       options.description,
                       options.root,
                       files,
                       options.issue,
                       options.patchset,
                       options.author,
                       upstream=options.upstream),
          options.commit,
          options.verbose,
          sys.stdout,
          sys.stdin,
          options.default_presubmit,
          options.may_prompt,
          rietveld_obj,
          gerrit_obj,
          options.dry_run)
    return not results.should_continue()
  except NonexistantCannedCheckFilter, e:
    print >> sys.stderr, (
      'Attempted to skip nonexistent canned presubmit check: %s' % e.message)
    return 2
  except PresubmitFailure, e:
    print >> sys.stderr, e
    print >> sys.stderr, 'Maybe your depot_tools is out of date?'
    print >> sys.stderr, 'If all fails, contact maruel@'
    return 2


if __name__ == '__main__':
  fix_encoding.fix_encoding()
  try:
    sys.exit(main())
  except KeyboardInterrupt:
    sys.stderr.write('interrupted\n')
    sys.exit(2)