split_cl.py

#!/usr/bin/env python3
# Copyright 2017 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.

"""Splits a branch into smaller branches and uploads CLs."""

from __future__ import print_function

import collections
import os
import re
import subprocess2
import sys
import tempfile

import gclient_utils
import git_footers
import scm

import git_common as git


# If a call to `git cl split` will generate more than this number of CLs, the
# command will prompt the user to make sure they know what they're doing. Large
# numbers of CLs generated by `git cl split` have caused infrastructure issues
# in the past.
CL_SPLIT_FORCE_LIMIT = 10

# The maximum number of top reviewers to list. `git cl split` may send many CLs
# to a single reviewer, so the top reviewers with the most CLs sent to them
# will be listed.
CL_SPLIT_TOP_REVIEWERS = 5

FilesAndOwnersDirectory = collections.namedtuple("FilesAndOwnersDirectory",
                                                 "files owners_directories")


def EnsureInGitRepository():
  """Throws an exception if the current directory is not a git repository."""
  git.run('rev-parse')


def CreateBranchForDirectories(prefix, directories, upstream):
  """Creates a branch named |prefix| + "_" + |directories[0]| + "_split".

  Return false if the branch already exists. |upstream| is used as upstream for
  the created branch.
  """
  existing_branches = set(git.branches(use_limit = False))
  branch_name = prefix + '_' + directories[0] + '_split'
  if branch_name in existing_branches:
    return False
  git.run('checkout', '-t', upstream, '-b', branch_name)
  return True


def FormatDirectoriesForPrinting(directories, prefix=None):
  """Formats directory list for printing

  Uses dedicated format for single-item list."""

  prefixed = directories
  if prefix:
    prefixed = [(prefix + d) for d in directories]

  return str(prefixed) if len(prefixed) > 1 else str(prefixed[0])


def FormatDescriptionOrComment(txt, directories):
  """Replaces $directory with |directories| in |txt|."""
  to_insert = FormatDirectoriesForPrinting(directories, prefix='/')
  return txt.replace('$directory', to_insert)


def AddUploadedByGitClSplitToDescription(description):
  """Adds a 'This CL was uploaded by git cl split.' line to |description|.

  The line is added before footers, or at the end of |description| if it has no
  footers.
  """
  split_footers = git_footers.split_footers(description)
  lines = split_footers[0]
  if lines[-1] and not lines[-1].isspace():
    lines = lines + ['']
  lines = lines + ['This CL was uploaded by git cl split.']
  if split_footers[1]:
    lines += [''] + split_footers[1]
  return '\n'.join(lines)


def UploadCl(refactor_branch, refactor_branch_upstream, directories, files,
             description, comment, reviewers, changelist, cmd_upload,
             cq_dry_run, enable_auto_submit, topic, repository_root):
  """Uploads a CL with all changes to |files| in |refactor_branch|.

  Args:
    refactor_branch: Name of the branch that contains the changes to upload.
    refactor_branch_upstream: Name of the upstream of |refactor_branch|.
    directories: Paths to the directories that contain the OWNERS files for
        which to upload a CL.
    files: List of AffectedFile instances to include in the uploaded CL.
    description: Description of the uploaded CL.
    comment: Comment to post on the uploaded CL.
    reviewers: A set of reviewers for the CL.
    changelist: The Changelist class.
    cmd_upload: The function associated with the git cl upload command.
    cq_dry_run: If CL uploads should also do a cq dry run.
    enable_auto_submit: If CL uploads should also enable auto submit.
    topic: Topic to associate with uploaded CLs.
  """
  # Create a branch.
  if not CreateBranchForDirectories(refactor_branch, directories,
                                    refactor_branch_upstream):
    print('Skipping ' + FormatDirectoriesForPrinting(directories) +
          ' for which a branch already exists.')
    return

  # Checkout all changes to files in |files|.
  deleted_files = []
  modified_files = []
  for action, f in files:
    abspath = os.path.abspath(os.path.join(repository_root, f))
    if action == 'D':
      deleted_files.append(abspath)
    else:
      modified_files.append(abspath)

  if deleted_files:
    git.run(*['rm'] + deleted_files)
  if modified_files:
    git.run(*['checkout', refactor_branch, '--'] + modified_files)

  # Commit changes. The temporary file is created with delete=False so that it
  # can be deleted manually after git has read it rather than automatically
  # when it is closed.
  with gclient_utils.temporary_file() as tmp_file:
    gclient_utils.FileWrite(
        tmp_file, FormatDescriptionOrComment(description, directories))
    git.run('commit', '-F', tmp_file)

  # Upload a CL.
  upload_args = ['-f']
  if reviewers:
    upload_args.extend(['-r', ','.join(sorted(reviewers))])
  if cq_dry_run:
    upload_args.append('--cq-dry-run')
  if not comment:
    upload_args.append('--send-mail')
  if enable_auto_submit:
    upload_args.append('--enable-auto-submit')
  if topic:
    upload_args.append('--topic={}'.format(topic))
  print('Uploading CL for ' + FormatDirectoriesForPrinting(directories) + '...')

  ret = cmd_upload(upload_args)
  if ret != 0:
    print('Uploading failed.')
    print('Note: git cl split has built-in resume capabilities.')
    print('Delete ' + git.current_branch() +
          ' then run git cl split again to resume uploading.')

  if comment:
    changelist().AddComment(FormatDescriptionOrComment(comment, directories),
                            publish=True)


def GetFilesSplitByOwners(files, max_depth):
  """Returns a map of files split by OWNERS file.

  Returns:
    A map where keys are paths to directories containing an OWNERS file and
    values are lists of files sharing an OWNERS file.
  """
  files_split_by_owners = {}
  for action, path in files:
    # normpath() is important to normalize separators here, in prepration for
    # str.split() before. It would be nicer to use something like pathlib here
    # but alas...
    dir_with_owners = os.path.normpath(os.path.dirname(path))
    if max_depth >= 1:
      dir_with_owners = os.path.join(
          *dir_with_owners.split(os.path.sep)[:max_depth])
    # Find the closest parent directory with an OWNERS file.
    while (dir_with_owners not in files_split_by_owners
           and not os.path.isfile(os.path.join(dir_with_owners, 'OWNERS'))):
      dir_with_owners = os.path.dirname(dir_with_owners)
    files_split_by_owners.setdefault(dir_with_owners, []).append((action, path))
  return files_split_by_owners


def PrintClInfo(cl_index, num_cls, directories, file_paths, description,
                reviewers, enable_auto_submit, topic):
  """Prints info about a CL.

  Args:
    cl_index: The index of this CL in the list of CLs to upload.
    num_cls: The total number of CLs that will be uploaded.
    directories: Paths to directories that contains the OWNERS files for which
        to upload a CL.
    file_paths: A list of files in this CL.
    description: The CL description.
    reviewers: A set of reviewers for this CL.
    enable_auto_submit: If the CL should also have auto submit enabled.
    topic: Topic to set for this CL.
  """
  description_lines = FormatDescriptionOrComment(description,
                                                 directories).splitlines()
  indented_description = '\n'.join(['    ' + l for l in description_lines])

  print('CL {}/{}'.format(cl_index, num_cls))
  print('Paths: {}'.format(FormatDirectoriesForPrinting(directories)))
  print('Reviewers: {}'.format(', '.join(reviewers)))
  print('Auto-Submit: {}'.format(enable_auto_submit))
  print('Topic: {}'.format(topic))
  print('\n' + indented_description + '\n')
  print('\n'.join(file_paths))
  print()


def SplitCl(description_file, comment_file, changelist, cmd_upload, dry_run,
            cq_dry_run, enable_auto_submit, max_depth, topic, repository_root):
  """"Splits a branch into smaller branches and uploads CLs.

  Args:
    description_file: File containing the description of uploaded CLs.
    comment_file: File containing the comment of uploaded CLs.
    changelist: The Changelist class.
    cmd_upload: The function associated with the git cl upload command.
    dry_run: Whether this is a dry run (no branches or CLs created).
    cq_dry_run: If CL uploads should also do a cq dry run.
    enable_auto_submit: If CL uploads should also enable auto submit.
    max_depth: The maximum directory depth to search for OWNERS files. A value
               less than 1 means no limit.
    topic: Topic to associate with split CLs.

  Returns:
    0 in case of success. 1 in case of error.
  """
  description = AddUploadedByGitClSplitToDescription(
      gclient_utils.FileRead(description_file))
  comment = gclient_utils.FileRead(comment_file) if comment_file else None

  try:
    EnsureInGitRepository()

    cl = changelist()
    upstream = cl.GetCommonAncestorWithUpstream()
    files = [
        (action.strip(), f)
        for action, f in scm.GIT.CaptureStatus(repository_root, upstream)
    ]

    if not files:
      print('Cannot split an empty CL.')
      return 1

    author = git.run('config', 'user.email').strip() or None
    refactor_branch = git.current_branch()
    assert refactor_branch, "Can't run from detached branch."
    refactor_branch_upstream = git.upstream(refactor_branch)
    assert refactor_branch_upstream, \
        "Branch %s must have an upstream." % refactor_branch

    if not CheckDescriptionBugLink(description):
      return 0

    files_split_by_reviewers = SelectReviewersForFiles(cl, author, files,
                                                       max_depth)

    num_cls = len(files_split_by_reviewers)
    print('Will split current branch (' + refactor_branch + ') into ' +
          str(num_cls) + ' CLs.\n')
    if cq_dry_run and num_cls > CL_SPLIT_FORCE_LIMIT:
      print(
        'This will generate "%r" CLs. This many CLs can potentially generate'
        ' too much load on the build infrastructure. Please email'
        ' infra-dev@chromium.org to ensure that this won\'t  break anything.'
        ' The infra team reserves the right to cancel your jobs if they are'
        ' overloading the CQ.' % num_cls)
      answer = gclient_utils.AskForData('Proceed? (y/n):')
      if answer.lower() != 'y':
        return 0

    cls_per_reviewer = collections.defaultdict(int)
    for cl_index, (reviewers, cl_info) in \
        enumerate(files_split_by_reviewers.items(), 1):
      # Convert reviewers from tuple to set.
      reviewer_set = set(reviewers)
      if dry_run:
        file_paths = [f for _, f in cl_info.files]
        PrintClInfo(cl_index, num_cls, cl_info.owners_directories, file_paths,
                    description, reviewer_set, enable_auto_submit, topic)
      else:
        UploadCl(refactor_branch, refactor_branch_upstream,
                 cl_info.owners_directories, cl_info.files, description,
                 comment, reviewer_set, changelist, cmd_upload, cq_dry_run,
                 enable_auto_submit, topic, repository_root)

      for reviewer in reviewers:
        cls_per_reviewer[reviewer] += 1

    # List the top reviewers that will be sent the most CLs as a result of the
    # split.
    reviewer_rankings = sorted(cls_per_reviewer.items(),
                               key=lambda item: item[1],
                               reverse=True)
    print('The top reviewers are:')
    for reviewer, count in reviewer_rankings[:CL_SPLIT_TOP_REVIEWERS]:
      print(f'    {reviewer}: {count} CLs')

    # Go back to the original branch.
    git.run('checkout', refactor_branch)

  except subprocess2.CalledProcessError as cpe:
    sys.stderr.write(cpe.stderr)
    return 1
  return 0


def CheckDescriptionBugLink(description):
  """Verifies that the description contains a bug link.

  Examples:
      Bug: 123
      Bug: chromium:456

  Prompts user if the description does not contain a bug link.
  """
  bug_pattern = re.compile(r"^Bug:\s*(?:[a-zA-Z]+:)?[0-9]+", re.MULTILINE)
  matches = re.findall(bug_pattern, description)
  answer = 'y'
  if not matches:
    answer = gclient_utils.AskForData(
        'Description does not include a bug link. Proceed? (y/n):')
  return answer.lower() == 'y'


def SelectReviewersForFiles(cl, author, files, max_depth):
  """Selects reviewers for passed-in files

  Args:
    cl: Changelist class instance
    author: Email of person running 'git cl split'
    files: List of files
    max_depth: The maximum directory depth to search for OWNERS files. A value
               less than 1 means no limit.
  """
  info_split_by_owners = GetFilesSplitByOwners(files, max_depth)

  info_split_by_reviewers = {}

  for (directory, split_files) in info_split_by_owners.items():
    # Use '/' as a path separator in the branch name and the CL description
    # and comment.
    directory = directory.replace(os.path.sep, '/')
    file_paths = [f for _, f in split_files]
    # Convert reviewers list to tuple in order to use reviewers as key to
    # dictionary.
    reviewers = tuple(
        cl.owners_client.SuggestOwners(
            file_paths, exclude=[author, cl.owners_client.EVERYONE]))

    if not reviewers in info_split_by_reviewers:
      info_split_by_reviewers[reviewers] = FilesAndOwnersDirectory([], [])
    info_split_by_reviewers[reviewers].files.extend(split_files)
    info_split_by_reviewers[reviewers].owners_directories.append(directory)

  return info_split_by_reviewers