git_footers.py

#!/usr/bin/env python3
# Copyright 2014 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.

import argparse
import json
import re
import sys

from collections import defaultdict

import git_common as git


FOOTER_PATTERN = re.compile(r'^\s*([\w-]+): *(.*)$')
CHROME_COMMIT_POSITION_PATTERN = re.compile(r'^([\w/\-\.]+)@{#(\d+)}$')
FOOTER_KEY_BLOCKLIST = set(['http', 'https'])


def normalize_name(header):
  return '-'.join([ word.title() for word in header.strip().split('-') ])


def parse_footer(line):
  """Returns footer's (key, value) if footer is valid, else None."""
  match = FOOTER_PATTERN.match(line)
  if match and match.group(1) not in FOOTER_KEY_BLOCKLIST:
    return (match.group(1), match.group(2))
  return None


def parse_footers(message):
  """Parses a git commit message into a multimap of footers."""
  _, _, parsed_footers = split_footers(message)
  footer_map = defaultdict(list)
  if parsed_footers:
    # Read footers from bottom to top, because latter takes precedense,
    # and we want it to be first in the multimap value.
    for (k, v) in reversed(parsed_footers):
      footer_map[normalize_name(k)].append(v.strip())
  return footer_map


def matches_footer_key(line, key):
  """Returns whether line is a valid footer whose key matches a given one.

  Keys are compared in normalized form.
  """
  r = parse_footer(line)
  if r is None:
    return False
  return normalize_name(r[0]) == normalize_name(key)


def split_footers(message):
  """Returns (non_footer_lines, footer_lines, parsed footers).

  Guarantees that:
    (non_footer_lines + footer_lines) ~= message.splitlines(), with at
      most one new newline, if the last paragraph is text followed by footers.
    parsed_footers is parse_footer applied on each line of footer_lines.
      There could be fewer parsed_footers than footer lines if some lines in
      last paragraph are malformed.
  """
  message_lines = list(message.rstrip().splitlines())
  footer_lines = []
  maybe_footer_lines = []
  for line in reversed(message_lines):
    if line == '' or line.isspace():
      break

    if parse_footer(line):
      footer_lines.extend(maybe_footer_lines)
      maybe_footer_lines = []
      footer_lines.append(line)
    else:
      # We only want to include malformed lines if they are preceded by
      # well-formed lines. So keep them in holding until we see a well-formed
      # line (case above).
      maybe_footer_lines.append(line)
  else:
    # The whole description was consisting of footers,
    # which means those aren't footers.
    footer_lines = []

  footer_lines.reverse()
  footers = [footer for footer in map(parse_footer, footer_lines) if footer]
  if not footers:
    return message_lines, [], []
  if maybe_footer_lines:
    # If some malformed lines were left over, add a newline to split them
    # from the well-formed ones.
    return message_lines[:-len(footer_lines)] + [''], footer_lines, footers
  return message_lines[:-len(footer_lines)], footer_lines, footers


def get_footer_change_id(message):
  """Returns a list of Gerrit's ChangeId from given commit message."""
  return parse_footers(message).get(normalize_name('Change-Id'), [])


def add_footer_change_id(message, change_id):
  """Returns message with Change-ID footer in it.

  Assumes that Change-Id is not yet in footers, which is then inserted at
  earliest footer line which is after all of these footers:
    Bug|Issue|Test|Feature.
  """
  assert 'Change-Id' not in parse_footers(message)
  return add_footer(message, 'Change-Id', change_id,
                    after_keys=['Bug', 'Issue', 'Test', 'Feature'])


def add_footer(message, key, value, after_keys=None, before_keys=None):
  """Returns a message with given footer appended.

  If after_keys and before_keys are both None (default), appends footer last.
  If after_keys is provided and matches footers already present, inserts footer
  as *early* as possible while still appearing after all provided keys, even
  if doing so conflicts with before_keys.
  If before_keys is provided, inserts footer as late as possible while still
  appearing before all provided keys.

  For example, given
      message='Header.\n\nAdded: 2016\nBug: 123\nVerified-By: CQ'
      after_keys=['Bug', 'Issue']
  the new footer will be inserted between Bug and Verified-By existing footers.
  """
  assert key == normalize_name(key), 'Use normalized key'
  new_footer = '%s: %s' % (key, value)
  if not FOOTER_PATTERN.match(new_footer):
    raise ValueError('Invalid footer %r' % new_footer)

  top_lines, footer_lines, _ = split_footers(message)
  if not footer_lines:
    if not top_lines or top_lines[-1] != '':
      top_lines.append('')
    footer_lines = [new_footer]
  else:
    after_keys = set(map(normalize_name, after_keys or []))
    after_indices = [
        footer_lines.index(x) for x in footer_lines for k in after_keys
        if matches_footer_key(x, k)]
    before_keys = set(map(normalize_name, before_keys or []))
    before_indices = [
        footer_lines.index(x) for x in footer_lines for k in before_keys
        if matches_footer_key(x, k)]
    if after_indices:
      # after_keys takes precedence, even if there's a conflict.
      insert_idx = max(after_indices) + 1
    elif before_indices:
      insert_idx = min(before_indices)
    else:
      insert_idx = len(footer_lines)
    footer_lines.insert(insert_idx, new_footer)
  return '\n'.join(top_lines + footer_lines)


def remove_footer(message, key):
  """Returns a message with all instances of given footer removed."""
  key = normalize_name(key)
  top_lines, footer_lines, _ = split_footers(message)
  if not footer_lines:
    return message
  new_footer_lines = []
  for line in footer_lines:
    try:
      f = normalize_name(parse_footer(line)[0])
      if f != key:
        new_footer_lines.append(line)
    except TypeError:
      # If the footer doesn't parse (i.e. is malformed), just let it carry over.
      new_footer_lines.append(line)
  return '\n'.join(top_lines + new_footer_lines)


def get_unique(footers, key):
  key = normalize_name(key)
  values = footers[key]
  assert len(values) <= 1, 'Multiple %s footers' % key
  if values:
    return values[0]

  return None


def get_position(footers):
  """Get the commit position from the footers multimap using a heuristic.

  Returns:
    A tuple of the branch and the position on that branch. For example,

    Cr-Commit-Position: refs/heads/main@{#292272}

    would give the return value ('refs/heads/main', 292272).
  """

  position = get_unique(footers, 'Cr-Commit-Position')
  if position:
    match = CHROME_COMMIT_POSITION_PATTERN.match(position)
    assert match, 'Invalid Cr-Commit-Position value: %s' % position
    return (match.group(1), match.group(2))

  raise ValueError('Unable to infer commit position from footers')


def main(args):
  parser = argparse.ArgumentParser(
    formatter_class=argparse.ArgumentDefaultsHelpFormatter
  )
  parser.add_argument('ref', nargs='?', help='Git ref to retrieve footers from.'
                      ' Omit to parse stdin.')

  g = parser.add_mutually_exclusive_group()
  g.add_argument('--key', metavar='KEY',
                 help='Get all values for the given footer name, one per '
                 'line (case insensitive)')
  g.add_argument('--position', action='store_true')
  g.add_argument('--position-ref', action='store_true')
  g.add_argument('--position-num', action='store_true')
  g.add_argument('--json', help='filename to dump JSON serialized footers to.')

  opts = parser.parse_args(args)

  if opts.ref:
    message = git.run('log', '-1', '--format=%B', opts.ref)
  else:
    message = sys.stdin.read()

  footers = parse_footers(message)

  if opts.key:
    for v in footers.get(normalize_name(opts.key), []):
      print(v)
  elif opts.position:
    pos = get_position(footers)
    print('%s@{#%s}' % (pos[0], pos[1] or '?'))
  elif opts.position_ref:
    print(get_position(footers)[0])
  elif opts.position_num:
    pos = get_position(footers)
    assert pos[1], 'No valid position for commit'
    print(pos[1])
  elif opts.json:
    with open(opts.json, 'w') as f:
      json.dump(footers, f)
  else:
    for k in footers.keys():
      for v in footers[k]:
        print('%s: %s' % (k, v))
  return 0


if __name__ == '__main__':
  try:
    sys.exit(main(sys.argv[1:]))
  except KeyboardInterrupt:
    sys.stderr.write('interrupted\n')
    sys.exit(1)