codemod.py

#!/usr/bin/env python

# Copyright (c) 2007-2008 Facebook
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# See accompanying file LICENSE.
#
# @author Justin Rosenstein

r"""
codemod.py is a tool/library to assist you with large-scale codebase refactors
that can be partially automated but still require human oversight and
occassional intervention.

Example: Let's say you're deprecating your use of the <font> tag.  From the
command line, you might make progress by running:

  codemod.py -m -d /home/jrosenstein/www --extensions php,html \
             '<font *color="?(.*?)"?>(.*?)</font>' \
             '<span style="color: \1;">\2</span>'

For each match of the regex, you'll be shown a colored diff, and asked if you
want to accept the change (the replacement of the <font> tag with a <span>
tag), reject it, or edit the line in question in your $EDITOR of choice.

Usage: last two arguments are a regular expression to match and a substitution
       string, respectively.  Or you can omit the substitution string, and just
       be prompted on each match for whether you want to edit in your editor.

Options (all optional) include:

  -m
    Have regex work over multiple lines (e.g. have dot match newlines).  By
    default, codemod applies the regex one line at a time.
  -d
    The path whose ancestor files are to be explored.  Defaults to current dir.
  --start
    A path:line_number-formatted position somewhere in the hierarchy from which
    to being exploring, or a percentage (e.g. "--start 25%") of the way through
    to start.  Useful if you're divvying up the substitution task across
    multiple people.
  --end
    A path:line_number-formatted position somewhere in the hierarchy just
    *before* which we should stop exploring, or a percentage of the way
    through, just before which to end.
  --extensions
    A comma-delimited list of file extensions to process.
  --editor
    Specify an editor, e.g. "vim" or "emacs".  If omitted, defaults to $EDITOR
    environment variable.
  --count
    Don't run normally.  Instead, just print out number of times places in the
    codebase where the 'query' matches.
  --test
    Don't run normally.  Instead, just run the unit tests embedded in the
    codemod library.

You can also use codemod for transformations that are much more sophisticated
than regular expression substitution.  Rather than using the command line, you
write Python code that looks like:

  import codemod
  codemod.Query(...).run_interactive()

See the documentation for the Query class for details.

@author Justin Rosenstein
"""


import sys, os

def path_filter(extensions=None, exclude_paths=[]):
  """
  Returns a function (useful as the path_filter field of a Query instance)
  that returns True iff the path it is given has an extension one of the
  file extensions specified in `extensions`, an array of strings.

  >>> map(path_filter(extensions=['js', 'php']), ['./profile.php', './q.jjs'])
  [True, False]
  >>> map(path_filter(exclude_paths=['html']), ['./html/x.php', './lib/y.js'])
  [False, True]
  """
  def the_filter(path):
    if extensions:
      if not any(path.endswith('.' + extension) for extension in extensions):
        return False
    for excluded in exclude_paths:
      if path.startswith(excluded) or path.startswith('./' + excluded):
        return False
    return True
  return the_filter

_default_path_filter = path_filter(
  extensions=['php', 'phpt', 'js', 'css', 'rb', 'erb']
)

def run_interactive(query, editor=None, just_count=False):
  """
  Asks the user about each patch suggested by the result of the query.

  @param query        An instance of the Query class.
  @param editor       Name of editor to use for manual intervention, e.g. 'vim'
                      or 'emacs'.  If omitted/None, defaults to $EDITOR
                      environment variable.
  @param just_count   If true: don't run normally.  Just print out number of
                      places in the codebase where the query matches.
  """

  # Load start from bookmark, if appropriate.
  bookmark = _load_bookmark()
  if bookmark:
    print 'Resume where you left off, at %s (y/n)? ' % str(bookmark),
    if (_prompt(default='y') == 'y'):
      query.start_position = bookmark

  # Okay, enough of this foolishness of computing start and end.
  # Let's ask the user about some one line diffs!
  print 'Searching for first instance...'
  suggestions = query.generate_patches()

  if just_count:
    for count, _ in enumerate(suggestions):
      terminal_move_to_beginning_of_line()
      print count,
      sys.stdout.flush()  # since print statement ends in comma
    print
    return

  for patch in suggestions:
    _save_bookmark(patch.start_position)
    _ask_about_patch(patch, editor)
    print 'Searching...'
  _delete_bookmark()

def line_transformation_suggestor(line_transformation, line_filter=None):
  """
  Returns a suggestor (a function that takes a list of lines and yields
  patches) where suggestions are the result of line-by-line transformations.

  @param line_transformation  Function that, given a line, returns another line
                              with which to replace the given one.  If the
                              output line is different from the input line, the
                              user will be prompted about whether to make the
                              change.  If the output is None, this means "I
                              don't have a suggestion, but the user should
                              still be asked if zhe wants to edit the line."
  @param line_filter          Given a line, returns True or False.  If False,
                              a line is ignored (as if line_transformation
                              returned the line itself for that line).
  """
  def suggestor(lines):
    for line_number, line in enumerate(lines):
      if line_filter and not line_filter(line):
        continue
      candidate = line_transformation(line)
      if candidate is None:
        yield Patch(line_number)
      else:
        yield Patch(line_number, new_lines=[candidate])
  return suggestor

def regex_suggestor(regex, substitution=None, line_filter=None):
  if isinstance(regex, str):
    import re
    regex = re.compile(regex)

  if substitution is None:
    line_transformation = lambda line: None if regex.search(line) else line
  else:
    line_transformation = lambda line: regex.sub(substitution, line)
  return line_transformation_suggestor(line_transformation, line_filter)

def multiline_regex_suggestor(regex, substitution=None):
  """
  Return a suggestor function which, given a list of lines, generates patches
  to substitute matches of the given regex with (if provided) the given
  substitution.

  @param regex         Either a regex object or a string describing a regex.
  @param substitution  Either None (meaning that we should flag the matches
                       without suggesting an alternative), or a string (using
                       \1 notation to backreference match groups) or a
                       function (that takes a match object as input).
  """
  import re
  if isinstance(regex, str):
    regex = re.compile(regex, re.DOTALL)

  if isinstance(substitution, str):
    substitution_func = lambda match: match.expand(substitution)
  else:
    substitution_func = substitution

  def suggestor(lines):
    pos = 0
    while True:
      match = regex.search(''.join(lines), pos)
      if not match:
        break
      start_row, start_col = _index_to_row_col(lines, match.start())
      end_row,   end_col   = _index_to_row_col(lines, match.end()-1)

      if substitution is None:
        new_lines = None
      else:
        # TODO: ugh, this is hacky.  Clearly I need to rewrite this to use
        #       character-level patches, rather than line-level patches.
        new_lines = substitution_func(match)
        if new_lines is not None:
          new_lines = ''.join((
            lines[start_row][:start_col],
            new_lines,
            lines[end_row][end_col+1:]
          ))

      yield Patch(
        start_line_number = start_row,
        end_line_number   = end_row + 1,
        new_lines         = new_lines
      )
      pos = match.start() + 1

  return suggestor

def _index_to_row_col(lines, index):
  r"""
  >>> lines = ['hello\n', 'world\n']
  >>> _index_to_row_col(lines, 0)
  (0, 0)
  >>> _index_to_row_col(lines, 7)
  (1, 1)
  """
  if index < 0:
    raise IndexError('negative index')
  current_index = 0
  for line_number, line in enumerate(lines):
    line_length = len(line)
    if current_index + line_length > index:
      return line_number, index - current_index
    current_index += line_length
  raise IndexError('index %d out of range' % index)


class Query:
  """
  Represents a suggestor, along with a set of constraints on which files
  should be fed to that suggestor.

  >>> Query(lambda x: None, start='profile.php:20').start_position
  Position('profile.php', 20)
  """

  def __init__(self,
               suggestor,
               start=None,
               end=None,
               root_directory='.',
               path_filter=_default_path_filter):
    """
    @param suggestor            A function that takes a list of lines and
                                generates instances of Patch to suggest.
                                (Patches should not specify paths.)
    @param start                One of:
                                - an instance of Position (indicating the place
                                  in the file hierarchy at which to resume),
                                - a path:line_number-formatted string
                                  representing a position,
                                - a string formatted like "25%" (indicating we
                                  should start 25% of the way through the
                                  process), or
                                - None (indicating that we should start at the
                                  beginning).
    @param end                  An indicator of the position just *before* which
                                to stop exploring, using one of the same formats
                                used for start (where None means 'traverse to
                                the end of the hierarchy).
    @param root_directory       The path whose ancestor files are to be explored.
    @param path_filter          Given a path, returns True or False.  If False,
                                the entire file is ignored.
    """
    self.suggestor          = suggestor
    self._start             = start
    self._end               = end
    self.root_directory     = root_directory
    self.path_filter        = path_filter
    self._all_patches_cache = None

  def clone(self):
    import copy
    return copy.copy(self)

  def _get_position(self, attr_name):
    attr_value = getattr(self, attr_name)
    if attr_value is None:
      return None
    if isinstance(attr_value, str) and attr_value.endswith('%'):
      attr_value = self.compute_percentile(int(attr_value[:-1]))
      setattr(self, attr_name, attr_value)
    return Position(attr_value)

  def get_start_position(self):
    return self._get_position('_start')
  start_position = property(get_start_position)

  def get_end_position(self):
    return self._get_position('_end')
  end_position = property(get_end_position)

  def get_all_patches(self, dont_use_cache=False):
    """
    Computes a list of all patches matching this query, though ignoreing
    self.start_position and self.end_position.

    @param dont_use_cache   If False, and get_all_patches has been called
                            before, compute the list computed last time.
    """
    if not dont_use_cache and self._all_patches_cache is not None:
      return self._all_patches_cache

    print 'Computing full change list (since you specified a percentage)...',
    sys.stdout.flush()  # since print statement ends in comma

    endless_query = self.clone()
    endless_query.start_position = endless_query.end_position = None
    self._all_patches_cache = list(endless_query.generate_patches())
    return self._all_patches_cache

  def compute_percentile(self, percentage):
    """
    Returns a Position object that represents percentage%-far-of-the-way
    through the larger task, as specified by this query.

    @param percentage    a number between 0 and 100.
    """
    all_patches = self.get_all_patches()
    return all_patches[int(len(all_patches) * percentage / 100)].start_position

  def generate_patches(self):
    """
    Generates a list of patches for each file underneath self.root_directory
    that satisfy the given conditions given query conditions, where patches for
    each file are suggested by self.suggestor.
    """
    start_pos = self.start_position or Position(None, None)
    end_pos   = self.end_position   or Position(None, None)

    path_list = Query._walk_directory(self.root_directory)
    path_list = Query._sublist(path_list, start_pos.path, end_pos.path)
    path_list = (path for path in path_list if
                 Query._path_looks_like_code(path) and self.path_filter(path))

    for path in path_list:

      lines = list(open(path))
      for patch in self.suggestor(lines):
        if path == start_pos.path:
          if patch.start_line_number < start_pos.line_number:
            continue  # suggestion is pre-start_pos
        if path == end_pos.path:
          if patch.end_line_number >= end_pos.line_number:
            break  # suggestion is post-end_pos

        old_lines = lines[patch.start_line_number:patch.end_line_number]
        if patch.new_lines is None or patch.new_lines != old_lines:
          patch.path = path
          yield patch
          lines[:] = list(open(path))  # re-open file, in case contents changed

  def run_interactive(self, **kargs):
    run_interactive(self, **kargs)

  @staticmethod
  def _walk_directory(root_directory):
    """
    Generates the paths of all files that are ancestors of `root_directory`.
    """

    paths = [os.path.join(root, name)
             for root, dirs, files in os.walk(root_directory)
             for name in files]
    paths.sort()
    return paths

  @staticmethod
  def _sublist(list, starting_value, ending_value = None):
    """
    >>> list(Query._sublist((x*x for x in xrange(1, 100)), 16, 64))
    [16, 25, 36, 49, 64]
    """
    have_started = starting_value is None

    for x in list:
      have_started = have_started or x == starting_value
      if have_started:
        yield x

      if ending_value is not None and x == ending_value:
        break

  @staticmethod
  def _path_looks_like_code(path):
    """
    >>> Query._path_looks_like_code('/home/jrosenstein/www/profile.php')
    True
    >>> Query._path_looks_like_code('./tags')
    False
    >>> Query._path_looks_like_code('/home/jrosenstein/www/profile.php~')
    False
    >>> Query._path_looks_like_code('/home/jrosenstein/www/.git/HEAD')
    False
    """
    return ('/.' not in path and path[-1] != '~'
            and not path.endswith('tags')
            and not path.endswith('TAGS'))


class Position:
  """
  >>> p1, p2 = Position('./hi.php', 20), Position('./hi.php:20')
  >>> p1.path == p2.path and p1.line_number == p2.line_number
  True
  >>> p1
  Position('./hi.php', 20)
  >>> print p1
  ./hi.php:20
  >>> Position(p1)
  Position('./hi.php', 20)
  """

  def __init__(self, *path_and_line_number):
    """
    You can use the two parameter version, and pass a path and line number, or
    you can use the one parameter version, and pass a $path:$line_number string,
    or another instance of Position to copy.
    """
    if len(path_and_line_number) == 2:
      self.path, self.line_number = path_and_line_number
    elif len(path_and_line_number) == 1:
      arg = path_and_line_number[0]
      if isinstance(arg, Position):
        self.path, self.line_number = arg.path, arg.line_number
      else:
        try:
          self.path, line_number_s = arg.split(':')
          self.line_number = int(line_number_s)
        except ValueError:
          raise ValueError('inappropriately formatted Position string: %s'
                           % path_and_line_number[0])
    else:
      raise TypeError('Position takes 1 or 2 arguments')

  def __repr__(self):
    return 'Position(%s, %d)' % (repr(self.path), self.line_number)

  def __str__(self):
    return '%s:%d' % (self.path, self.line_number)


class Patch:
  """
  Represents a range of a file and (optionally) a list of lines with which to
  replace that range.

  >>> p = Patch(2, 4, ['X', 'Y', 'Z'], 'x.php')
  >>> print p.render_range()
  x.php:2-3
  >>> p.start_position
  Position('x.php', 2)
  >>> l = ['a', 'b', 'c', 'd', 'e', 'f']
  >>> p.apply_to(l)
  >>> l
  ['a', 'b', 'X', 'Y', 'Z', 'e', 'f']
  """
  def __init__(self, start_line_number, end_line_number=None, new_lines=None,
               path=None):
    """
    Constructs a Patch object.

    @param end_line_number  The line number just *after* the end of the range.
                            Defaults to start_line_number + 1, i.e. a one-line
                            diff.
    @param new_lines        The set of lines with which to replace the range
                            specified, or a newline-delimited string.  Omitting
                            this means that this "patch" doesn't actually
                            suggest a change.
    @param path             Path is optional only so that suggestors that have
                            been passed a list of lines don't have to set the
                            path explicitly.  (It'll get set by the suggestor's
                            caller.)
    """
    if end_line_number is None:
      end_line_number = start_line_number + 1
    if isinstance(new_lines, str):
      new_lines = new_lines.splitlines(True)
    for k, v in locals().iteritems():
      setattr(self, k, v)
  def __repr__(self):
    return 'Patch()' % ', '.join(map(repr, [
        self.path, self.start_line_number, self.end_line_number, self.new_lines
      ]))
  def apply_to(self, lines):
    if self.new_lines is None:
      raise ValueError('Can\'t apply patch without suggested new lines.')
    lines[self.start_line_number:self.end_line_number] = self.new_lines
  def render_range(self):
    path = self.path or '<unknown>'
    if self.start_line_number == self.end_line_number - 1:
      return '%s:%d' % (path, self.start_line_number)
    else:
      return '%s:%d-%d' % (path,
          self.start_line_number, self.end_line_number - 1)
  def get_start_position(self):
    return Position(self.path, self.start_line_number)
  start_position = property(get_start_position)


def print_patch(patch, lines_to_print, file_lines=None):
  from math import floor, ceil

  if file_lines is None:
    file_lines = list(open(patch.path))

  size_of_old               = patch.end_line_number - patch.start_line_number
  size_of_new               = len(patch.new_lines) if patch.new_lines else 0
  size_of_diff              = size_of_old + size_of_new
  size_of_context           = max(0, lines_to_print - size_of_diff)
  size_of_up_context        = int(size_of_context / 2)
  size_of_down_context      = int(ceil(size_of_context / 2))
  start_context_line_number = patch.start_line_number - size_of_up_context
  end_context_line_number   = patch.end_line_number + size_of_down_context

  def print_file_line(line_number):
    print ('  %s' % file_lines[i]) if (0 <= i < len(file_lines)) else '~\n',

  for i in xrange(start_context_line_number, patch.start_line_number):
    print_file_line(i)
  for i in xrange(patch.start_line_number, patch.end_line_number):
    if patch.new_lines is not None:
      terminal_print('- %s' % file_lines[i], color='RED')
    else:
      terminal_print('* %s' % file_lines[i], color='YELLOW')
  if patch.new_lines is not None:
    for line in patch.new_lines:
      terminal_print('+ %s' % line, color='GREEN')
  for i in xrange(patch.end_line_number, end_context_line_number):
    print_file_line(i)


def _ask_about_patch(patch, editor):
  terminal_clear()
  terminal_print('%s\n' % patch.render_range(), color='WHITE')
  print

  lines = list(open(patch.path))
  print_patch(patch, terminal_get_size()[0] - 20, lines)

  print

  if patch.new_lines is not None:
    print 'Accept change (y = yes [default], n = no, e = edit, E = yes+edit)? ',
    p = _prompt('yneE', default='y')
  else:
    print '(e = edit [default], n = skip line)? ',
    p = _prompt('en', default='e')

  if p in 'yE':
    patch.apply_to(lines)
    _save(patch.path, lines)
  if p in 'eE':
    run_editor(patch.start_position, editor)


def _prompt(letters='yn', default=None):
  """
  Wait for the user to type a character (and hit Enter).  If the user enters
  one of the characters in `letters`, return that character.  If the user
  hits Enter without entering a character, and `default` is specified, returns
  `default`.  Otherwise, asks the user to enter a character again.
  """
  while True:
    try:
      input = sys.stdin.readline().strip()
    except KeyboardInterrupt:
      sys.exit(0)
    if input and input in letters:
      return input
    if default is not None and input == '':
      return default
    print 'Come again?'

def _save(path, lines):
  file_w = open(path, 'w')
  for line in lines:
    file_w.write(line)
  file_w.close()

def run_editor(position, editor=None):
  editor = editor or os.environ.get('EDITOR') or 'vim'
  os.system('%s +%d %s' % (editor, position.line_number + 1, position.path))


#
# Bookmarking functions.  codemod saves a file called .codemod.bookmark to
# keep track of where you were the last time you exited in the middle of
# an interactive sesh.
#

def _save_bookmark(position):
  file_w = open('.codemod.bookmark', 'w')
  file_w.write(str(position))
  file_w.close()

def _load_bookmark():
  try:
    file = open('.codemod.bookmark')
  except IOError:
    return None
  contents = file.readline().strip()
  file.close()
  return Position(contents)

def _delete_bookmark():
  try:
    os.remove('.codemod.bookmark')
  except OSError:
    pass  # file didn't exist


#
# Functions for working with the terminal.  Should probably be moved to a
# standalone library.
#

def terminal_get_size(default_size = (25, 80)):
  """
  Return (number of rows, number of columns) for the terminal, if they can be determined,
  or `default_size` if they can't.
  """

  def ioctl_GWINSZ(fd):                  #### TABULATION FUNCTIONS
    try:                                ### Discover terminal width
      import fcntl, termios, struct, os
      return struct.unpack('hh', fcntl.ioctl(fd, termios.TIOCGWINSZ, '1234'))
    except:
      return None

  # try open fds
  size = ioctl_GWINSZ(0) or ioctl_GWINSZ(1) or ioctl_GWINSZ(2)
  if not size:
    # ...then ctty
    try:
      fd = os.open(os.ctermid(), os.O_RDONLY)
      size = ioctl_GWINSZ(fd)
      os.close(fd)
    except:
      pass
  if not size:
    # env vars or finally defaults
    try:
      size = (env['LINES'], env['COLUMNS'])
    except:
      return default_size

  return map(int, size)

def terminal_clear():
  """
  Like calling the `clear` UNIX command.  If that fails, just prints a bunch
  of newlines :-P
  """
  if not _terminal_use_capability('clear'):
    print '\n' * 8

def terminal_move_to_beginning_of_line():
  """
  Jumps the cursor back to the beginning of the current line of text.
  """
  if not _terminal_use_capability('cr'):
    print

def _terminal_use_capability(capability_name):
  """
  If the terminal supports the given capability, output it.  Return whether
  it was output.
  """
  import curses, sys
  curses.setupterm()
  capability = curses.tigetstr(capability_name)
  if capability:
    sys.stdout.write(capability)
  return bool(capability)

def terminal_print(text, color):
  """Print text in the specified color, without a terminating newline."""
  _terminal_set_color(color)
  print text,
  _terminal_restore_color()

def _terminal_set_color(color):
  import curses, sys
  def color_code(set_capability, possible_colors):
    try:
      color_index = possible_colors.split(' ').index(color)
    except ValueError:
      return None
    set_code = curses.tigetstr(set_capability)
    if not set_code:
      return None
    return curses.tparm(set_code, color_index)
  code = (color_code('setaf', 'BLACK RED GREEN YELLOW BLUE MAGENTA CYAN WHITE')
       or color_code('setf', 'BLACK BLUE GREEN CYAN RED MAGENTA YELLOW WHITE'))
  if code:
    sys.stdout.write(code)

def _terminal_restore_color():
  import curses, sys
  sys.stdout.write(curses.tigetstr('sgr0'))

def print_through_less(text):
  """
  Prints `text` to standard output.  If `text` wouldn't fit on one screen (as
  measured by line count), make output scrollable a la `less`.
  """
  from tempfile import NamedTemporaryFile
  tempfile = NamedTemporaryFile()
  tempfile.write(text)
  tempfile.flush()
  os.system('less --quit-if-one-screen %s' % tempfile.name)


#
# Code to make this run as an executable from the command line.
#

class _UsageException(Exception): pass

def _parse_command_line():
  import getopt, sys, re
  try:
    opts, remaining_args = getopt.gnu_getopt(
        sys.argv[1:], 'md:',
        ['start=', 'end=', 'extensions=', 'editor=', 'count', 'test'])
  except getopt.error:
    raise _UsageException()
  opts = dict(opts)

  if '--test' in opts:
    import doctest
    doctest.testmod()
    sys.exit(0)

  query_options = {}
  if len(remaining_args) in [1, 2]:
    query_options['suggestor'] = (
     (multiline_regex_suggestor if '-m' in opts else regex_suggestor)
     (*remaining_args)  # remaining_args is [regex] or [regex, substitution].
    )
  else:
    raise _UsageException()
  if '--start' in opts:
    query_options['start'] = opts['--start']
  if '--end' in opts:
    query_options['end'] = opts['--end']
  if '-d' in opts:
    query_options['root_directory'] = opts['-d']
  if '--extensions' in opts:
    query_options['path_filter'] = (
        path_filter(extensions=opts['--extensions'].split(',')))

  options = {}
  options['query'] = Query(**query_options)
  if '--editor' in opts:
    options['editor'] = opts['--editor']
  if '--count' in opts:
    options['just_count'] = True

  return options

if __name__ == '__main__':
  try:
    options = _parse_command_line()
  except _UsageException:
    print_through_less(__doc__.strip())
    sys.exit(2)
  run_interactive(**options)