byteify-strings: add --inplace option to write back result

contrib/byteify-strings.py

@@ -1,175 +1,209 b''
 #!/usr/bin/env python3
 #
 # byteify-strings.py - transform string literals to be Python 3 safe
 #
 # Copyright 2015 Gregory Szorc <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 import argparse
+import contextlib
+import errno
 import io
+import os
 import sys
+import tempfile
 import token
 import tokenize
 
 if True:
     def replacetokens(tokens, fullname):
         """Transform a stream of tokens from raw to Python 3.
 
         Returns a generator of possibly rewritten tokens.
 
         The input token list may be mutated as part of processing. However,
         its changes do not necessarily match the output token stream.
         """
         futureimpline = False
 
         # The following utility functions access the tokens list and i index of
         # the for i, t enumerate(tokens) loop below
         def _isop(j, *o):
             """Assert that tokens[j] is an OP with one of the given values"""
             try:
                 return tokens[j].type == token.OP and tokens[j].string in o
             except IndexError:
                 return False
 
         def _findargnofcall(n):
             """Find arg n of a call expression (start at 0)
 
             Returns index of the first token of that argument, or None if
             there is not that many arguments.
 
             Assumes that token[i + 1] is '('.
 
             """
             nested = 0
             for j in range(i + 2, len(tokens)):
                 if _isop(j, ')', ']', '}'):
                     # end of call, tuple, subscription or dict / set
                     nested -= 1
                     if nested < 0:
                         return None
                 elif n == 0:
                     # this is the starting position of arg
                     return j
                 elif _isop(j, '(', '[', '{'):
                     nested += 1
                 elif _isop(j, ',') and nested == 0:
                     n -= 1
 
             return None
 
         def _ensureunicode(j):
             """Make sure the token at j is a unicode string
 
             This rewrites a string token to include the unicode literal prefix
             so the string transformer won't add the byte prefix.
 
             Ignores tokens that are not strings. Assumes bounds checking has
             already been done.
 
             """
             st = tokens[j]
             if st.type == token.STRING and st.string.startswith(("'", '"')):
                 tokens[j] = st._replace(string='u%s' % st.string)
 
         for i, t in enumerate(tokens):
             # Convert most string literals to byte literals. String literals
             # in Python 2 are bytes. String literals in Python 3 are unicode.
             # Most strings in Mercurial are bytes and unicode strings are rare.
             # Rather than rewrite all string literals to use ``b''`` to indicate
             # byte strings, we apply this token transformer to insert the ``b``
             # prefix nearly everywhere.
             if t.type == token.STRING:
                 s = t.string
 
                 # Preserve docstrings as string literals. This is inconsistent
                 # with regular unprefixed strings. However, the
                 # "from __future__" parsing (which allows a module docstring to
                 # exist before it) doesn't properly handle the docstring if it
                 # is b''' prefixed, leading to a SyntaxError. We leave all
                 # docstrings as unprefixed to avoid this. This means Mercurial
                 # components touching docstrings need to handle unicode,
                 # unfortunately.
                 if s[0:3] in ("'''", '"""'):
                     yield t
                     continue
 
                 # If the first character isn't a quote, it is likely a string
                 # prefixing character (such as 'b', 'u', or 'r'. Ignore.
                 if s[0] not in ("'", '"'):
                     yield t
                     continue
 
                 # String literal. Prefix to make a b'' string.
                 yield t._replace(string='b%s' % t.string)
                 continue
 
             # Insert compatibility imports at "from __future__ import" line.
             # No '\n' should be added to preserve line numbers.
             if (t.type == token.NAME and t.string == 'import' and
                 all(u.type == token.NAME for u in tokens[i - 2:i]) and
                 [u.string for u in tokens[i - 2:i]] == ['from', '__future__']):
                 futureimpline = True
             if t.type == token.NEWLINE and futureimpline:
                 futureimpline = False
                 if fullname == 'mercurial.pycompat':
                     yield t
                     continue
                 r, c = t.start
                 l = (b'; from mercurial.pycompat import '
                      b'delattr, getattr, hasattr, setattr, xrange, '
                      b'open, unicode\n')
                 for u in tokenize.tokenize(io.BytesIO(l).readline):
                     if u.type in (tokenize.ENCODING, token.ENDMARKER):
                         continue
                     yield u._replace(
                         start=(r, c + u.start[1]), end=(r, c + u.end[1]))
                 continue
 
             # This looks like a function call.
             if t.type == token.NAME and _isop(i + 1, '('):
                 fn = t.string
 
                 # *attr() builtins don't accept byte strings to 2nd argument.
                 if (fn in ('getattr', 'setattr', 'hasattr', 'safehasattr') and
                         not _isop(i - 1, '.')):
                     arg1idx = _findargnofcall(1)
                     if arg1idx is not None:
                         _ensureunicode(arg1idx)
 
                 # .encode() and .decode() on str/bytes/unicode don't accept
                 # byte strings on Python 3.
                 elif fn in ('encode', 'decode') and _isop(i - 1, '.'):
                     for argn in range(2):
                         argidx = _findargnofcall(argn)
                         if argidx is not None:
                             _ensureunicode(argidx)
 
                 # It changes iteritems/values to items/values as they are not
                 # present in Python 3 world.
                 elif fn in ('iteritems', 'itervalues'):
                     yield t._replace(string=fn[4:])
                     continue
 
             # Emit unmodified token.
             yield t
 
 def process(fin, fout):
     tokens = tokenize.tokenize(fin.readline)
     tokens = replacetokens(list(tokens), fullname='<dummy>')
     fout.write(tokenize.untokenize(tokens))
 
+def tryunlink(fname):
+    try:
+        os.unlink(fname)
+    except OSError as err:
+        if err.errno != errno.ENOENT:
+            raise
+
[e-mail]
+def editinplace(fname):
+    n = os.path.basename(fname)
+    d = os.path.dirname(fname)
+    fp = tempfile.NamedTemporaryFile(prefix='.%s-' % n, suffix='~', dir=d,
+                                     delete=False)
+    try:
+        yield fp
+        fp.close()
+        if os.name == 'nt':
+            tryunlink(fname)
+        os.rename(fp.name, fname)
+    finally:
+        fp.close()
+        tryunlink(fp.name)
+
 def main():
     ap = argparse.ArgumentParser()
+    ap.add_argument('-i', '--inplace', action='store_true', default=False,
+                    help='edit files in place')
     ap.add_argument('files', metavar='FILE', nargs='+', help='source file')
     args = ap.parse_args()
     for fname in args.files:
+        if args.inplace:
+            with editinplace(fname) as fout:
+                with open(fname, 'rb') as fin:
+                    process(fin, fout)
+        else:
         with open(fname, 'rb') as fin:
             fout = sys.stdout.buffer
             process(fin, fout)
 
 if __name__ == '__main__':
     main()