windows: add context manager support to mixedfilemodewrapper

I stumbled into this in the next patch.  The difference between getting a
context manager capable object or not from vfs classes was as subtle as adding a
'+' to the file mode.

mercurial/windows.py

@@ -1,466 +1,472 b''
 # windows.py - Windows utility function implementations for Mercurial
 #
 #  Copyright 2005-2009 Matt Mackall <[e-mail]> and others
 #
 # 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 errno
 import msvcrt
 import os
 import re
 import stat
 import sys
 
 from .i18n import _
 from . import (
     encoding,
     osutil,
     pycompat,
     win32,
 )
 
 try:
     import _winreg as winreg
     winreg.CloseKey
 except ImportError:
     import winreg
 
 executablepath = win32.executablepath
 getuser = win32.getuser
 hidewindow = win32.hidewindow
 makedir = win32.makedir
 nlinks = win32.nlinks
 oslink = win32.oslink
 samedevice = win32.samedevice
 samefile = win32.samefile
 setsignalhandler = win32.setsignalhandler
 spawndetached = win32.spawndetached
 split = os.path.split
 testpid = win32.testpid
 unlink = win32.unlink
 
 umask = 0o022
 
 class mixedfilemodewrapper(object):
     """Wraps a file handle when it is opened in read/write mode.
 
     fopen() and fdopen() on Windows have a specific-to-Windows requirement
     that files opened with mode r+, w+, or a+ make a call to a file positioning
     function when switching between reads and writes. Without this extra call,
     Python will raise a not very intuitive "IOError: [Errno 0] Error."
 
     This class wraps posixfile instances when the file is opened in read/write
     mode and automatically adds checks or inserts appropriate file positioning
     calls when necessary.
     """
     OPNONE = 0
     OPREAD = 1
     OPWRITE = 2
 
     def __init__(self, fp):
         object.__setattr__(self, r'_fp', fp)
         object.__setattr__(self, r'_lastop', 0)
 
+    def __enter__(self):
+        return self._fp.__enter__()
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self._fp.__exit__(exc_type, exc_val, exc_tb)
+
     def __getattr__(self, name):
         return getattr(self._fp, name)
 
     def __setattr__(self, name, value):
         return self._fp.__setattr__(name, value)
 
     def _noopseek(self):
         self._fp.seek(0, os.SEEK_CUR)
 
     def seek(self, *args, **kwargs):
         object.__setattr__(self, r'_lastop', self.OPNONE)
         return self._fp.seek(*args, **kwargs)
 
     def write(self, d):
         if self._lastop == self.OPREAD:
             self._noopseek()
 
         object.__setattr__(self, r'_lastop', self.OPWRITE)
         return self._fp.write(d)
 
     def writelines(self, *args, **kwargs):
         if self._lastop == self.OPREAD:
             self._noopeseek()
 
         object.__setattr__(self, r'_lastop', self.OPWRITE)
         return self._fp.writelines(*args, **kwargs)
 
     def read(self, *args, **kwargs):
         if self._lastop == self.OPWRITE:
             self._noopseek()
 
         object.__setattr__(self, r'_lastop', self.OPREAD)
         return self._fp.read(*args, **kwargs)
 
     def readline(self, *args, **kwargs):
         if self._lastop == self.OPWRITE:
             self._noopseek()
 
         object.__setattr__(self, r'_lastop', self.OPREAD)
         return self._fp.readline(*args, **kwargs)
 
     def readlines(self, *args, **kwargs):
         if self._lastop == self.OPWRITE:
             self._noopseek()
 
         object.__setattr__(self, r'_lastop', self.OPREAD)
         return self._fp.readlines(*args, **kwargs)
 
 def posixfile(name, mode='r', buffering=-1):
     '''Open a file with even more POSIX-like semantics'''
     try:
         fp = osutil.posixfile(name, mode, buffering) # may raise WindowsError
 
         # The position when opening in append mode is implementation defined, so
         # make it consistent with other platforms, which position at EOF.
         if 'a' in mode:
             fp.seek(0, os.SEEK_END)
 
         if '+' in mode:
             return mixedfilemodewrapper(fp)
 
         return fp
     except WindowsError as err:
         # convert to a friendlier exception
         raise IOError(err.errno, '%s: %s' % (name, err.strerror))
 
 class winstdout(object):
     '''stdout on windows misbehaves if sent through a pipe'''
 
     def __init__(self, fp):
         self.fp = fp
 
     def __getattr__(self, key):
         return getattr(self.fp, key)
 
     def close(self):
         try:
             self.fp.close()
         except IOError:
             pass
 
     def write(self, s):
         try:
             # This is workaround for "Not enough space" error on
             # writing large size of data to console.
             limit = 16000
             l = len(s)
             start = 0
             self.softspace = 0
             while start < l:
                 end = start + limit
                 self.fp.write(s[start:end])
                 start = end
         except IOError as inst:
             if inst.errno != 0:
                 raise
             self.close()
             raise IOError(errno.EPIPE, 'Broken pipe')
 
     def flush(self):
         try:
             return self.fp.flush()
         except IOError as inst:
             if inst.errno != errno.EINVAL:
                 raise
             self.close()
             raise IOError(errno.EPIPE, 'Broken pipe')
 
 def _is_win_9x():
     '''return true if run on windows 95, 98 or me.'''
     try:
         return sys.getwindowsversion()[3] == 1
     except AttributeError:
         return 'command' in encoding.environ.get('comspec', '')
 
 def openhardlinks():
     return not _is_win_9x()
 
 def parsepatchoutput(output_line):
     """parses the output produced by patch and returns the filename"""
     pf = output_line[14:]
     if pf[0] == '`':
         pf = pf[1:-1] # Remove the quotes
     return pf
 
 def sshargs(sshcmd, host, user, port):
     '''Build argument list for ssh or Plink'''
     pflag = 'plink' in sshcmd.lower() and '-P' or '-p'
     args = user and ("%s@%s" % (user, host)) or host
     return port and ("%s %s %s" % (args, pflag, port)) or args
 
 def setflags(f, l, x):
     pass
 
 def copymode(src, dst, mode=None):
     pass
 
 def checkexec(path):
     return False
 
 def checklink(path):
     return False
 
 def setbinary(fd):
     # When run without console, pipes may expose invalid
     # fileno(), usually set to -1.
     fno = getattr(fd, 'fileno', None)
     if fno is not None and fno() >= 0:
         msvcrt.setmode(fno(), os.O_BINARY)
 
 def pconvert(path):
     return path.replace(pycompat.ossep, '/')
 
 def localpath(path):
     return path.replace('/', '\\')
 
 def normpath(path):
     return pconvert(os.path.normpath(path))
 
 def normcase(path):
     return encoding.upper(path) # NTFS compares via upper()
 
 # see posix.py for definitions
 normcasespec = encoding.normcasespecs.upper
 normcasefallback = encoding.upperfallback
 
 def samestat(s1, s2):
     return False
 
 # A sequence of backslashes is special iff it precedes a double quote:
 # - if there's an even number of backslashes, the double quote is not
 #   quoted (i.e. it ends the quoted region)
 # - if there's an odd number of backslashes, the double quote is quoted
 # - in both cases, every pair of backslashes is unquoted into a single
 #   backslash
 # (See http://msdn2.microsoft.com/en-us/library/a1y7w461.aspx )
 # So, to quote a string, we must surround it in double quotes, double
 # the number of backslashes that precede double quotes and add another
 # backslash before every double quote (being careful with the double
 # quote we've appended to the end)
 _quotere = None
 _needsshellquote = None
 def shellquote(s):
     r"""
     >>> shellquote(r'C:\Users\xyz')
     '"C:\\Users\\xyz"'
     >>> shellquote(r'C:\Users\xyz/mixed')
     '"C:\\Users\\xyz/mixed"'
     >>> # Would be safe not to quote too, since it is all double backslashes
     >>> shellquote(r'C:\\Users\\xyz')
     '"C:\\\\Users\\\\xyz"'
     >>> # But this must be quoted
     >>> shellquote(r'C:\\Users\\xyz/abc')
     '"C:\\\\Users\\\\xyz/abc"'
     """
     global _quotere
     if _quotere is None:
         _quotere = re.compile(r'(\\*)("|\\$)')
     global _needsshellquote
     if _needsshellquote is None:
         # ":" is also treated as "safe character", because it is used as a part
         # of path name on Windows.  "\" is also part of a path name, but isn't
         # safe because shlex.split() (kind of) treats it as an escape char and
         # drops it.  It will leave the next character, even if it is another
         # "\".
         _needsshellquote = re.compile(r'[^a-zA-Z0-9._:/-]').search
     if s and not _needsshellquote(s) and not _quotere.search(s):
         # "s" shouldn't have to be quoted
         return s
     return '"%s"' % _quotere.sub(r'\1\1\\\2', s)
 
 def quotecommand(cmd):
     """Build a command string suitable for os.popen* calls."""
     if sys.version_info < (2, 7, 1):
         # Python versions since 2.7.1 do this extra quoting themselves
         return '"' + cmd + '"'
     return cmd
 
 def popen(command, mode='r'):
     # Work around "popen spawned process may not write to stdout
     # under windows"
     # http://bugs.python.org/issue1366
     command += " 2> %s" % os.devnull
     return os.popen(quotecommand(command), mode)
 
 def explainexit(code):
     return _("exited with status %d") % code, code
 
 # if you change this stub into a real check, please try to implement the
 # username and groupname functions above, too.
 def isowner(st):
     return True
 
 def findexe(command):
     '''Find executable for command searching like cmd.exe does.
     If command is a basename then PATH is searched for command.
     PATH isn't searched if command is an absolute or relative path.
     An extension from PATHEXT is found and added if not present.
     If command isn't found None is returned.'''
     pathext = encoding.environ.get('PATHEXT', '.COM;.EXE;.BAT;.CMD')
     pathexts = [ext for ext in pathext.lower().split(pycompat.ospathsep)]
     if os.path.splitext(command)[1].lower() in pathexts:
         pathexts = ['']
 
     def findexisting(pathcommand):
         'Will append extension (if needed) and return existing file'
         for ext in pathexts:
             executable = pathcommand + ext
             if os.path.exists(executable):
                 return executable
         return None
 
     if pycompat.ossep in command:
         return findexisting(command)
 
     for path in encoding.environ.get('PATH', '').split(pycompat.ospathsep):
         executable = findexisting(os.path.join(path, command))
         if executable is not None:
             return executable
     return findexisting(os.path.expanduser(os.path.expandvars(command)))
 
 _wantedkinds = set([stat.S_IFREG, stat.S_IFLNK])
 
 def statfiles(files):
     '''Stat each file in files. Yield each stat, or None if a file
     does not exist or has a type we don't care about.
 
     Cluster and cache stat per directory to minimize number of OS stat calls.'''
     dircache = {} # dirname -> filename -> status | None if file does not exist
     getkind = stat.S_IFMT
     for nf in files:
         nf  = normcase(nf)
         dir, base = os.path.split(nf)
         if not dir:
             dir = '.'
         cache = dircache.get(dir, None)
         if cache is None:
             try:
                 dmap = dict([(normcase(n), s)
                              for n, k, s in osutil.listdir(dir, True)
                              if getkind(s.st_mode) in _wantedkinds])
             except OSError as err:
                 # Python >= 2.5 returns ENOENT and adds winerror field
                 # EINVAL is raised if dir is not a directory.
                 if err.errno not in (errno.ENOENT, errno.EINVAL,
                                      errno.ENOTDIR):
                     raise
                 dmap = {}
             cache = dircache.setdefault(dir, dmap)
         yield cache.get(base, None)
 
 def username(uid=None):
     """Return the name of the user with the given uid.
 
     If uid is None, return the name of the current user."""
     return None
 
 def groupname(gid=None):
     """Return the name of the group with the given gid.
 
     If gid is None, return the name of the current group."""
     return None
 
 def removedirs(name):
     """special version of os.removedirs that does not remove symlinked
     directories or junction points if they actually contain files"""
     if osutil.listdir(name):
         return
     os.rmdir(name)
     head, tail = os.path.split(name)
     if not tail:
         head, tail = os.path.split(head)
     while head and tail:
         try:
             if osutil.listdir(head):
                 return
             os.rmdir(head)
         except (ValueError, OSError):
             break
         head, tail = os.path.split(head)
 
 def rename(src, dst):
     '''atomically rename file src to dst, replacing dst if it exists'''
     try:
         os.rename(src, dst)
     except OSError as e:
         if e.errno != errno.EEXIST:
             raise
         unlink(dst)
         os.rename(src, dst)
 
 def gethgcmd():
     return [sys.executable] + sys.argv[:1]
 
 def groupmembers(name):
     # Don't support groups on Windows for now
     raise KeyError
 
 def isexec(f):
     return False
 
 class cachestat(object):
     def __init__(self, path):
         pass
 
     def cacheable(self):
         return False
 
 def lookupreg(key, valname=None, scope=None):
     ''' Look up a key/value name in the Windows registry.
 
     valname: value name. If unspecified, the default value for the key
     is used.
     scope: optionally specify scope for registry lookup, this can be
     a sequence of scopes to look up in order. Default (CURRENT_USER,
     LOCAL_MACHINE).
     '''
     if scope is None:
         scope = (winreg.HKEY_CURRENT_USER, winreg.HKEY_LOCAL_MACHINE)
     elif not isinstance(scope, (list, tuple)):
         scope = (scope,)
     for s in scope:
         try:
             val = winreg.QueryValueEx(winreg.OpenKey(s, key), valname)[0]
             # never let a Unicode string escape into the wild
             return encoding.unitolocal(val)
         except EnvironmentError:
             pass
 
 expandglobs = True
 
 def statislink(st):
     '''check whether a stat result is a symlink'''
     return False
 
 def statisexec(st):
     '''check whether a stat result is an executable file'''
     return False
 
 def poll(fds):
     # see posix.py for description
     raise NotImplementedError()
 
 def readpipe(pipe):
     """Read all available data from a pipe."""
     chunks = []
     while True:
         size = win32.peekpipe(pipe)
         if not size:
             break
 
         s = pipe.read(size)
         if not s:
             break
         chunks.append(s)
 
     return ''.join(chunks)
 
 def bindunixsocket(sock, path):
     raise NotImplementedError('unsupported platform')