mercurial/dirstateguard.py

setup: don't support py 3.5.0, 3.5.1, 3.5.2 because of bug in codecs

codecs.escape_encode() raises SystemError if an empty bytestring is passed. We
do that at some places in our code and because of this bug, things break.
Therefore we can't support the mentioned version. The bug was fixed in 3.5.3,
3.6.0 beta 2. We can't support 3.6.0 anyway because of bug in formatting
bytestrings.

Link to the python bug: https://bugs.python.org/issue25270

Differential Revision: https://phab.mercurial-scm.org/D4475

# dirstateguard.py - class to allow restoring dirstate after failure
#
# Copyright 2005-2007 Matt Mackall <[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

from .i18n import _

from . import (
    error,
    narrowspec,
    util,
)

class dirstateguard(util.transactional):
    '''Restore dirstate at unexpected failure.

    At the construction, this class does:

    - write current ``repo.dirstate`` out, and
    - save ``.hg/dirstate`` into the backup file

    This restores ``.hg/dirstate`` from backup file, if ``release()``
    is invoked before ``close()``.

    This just removes the backup file at ``close()`` before ``release()``.
    '''

    def __init__(self, repo, name):
        self._repo = repo
        self._active = False
        self._closed = False
        self._backupname = 'dirstate.backup.%s.%d' % (name, id(self))
        self._narrowspecbackupname = ('narrowspec.backup.%s.%d' %
                                      (name, id(self)))
        repo.dirstate.savebackup(repo.currenttransaction(), self._backupname)
        narrowspec.savebackup(repo, self._narrowspecbackupname)
        self._active = True

    def __del__(self):
        if self._active: # still active
            # this may occur, even if this class is used correctly:
            # for example, releasing other resources like transaction
            # may raise exception before ``dirstateguard.release`` in
            # ``release(tr, ....)``.
            self._abort()

    def close(self):
        if not self._active: # already inactivated
            msg = (_("can't close already inactivated backup: %s")
                   % self._backupname)
            raise error.Abort(msg)

        self._repo.dirstate.clearbackup(self._repo.currenttransaction(),
                                         self._backupname)
        narrowspec.clearbackup(self._repo, self._narrowspecbackupname)
        self._active = False
        self._closed = True

    def _abort(self):
        narrowspec.restorebackup(self._repo, self._narrowspecbackupname)
        self._repo.dirstate.restorebackup(self._repo.currenttransaction(),
                                           self._backupname)
        self._active = False

    def release(self):
        if not self._closed:
            if not self._active: # already inactivated
                msg = (_("can't release already inactivated backup: %s")
                       % self._backupname)
                raise error.Abort(msg)
            self._abort()