mercurial/dirstateguard.py

tests: correct (I think) command in test-largefiles-update

When this test was introduced, it used the short-form of all the flags
on this update invocation. I suspect, based on the "start with clean
dirstates" comment and the fact that the no-exec branch of the #if
guard leaves dirstate clean, that this should have been 'update -qCr'
instead of 'update -qcr', but that a bug in largefiles --check
handling left this problem unnoticed.

I'll leave a breadcrumb further up about the current failure mode in
the hopes that we can fix this some day.

This was previously discussed in [0] but the trail in that thread goes
cold after a few replies. Given that this is still a flaky test, that
appears to only be passing by bad fortune, I think it's worth
correcting the code of the test to make a correct assertion, and to
keep track of the suspected bug with some other mechanism than an
invalid test (if we had support for "expected failure" blocks this
might be a worthwhile use of them?).

0: https://www.mercurial-scm.org/pipermail/mercurial-devel/2016-October/089501.html

# 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,
)

class dirstateguard(object):
    '''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._suffix = '.backup.%s.%d' % (name, id(self))
        repo.dirstate.savebackup(repo.currenttransaction(), self._suffix)
        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: dirstate%s")
                   % self._suffix)
            raise error.Abort(msg)

        self._repo.dirstate.clearbackup(self._repo.currenttransaction(),
                                         self._suffix)
        self._active = False
        self._closed = True

    def _abort(self):
        self._repo.dirstate.restorebackup(self._repo.currenttransaction(),
                                           self._suffix)
        self._active = False

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