mercurial/txnutil.py

blackbox: resurrect recursion guard

If I added ui.log() to hg.repository() function, test-merge-subrepos.t
exploded. The problem is that the blackbox may create new repository instance
while logging is active, and the created repository owns its new ui derived
from the baseui, not from the ui which is processing the active logging.

I tried to work around the issue in ui.log(), but that turned out to be not
easy. We shouldn't globally lock the ui.log() since there may be more than
one active repo/ui instances in threaded environment. We could store the
logging state in thread-local storage, but that seems unnecessarily complex.
So this patch reintroduces the _inlog flag to per-repository logger instances.

# txnutil.py - transaction related utilities
#
#  Copyright FUJIWARA Katsunori <[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

from . import (
    encoding,
)

def mayhavepending(root):
    '''return whether 'root' may have pending changes, which are
    visible to this process.
    '''
    return root == encoding.environ.get('HG_PENDING')

def trypending(root, vfs, filename, **kwargs):
    '''Open  file to be read according to HG_PENDING environment variable

    This opens '.pending' of specified 'filename' only when HG_PENDING
    is equal to 'root'.

    This returns '(fp, is_pending_opened)' tuple.
    '''
    if mayhavepending(root):
        try:
            return (vfs('%s.pending' % filename, **kwargs), True)
        except IOError as inst:
            if inst.errno != errno.ENOENT:
                raise
    return (vfs(filename, **kwargs), False)