view mercurial/txnutil.py @ 40039:a0c18b271ea1

treemanifests: store whether a lazydirs entry needs copied after materializing

Due to the way that things like manifestlog.get caches its values, without
making a copy (if necessary) after calling readsubtree(), we might end up
adjusting the state of the same object on different contexts, breaking things
like dirty state tracking (and probably other things).

Differential Revision: https://phab.mercurial-scm.org/D4874

# 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)