view mercurial/txnutil.py @ 41279:c9e1104e6272

exthelper: drop the addattr() decorator

Yuya pointed out that this goes against the typical advice to not add attributes
to classes[1].  The evolve extension still uses this a handful of times, so
maybe it should be brought back in the future if a general use is found.  But it
isn't nice to have a new helper API that can lead to easy problems.

[1] https://www.mercurial-scm.org/pipermail/mercurial-devel/2018-December/126330.html

# 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)