view mercurial/txnutil.py @ 39644:3b421154d2ca

py3: fix str vs bytes in enough places to run `hg version` on Windows

I don't have Visual Studio 2015 at home, but this now works with a handful of
extensions (blackbox, extdiff, patchbomb, phabricator and rebase, but not
evolve):

    $ HGMODULEPOLICY=py py -3 ../hg version

Enabling the evolve extension causes the usual "failed to import ..." line, but
then print this before the usual version output:

    ('commit', '[b'debugancestor', b'debugapplystreamclonebundle', ...,
     b'verify', b'version']')

... where the elided part seems to be every command and alias known.

# 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)