view mercurial/txnutil.py @ 46325:e5e6282fa66a

hghave: split apart testing for the curses module and `tic` executable

ef771d329961 skipped the check for the `tic` executable, because the curses
module alone on Windows is enough to pass the `test-*-curses.t` tests.  However,
`test-status-color.t` uses this same check and explicitly invoked the
executable, which fails on Windows.  From the cursory searching I did, curses on
unix requires `tic`, which I assume is why they were tied together in the first
place.  So this continues to require both to get past the curses guards on non
Windows platforms.

Differential Revision: https://phab.mercurial-scm.org/D9814

# 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(b'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(b'%s.pending' % filename, **kwargs), True)
        except IOError as inst:
            if inst.errno != errno.ENOENT:
                raise
    return (vfs(filename, **kwargs), False)