view mercurial/txnutil.py @ 31499:31d2ddfd338c

color: sync text attributes and buffered text output on Windows (issue5508)

I originally noticed that log output wasn't being colored after 3a4c0905f357,
but there were other complications too.  With a bunch of untracked files, only
the first 1K of characters were colored pink, and the rest were normal white.  A
single modified file at the top would also be colored pink.

Line buffering and full buffering are treated as the same thing in Windows [1],
meaning the stream is either buffered or not.  I can't find any explicit
documentation to say stdout is unbuffered by default when attached to a console
(but some internet postings indicated that is the case[2]).  Therefore, it seems
that explicit flushes are better than just not reopening stdout.

NB: pager is now on by default, and needs to be disabled to see any color on
Windows.

[1] https://msdn.microsoft.com/en-us/library/86cebhfs(v=vs.140).aspx
[2] https://sourceforge.net/p/mingw/mailman/message/27121137/

# 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)