view mercurial/txnutil.py @ 34845:78d9a7b7cdb6

extensions: always include traceback when extension setup fails

I have spent a lot of time debugging extensions that failed to load
because we don't include a traceback and I didn't realize I could get
traceback for the extension failure with --traceback. Let's just turn
them on by default, since it should be rare that the user sees these
tracebacks anyway (and if they do, it's not so bad if the extra
traceback pushes them a little harder to report the problem).

Since we already had a test case with --traceback and one without, I
just removed the one with the flag.

Differential Revision: https://phab.mercurial-scm.org/D1164

# 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)