mercurial/txnutil.py

ui: move request exit handlers to global state

Since the ui objects can be created with the 'load' class method, it
is possible to lose the exit handlers information from the old ui instance. For
example, running 'test-bad-extension.t' leads to this situation where chg
creates a new ui instance which does not copy the exit handlers from the
earlier ui instance. For exit handlers, which are special cases anyways, it
probably makes sense to have a global state of the handlers. This would ensure
that the exit handlers registered once are definitely executed at the end of
the request.

Test Plan:
Ran all the tests without '--chg' option. This also fixes the
'test-bad-extension.t' with the '--chg' option.

Differential Revision: https://phab.mercurial-scm.org/D1166

# 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)