view mercurial/txnutil.py @ 35983:f540b6448738

largefiles: register wire protocol commands with modern APIs

The wireproto.wireprotocommand decorator is the preferred mechanism for
registering wire protocol commands. In addition, wireproto.commands
is no longer a 2-tuple and use of that 2-tuple API should be considered
deprecated.

This commit ports largefiles to use wireproto.wireprotocommand()
and ports to the "commandentry" API.

As part of this, the definition of the "lheads" wire protocol
command is moved to the proper stanza.

We stop short of actually using wireprotocommand as a decorator
in order to minimize churn. We should ideally move wire protocol
commands to the registrar mechanism. But that's for another
changeset.

Differential Revision: https://phab.mercurial-scm.org/D2018

# 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)