mercurial/txnutil.py

hgweb: add a sendtemplate() helper function

This pattern is common. Let's make a helper function to reduce
boilerplate.

We store the "global" template on the requestcontext instance and
use it. The templater used by the helper function is the same
templater that's passed in as an argument to the @webcommand
functions. It needs to be this way because various commands are
accessing and mutating the defaults on the templater instance.

Differential Revision: https://phab.mercurial-scm.org/D2799

# 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)