mercurial/txnutil.py

obsolete: make sure windows tests pass when stat() is given a URL

This is a temporary fix for an issue that's only visible on windows, but exists
on other platforms as well.

The issue is if we're trying to use obsstore from a remote peer and that peer
is a static HTTP repo, vfs tries to os.stat() a remote file using a URL to that
file (e.g. http://localhost/repo/.hg/store/obsstore). The next patch in this
series makes branchcache obsolescence-aware, so in certain situations exchange
process will try os.stat()ing a URL. On windows this will produce an OSError
that is not ENOENT, but EINVAL instead (because of `:` symbol, for example).

Differential Revision: https://phab.mercurial-scm.org/D12100

# 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(b'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(b'%s.pending' % filename, **kwargs), True)
        except IOError as inst:
            if inst.errno != errno.ENOENT:
                raise
    return (vfs(filename, **kwargs), False)