view mercurial/txnutil.py @ 47683:284a20269a97

dirstate-v2: Separate iterators for dirfoldmap and debugdirstate

`dirstatemap.dirfoldmap` was recently changed to re-use a Rust iterator
that was added for the `hg debugdirstate` command.

That iterator was based on all nodes in the tree dirstate without an entry
only existing to hold child nodes, and therefore being directories.
However to optimize status further we may want to store additional nodes
for unknown or ignored files and directories. At that point the two users
of this iterator will want different things, so let’s make two iterators
instead.

See doc-comments in `dispatch.rs`.

Differential Revision: https://phab.mercurial-scm.org/D11099

# 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)