view mercurial/txnutil.py @ 39857:8dab7c8a93eb

upgrade: report size of backing files, not internal storage size

upgrade.py is the only consumer of filelog.index, which I'd like
to eliminate from the file storage interface.

This commit changes the upgrade code to report the storage size
of files by looking at the size of the files backing its storage
instead of looking at the index.

I'm not convinced the approach in this patch will live very long
because it is relying on low-level attributes like "opener" and
"files," which may behave very differently on non-revlog storage.
But the data is only used for reporting purposes and it does get
us one step closer to eliminating "index."

A side-effect of this change is we now report the size of the revlog
index data - not just the revision data. I think this is more
accurate.

Differential Revision: https://phab.mercurial-scm.org/D4717

# 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)