view hgext/narrow/narrowrepo.py @ 45047:40120de810ba stable

demandimport: ignore `lzma` module for demandimport

This makes importing the module fail if the `_lzma` module is not present.

This makes e.g. tarfile correctly recognize if LZMA support is not present. It
changes the exception

    File "/usr/lib/python3.6/tarfile.py", line 1694, in xzopen
      fileobj = lzma.LZMAFile(fileobj or name, mode, preset=preset)
  AttributeError: module 'lzma' has no attribute 'LZMAFile'

to the more correct exception

    File "/usr/lib/python3.6/tarfile.py", line 1692, in xzopen
      raise CompressionError("lzma module is not available")
  tarfile.CompressionError: lzma module is not available

Also, it prevents that the error "abort: No module named '_lzma'!" is shown when
a development warning is to be shown. The reason why that happened is that for
showing the warning, we get information about the stack frames from the inspect
module, which accesses the `__file__` attribute of all modules in `sys.modules`
to build some cache, causing all modules (including `lzma`) to be imported.

# narrowrepo.py - repository which supports narrow revlogs, lazy loading
#
# Copyright 2017 Google, Inc.
#
# 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

from mercurial import wireprototypes

from . import narrowdirstate


def wraprepo(repo):
    """Enables narrow clone functionality on a single local repository."""

    class narrowrepository(repo.__class__):
        def _makedirstate(self):
            dirstate = super(narrowrepository, self)._makedirstate()
            return narrowdirstate.wrapdirstate(self, dirstate)

        def peer(self):
            peer = super(narrowrepository, self).peer()
            peer._caps.add(wireprototypes.NARROWCAP)
            peer._caps.add(wireprototypes.ELLIPSESCAP)
            return peer

    repo.__class__ = narrowrepository