mercurial/thirdparty/zope/interface/_flatten.py

thirdparty: port zope.interface to relative imports

By using relative imports, we're guaranteed to get modules
vendored with Mercurial rather than other random modules
that might be in sys.path.

My editor strips trailing whitespace on save. So some minor
source code cleanup was also performed as part of this commit.

# no-check-commit because some modified lines have double newlines

Differential Revision: https://phab.mercurial-scm.org/D2930

##############################################################################
#
# Copyright (c) 2002 Zope Foundation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
##############################################################################
"""Adapter-style interface registry

See Adapter class.
"""

from __future__ import absolute_import

from .interface import Declaration

def _flatten(implements, include_None=0):

    try:
        r = implements.flattened()
    except AttributeError:
        if implements is None:
            r=()
        else:
            r = Declaration(implements).flattened()

    if not include_None:
        return r

    r = list(r)
    r.append(None)
    return r