view mercurial/thirdparty/zope/interface/_flatten.py @ 37179:49630e75635d

thirdparty: allow zope.interface.advice to be lazily imported

The symbol from this module is only used in functions. Let's access
that symbol through its imported module so importing
zope.interface.advice can be lazy.

Differential Revision: https://phab.mercurial-scm.org/D2931

##############################################################################
#
# 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