mercurial/interfaces/util.py

rust-index: add a function to convert PyObject index for hg-core

Function in hg-core need something implementing the `Graph` trait. Right now,
the `hg-cpython` entry points directly turn the PyObject passed as argument
into a `cindex::Index`. However, if we start having the option to use an Index
in Rust, we need to dispatch between the different possible PyObject we could
receive.

So move the "duplicate" call into a unified function. When time come. It will be
easy to update the logic of all interface when the time come.

Differential Revision: https://phab.mercurial-scm.org/D7653

# util.py - Utilities for declaring interfaces.
#
# Copyright 2018 Gregory Szorc <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

# zope.interface imposes a run-time cost due to module import overhead and
# bookkeeping for declaring interfaces. So, we use stubs for various
# zope.interface primitives unless instructed otherwise.

from __future__ import absolute_import

from .. import encoding

if encoding.environ.get(b'HGREALINTERFACES'):
    from ..thirdparty.zope import interface as zi

    Attribute = zi.Attribute
    Interface = zi.Interface
    implementer = zi.implementer
else:

    class Attribute(object):
        def __init__(self, __name__, __doc__=b''):
            pass

    class Interface(object):
        def __init__(
            self, name, bases=(), attrs=None, __doc__=None, __module__=None
        ):
            pass

    def implementer(*ifaces):
        def wrapper(cls):
            return cls

        return wrapper