# policy.py - module policy logic for Mercurial.

#

# Copyright 2015 Gregory Szorc <gregory.szorc@gmail.com>

#

# 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 os

import sys

# Rules for how modules can be loaded. Values are:

#

#    c - require C extensions

#    allow - allow pure Python implementation when C loading fails

#    cffi - required cffi versions (implemented within pure module)

#    cffi-allow - allow pure Python implementation if cffi version is missing

#    py - only load pure Python modules

#

# By default, require the C extensions for performance reasons.

policy = 'c'

policynoc = ('cffi', 'cffi-allow', 'py')

policynocffi = ('c', 'py')

try:

    from . import __modulepolicy__

    policy = __modulepolicy__.modulepolicy

except ImportError:

    pass

# PyPy doesn't load C extensions.

#

# The canonical way to do this is to test platform.python_implementation().

# But we don't import platform and don't bloat for it here.

if '__pypy__' in sys.builtin_module_names:

    policy = 'cffi'

# Our C extensions aren't yet compatible with Python 3. So use pure Python

# on Python 3 for now.

if sys.version_info[0] >= 3:

    policy = 'py'

# Environment variable can always force settings.

policy = os.environ.get('HGMODULEPOLICY', policy)