mercurial/policy.py

wireproto: unescape argument names in batch command (BC)

Clients escape both argument names and values when using the
batch command. Yet the server was only unescaping argument values.

Fortunately we don't have any argument names that need escaped. But
that isn't an excuse to lack symmetry in the code.

Since the server wasn't properly unescaping argument names, this
means we can never introduce an argument to a batchable command that
needs escaped because an old server wouldn't properly decode its name.
So we've introduced an assertion to detect the accidental introduction
of this in the future. Of course, we could introduce a server
capability that says the server knows how to decode argument names and
allow special argument names to go through. But until there is a need
for it (which I doubt there will be), we shouldn't bother with adding
an unused capability.

# policy.py - module policy logic for Mercurial.
#
# Copyright 2015 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.

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)