view mercurial/policy.py @ 30306:5581b294f3c6

help: show help for disabled extensions (issue5228)

This patch does not exactly solve issue5228 but it results in a better
condition on this issue. For disabled extensions, we used to parse the
module and get the first occurrences of docstring and then return the first
line of that as an introductory heading of extension. This is what we get
today.

This patch returns the whole docstring of the module as a help for extension,
which is more informative. There are some modules which don't have much
docstring at top level except the heading so those are unaffected by this
change. To follow the existing trend of showing commands either we have to
load the extension or have a very ugly parsing method which don't even assure
correctness.

# 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)