mercurial/policy.py

progress: retry ferr.flush() and .write() on EINTR (issue5532)

See the inline comment how this could mitigate the issue.

I couldn't reproduce the exact problem on my Linux machine, but there are
at least two people who got EINTR in progress.py, and it seems file_write()
of Python 2 is fundamentally broken [1]. Let's make something in on 4.2.

 [1]: https://hg.python.org/cpython/file/v2.7.13/Objects/fileobject.c#l1850

# 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 = b'c'
policynoc = (b'cffi', b'cffi-allow', b'py')
policynocffi = (b'c', b'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 = b'py'

# Environment variable can always force settings.
if sys.version_info[0] >= 3:
    if 'HGMODULEPOLICY' in os.environ:
        policy = os.environ['HGMODULEPOLICY'].encode('utf-8')
else:
    policy = os.environ.get('HGMODULEPOLICY', policy)