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# policy.py - module policy logic for Mercurial.
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#
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# Copyright 2015 Gregory Szorc <gregory.szorc@gmail.com>
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#
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# This software may be used and distributed according to the terms of the
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# GNU General Public License version 2 or any later version.
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from __future__ import absolute_import
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import os
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import sys
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# Rules for how modules can be loaded. Values are:
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#
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# c - require C extensions
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# allow - allow pure Python implementation when C loading fails
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# cffi - required cffi versions (implemented within pure module)
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# cffi-allow - allow pure Python implementation if cffi version is missing
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# py - only load pure Python modules
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#
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# By default, fall back to the pure modules so the in-place build can
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# run without recompiling the C extensions. This will be overridden by
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# __modulepolicy__ generated by setup.py.
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policy = b'allow'
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_packageprefs = {
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# policy: (versioned package, pure package)
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b'c': (r'cext', None),
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b'allow': (r'cext', r'pure'),
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b'cffi': (r'cffi', None),
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b'cffi-allow': (r'cffi', r'pure'),
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b'py': (None, r'pure'),
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}
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try:
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from . import __modulepolicy__
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policy = __modulepolicy__.modulepolicy
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except ImportError:
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pass
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# PyPy doesn't load C extensions.
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#
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# The canonical way to do this is to test platform.python_implementation().
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# But we don't import platform and don't bloat for it here.
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if r'__pypy__' in sys.builtin_module_names:
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policy = b'cffi'
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# Environment variable can always force settings.
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if sys.version_info[0] >= 3:
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if r'HGMODULEPOLICY' in os.environ:
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policy = os.environ[r'HGMODULEPOLICY'].encode(r'utf-8')
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else:
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policy = os.environ.get(r'HGMODULEPOLICY', policy)
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def _importfrom(pkgname, modname):
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# from .<pkgname> import <modname> (where . is looked through this module)
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fakelocals = {}
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pkg = __import__(pkgname, globals(), fakelocals, [modname], level=1)
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try:
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fakelocals[modname] = mod = getattr(pkg, modname)
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except AttributeError:
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raise ImportError(r'cannot import name %s' % modname)
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# force import; fakelocals[modname] may be replaced with the real module
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getattr(mod, r'__doc__', None)
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return fakelocals[modname]
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# keep in sync with "version" in C modules
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_cextversions = {
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(r'cext', r'base85'): 1,
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(r'cext', r'bdiff'): 3,
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(r'cext', r'mpatch'): 1,
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(r'cext', r'osutil'): 4,
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(r'cext', r'parsers'): 6,
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}
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# map import request to other package or module
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_modredirects = {
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(r'cext', r'charencode'): (r'cext', r'parsers'),
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(r'cffi', r'base85'): (r'pure', r'base85'),
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(r'cffi', r'charencode'): (r'pure', r'charencode'),
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(r'cffi', r'parsers'): (r'pure', r'parsers'),
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}
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def _checkmod(pkgname, modname, mod):
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expected = _cextversions.get((pkgname, modname))
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actual = getattr(mod, r'version', None)
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if actual != expected:
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raise ImportError(r'cannot import module %s.%s '
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r'(expected version: %d, actual: %r)'
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% (pkgname, modname, expected, actual))
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def importmod(modname):
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"""Import module according to policy and check API version"""
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try:
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verpkg, purepkg = _packageprefs[policy]
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except KeyError:
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raise ImportError(r'invalid HGMODULEPOLICY %r' % policy)
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assert verpkg or purepkg
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if verpkg:
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pn, mn = _modredirects.get((verpkg, modname), (verpkg, modname))
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try:
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mod = _importfrom(pn, mn)
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if pn == verpkg:
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_checkmod(pn, mn, mod)
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return mod
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except ImportError:
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if not purepkg:
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raise
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pn, mn = _modredirects.get((purepkg, modname), (purepkg, modname))
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return _importfrom(pn, mn)
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