policy: extend API version checks for cffi

This is just a stub for future extension. I could add a version constant to
CFFI modules by putting it to both ffi.set_source() and ffi.cdef(), but that
doesn't seem right. So for now, cffi modules will be explicitly unversioned
(i.e. version constant must be undefined or set to None.) We can revisit it
later when we need to consider CFFI support more seriously.

mercurial/policy.py

@@ -1,106 +1,106 b''
 # 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, fall back to the pure modules so the in-place build can
 # run without recompiling the C extensions. This will be overridden by
 # __modulepolicy__ generated by setup.py.
 policy = b'allow'
 policynoc = (b'cffi', b'cffi-allow', b'py')
 policynocffi = (b'c', b'py')
 _packageprefs = {
     # policy: (versioned package, pure package)
     b'c': (r'cext', None),
     b'allow': (r'cext', r'pure'),
     b'cffi': (None, r'pure'),  # TODO: (r'cffi', None)
     b'cffi-allow': (None, r'pure'),  # TODO: (r'cffi', r'pure')
     b'py': (None, r'pure'),
 }
 
 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 r'__pypy__' in sys.builtin_module_names:
     policy = b'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 r'HGMODULEPOLICY' in os.environ:
         policy = os.environ[r'HGMODULEPOLICY'].encode(r'utf-8')
 else:
     policy = os.environ.get(r'HGMODULEPOLICY', policy)
 
 def _importfrom(pkgname, modname):
     # from .<pkgname> import <modname> (where . is looked through this module)
     fakelocals = {}
     pkg = __import__(pkgname, globals(), fakelocals, [modname], level=1)
     try:
         fakelocals[modname] = mod = getattr(pkg, modname)
     except AttributeError:
         raise ImportError(r'cannot import name %s' % modname)
     # force import; fakelocals[modname] may be replaced with the real module
     getattr(mod, r'__doc__', None)
     return fakelocals[modname]
 
 # keep in sync with "version" in C modules
 _cextversions = {
-    r'base85': 1,
-    r'bdiff': 1,
-    r'diffhelpers': 1,
-    r'mpatch': 1,
-    r'osutil': 1,
-    r'parsers': 1,
+    (r'cext', r'base85'): 1,
+    (r'cext', r'bdiff'): 1,
+    (r'cext', r'diffhelpers'): 1,
+    (r'cext', r'mpatch'): 1,
+    (r'cext', r'osutil'): 1,
+    (r'cext', r'parsers'): 1,
 }
 
 def _checkmod(pkgname, modname, mod):
-    expected = _cextversions.get(modname)
+    expected = _cextversions.get((pkgname, modname))
     actual = getattr(mod, r'version', None)
     if actual != expected:
         raise ImportError(r'cannot import module %s.%s '
                           r'(expected version: %d, actual: %r)'
                           % (pkgname, modname, expected, actual))
 
 def importmod(modname):
     """Import module according to policy and check API version"""
     try:
         verpkg, purepkg = _packageprefs[policy]
     except KeyError:
         raise ImportError(r'invalid HGMODULEPOLICY %r' % policy)
     assert verpkg or purepkg
     if verpkg:
         try:
             mod = _importfrom(verpkg, modname)
             _checkmod(verpkg, modname, mod)
             return mod
         except ImportError:
             if not purepkg:
                 raise
     return _importfrom(purepkg, modname)