mercurial: be more strict about loading dual implemented modules
With this change in place, we should have slightly stronger guarantees
about how modules with both Python and C implementations are loaded.
Before, our module loader's default policy looked under both mercurial/*
and mercurial/pure/* and imported whatever it found, C or pure. The fact
it looked in both locations by default was a temporary regression from
the beginning of this series.
This patch does 2 things:
1) Changes the default module load policy to only load C modules
2) Verifies that files loaded from mercurial/* are actually C modules
This 2nd behavior change makes our new module loading mechanism
stricter than from before this series. Before, it was possible to load
a .py-based module from mercurial/*. This could happen if an old
installation orphaned a file and then somehow didn't install the C
version for the new install. We now detect this odd configuration
and fall back to loading the pure Python module, assuming it is
allowed. In the case of a busted installation, we fail fast. While
we could fall back, we explicitly decide not to do this because
we don't want people accidentally not running the C modules and having
slow performance as a result.
--- a/mercurial/__init__.py Thu Dec 03 21:48:12 2015 -0800
+++ b/mercurial/__init__.py Tue Nov 24 22:50:04 2015 -0800
@@ -22,8 +22,7 @@
# By default, require the C extensions for performance reasons.
if modulepolicy == '@' 'MODULELOADPOLICY' '@':
- # TODO change to 'c' once installer is changed.
- modulepolicy = 'allow'
+ modulepolicy = 'c'
# Environment variable can always force settings.
modulepolicy = os.environ.get('HGMODULEPOLICY', modulepolicy)
@@ -79,11 +78,9 @@
# mercurial/* are C extensions. If the current policy allows the
# loading of .py modules, the module will be re-imported from
# mercurial/pure/* below.
- # TODO uncomment once setup.py is updated to actually install
- # into mercurial/pure.
- #if modinfo[2][2] != imp.C_EXTENSION:
- # raise ImportError('.py version of %s found where C '
- # 'version should exist' % name)
+ if modinfo[2][2] != imp.C_EXTENSION:
+ raise ImportError('.py version of %s found where C '
+ 'version should exist' % name)
except ImportError:
if modulepolicy == 'c':