demandimport: support lazy loading for absolute_import
Before, we didn't support lazy loading if absolute_import was in
effect and a fromlist was used. This meant that "from . import X"
wasn't lazy and performance could suffer as a result.
With this patch, we now support lazy loading for this scenario.
As part of developing this, I discovered issues when module names
are defined. Since the enforced import style only allows
"from X import Y" or "from .X import Y" in very few scenarios
when absolute_import is enabled - scenarios where Y is not a
module and thus there is nothing to lazy load - I decided to drop
support for this case instead of chasing down the errors. I don't
think much harm will come from this. But I'd like to take another
look once all modules are using absolute_import and I can see the
full extent of what is using names in absolute_import mode.
--- a/mercurial/demandimport.py Sat Aug 08 17:07:34 2015 -0700
+++ b/mercurial/demandimport.py Sat Aug 08 16:13:27 2015 -0700
@@ -139,7 +139,24 @@
# so modern Mercurial code will have level >= 0.
if level >= 0:
- return _origimport(name, globals, locals, fromlist, level)
+ # Mercurial's enforced import style does not use
+ # "from a import b,c,d" or "from .a import b,c,d" syntax. In
+ # addition, this appears to be giving errors with some modules
+ # for unknown reasons. Since we shouldn't be using this syntax
+ # much, work around the problems.
+ if name:
+ return _hgextimport(_origimport, name, globals, locals,
+ fromlist, level)
+
+ mod = _hgextimport(_origimport, name, globals, locals, level=level)
+ for x in fromlist:
+ # Missing symbols mean they weren't defined in the module
+ # itself which means they are sub-modules.
+ if getattr(mod, x, nothing) is nothing:
+ setattr(mod, x,
+ _demandmod(x, mod.__dict__, locals, level=level))
+
+ return mod
# But, we still need to support lazy loading of standard library and 3rd
# party modules. So handle level == -1.