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gh-117182: Allow lazily loaded modules to modify their own __class__ #117185

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Merged
FFY00 merged 3 commits into from
Apr 9, 2024
Merged

gh-117182: Allow lazily loaded modules to modify their own __class__ #117185

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933c646
gh-117182: Test interaction between lazy modules and self-modifying m…
effigies Mar 23, 2024
a5e9670
gh-117182: Allow modules to modify their own __class__ when lazily lo…
effigies Mar 23, 2024
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effigies Mar 23, 2024
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gh-117182: Allow modules to modify their own __class__ when lazily lo… 
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@effigies
effigies committed Mar 29, 2024
commit a5e96703d96d78e93df67c748edcf05904bc23bc
12 changes: 8 additions & 4 deletions Lib/importlib/util.py
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Original file line number Diff line number Diff line change
Expand Up @@ -178,15 +178,17 @@ def __getattribute__(self, attr):
# Only the first thread to get the lock should trigger the load
# and reset the module's class. The rest can now getattr().
if object.__getattribute__(self, '__class__') is _LazyModule:
__class__ = loader_state['__class__']

# Reentrant calls from the same thread must be allowed to proceed without
# triggering the load again.
# exec_module() and self-referential imports are the primary ways this can
# happen, but in any case we must return something to avoid deadlock.
if loader_state['is_loading']:
return object.__getattribute__(self, attr)
return __class__.__getattribute__(self, attr)
loader_state['is_loading'] = True

__dict__ = object.__getattribute__(self, '__dict__')
__dict__ = __class__.__getattribute__(self, '__dict__')

# All module metadata must be gathered from __spec__ in order to avoid
# using mutated values.
Expand Down Expand Up @@ -216,8 +218,10 @@ def __getattribute__(self, attr):
# Update after loading since that's what would happen in an eager
# loading situation.
__dict__.update(attrs_updated)
# Finally, stop triggering this method.
self.__class__ = types.ModuleType
# Finally, stop triggering this method, if the module did not
# already update its own __class__.
if isinstance(self, _LazyModule):
object.__setattr__(self, '__class__', __class__)

return getattr(self, attr)

Expand Down