[issue45985] AttributeError from @property inadvertantly flows into __getattr__

[Ofer Koren]

New submission from Ofer Koren <koreno at gmail.com>:

There's For quite a long time I've been seeing this bug:

>>> class A():

...     @property
...     def foo(self):
...         return self.bar  # <---- this is where it all starts ('bar' isn't found)
... 
...     def __getattr__(self, attr):
...         raise AttributeError(attr)  # <--- let's pretend our getattr couldn't find the attr


>>> A().foo


Traceback (most recent call last):
  File "t.py", line 13, in <module>
    A().foo
  File "t.py", line 10, in __getattr__
    raise AttributeError(attr)
AttributeError: foo


So an AttributeError spawned by `self.bar` caused us to "fallback" on __getattr__ with attr='foo', leading the naive code there to produce a very confusing error message.


My workaround was to use a @safe_property decorator, one that catches AttributeError exceptions and converts them to RuntimeErrors instead, so that they don't flow into the unsuspecting __getattr__.
I believe python should adopt this behavior into the built-in property decorator, perhaps with a more appropriate exception type.

----------
messages: 407701
nosy: koreno
priority: normal
severity: normal
status: open
title: AttributeError from @property inadvertantly flows into __getattr__
type: behavior
versions: Python 3.10, Python 3.11, Python 3.6, Python 3.7, Python 3.8, Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue45985>
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