[issue39865] getattr silences an unrelated AttributeError

[pasenor]

New submission from pasenor <gosha at fro.lv>:

if a class has a descriptor and a defined __getattr__ method, and an AttributeError (unrelated to the descriptor lookup) is raised inside the descriptor, it will be silenced:

class A:
    @property
    def myprop(self):
        print("property called")
        a = 1
        a.foo  # <-- AttributeError that should not be silenced

    def __getattr__(self, attr_name):
        print("__getattr__ called")

a = A()
a.myprop


In this example myprop() is called, the error silenced, then __getattr__() is called.
This can lead to rather subtle bugs. Probably an explicit AttributeError should be raised instead.

----------
messages: 363449
nosy: pasenor
priority: normal
severity: normal
status: open
title: getattr silences an unrelated AttributeError
versions: Python 2.7, Python 3.5, 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/issue39865>
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