functools.cached_property and property swallows AttributeError raised during property computation when the class has __getattr__, causing silent failures.

[PcdPanda]

Bug report

Bug description:

Minimal Reproduction

from functools import cached_property

class Example:
  @cached_property
  def data(self):
      return None.some_attribute  # Raises AttributeError

  def __getattr__(self, name):
      return "FALLBACK"

obj = Example()
print(obj.data)  # Expected: AttributeError, Got: "FALLBACK"

Expected Behavior

AttributeError should be raised: 'NoneType' object has no attribute 'some_attribute'

Actual Behavior

Returns "FALLBACK" (from getattr)

Impact

• hasattr(obj, 'data') returns True (wrong)
• getattr(obj, 'data', 'DEFAULT') returns "FALLBACK" instead of 'DEFAULT'
• Silent failures instead of fast failures
• Difficult to debug

Root Cause

Python's descriptor protocol treats AttributeError from get as "attribute doesn't exist", triggering getattr fallback.

Python Versions

• Tested: 3.13

Workaround

Don't use @cached_property with classes that have getattr, or manually wrap exceptions.

Proposal

Add a ignore_error parameters to cached_property and property

CPython versions tested on:

CPython main branch, 3.13

Operating systems tested on:

Linux

[picnixz]

This is not a restriction to @cached_property. This would also happen with @property and this is the regular behavior when accessing a member raises AttributeError. We always delegate to __getattr__.

class Example:
  @property
  def data(self):
      raise AttributeError
  def __getattr__(self, name):
      return "FALLBACK"

assert Example().data == "FALLBACK"