Bug report
I noticed recently that Setuptools CI started failing for Python 3.12.0a7 with a SystemError that is difficult to understand:
SystemError: <built-in method startswith of str object at 0x7fe399991298> returned a result with an exception set
At a first glance this error does not make much sense because str.startswith is a built-in method in a built-in data structure. I am struggling to see how it can have an exception set attached to the result.
I managed to create the following simplified reproducer:
docker run --rm -it python:3.12.0a7-bullseye
Python 3.12.0a7 (main, Apr 12 2023, 14:13:09) [GCC 10.2.1 20210110] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> class Distribution:
... @property
... def version(self):
... try:
... return self._version
... except AttributeError as e:
... # ... complex code omitted for the sake of simplification ...
... raise ValueError("Missing Version")
... def __getattr__(self, attr):
... if attr.startswith("_"):
... raise AttributeError(attr)
... # ... complex code omitted for the sake of simplification ...
... return 42
...
>>> dist = Distribution()
>>> dist.version
Traceback (most recent call last):
File "<stdin>", line 5, in version
File "<stdin>", line 11, in __getattr__
AttributeError: _version. Did you mean: 'version'?
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "<stdin>", line 8, in version
ValueError: Missing Version
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 10, in __getattr__
SystemError: <method 'startswith' of 'str' objects> returned a result with an exception set
>>>The error seems to be related to the combination of the following factors:
- A
property is being used1
- The property getter access an undefined attribute and triggers
__getattr__
__getattr__ raises an AttributeError- The property getter is supposed to catch the
AttributeError exception and raise a different exeception.
My expectation is that the SystemError never gets triggered with the confusing message. Instead the example should end up with a ValueError.
Please note that the example is very simplified. For the realistic implementation please consider pkg_resources.Distribution.
Your environment
- CPython versions tested on: 3.12.0a7
- Operating system and architecture:
Reproducer tested on both Ubuntu 20.04.6 LTS machine and python:3.12.0a7-bullseye container
Problem also identified in GitHub Actions runners: ubuntu-latest, macos-latest, windows-latest (see https://github.com/pypa/setuptools/actions/runs/4710601389?pr=3893) for Python 3.12-dev.
Bug report
I noticed recently that Setuptools CI started failing for Python 3.12.0a7 with a
SystemErrorthat is difficult to understand:At a first glance this error does not make much sense because
str.startswithis a built-in method in a built-in data structure. I am struggling to see how it can have an exception set attached to the result.I managed to create the following simplified reproducer:
The error seems to be related to the combination of the following factors:
propertyis being used1__getattr____getattr__raises anAttributeErrorAttributeErrorexception and raise a different exeception.My expectation is that the
SystemErrornever gets triggered with the confusing message. Instead the example should end up with aValueError.Please note that the example is very simplified. For the realistic implementation please consider
pkg_resources.Distribution.Your environment
Reproducer tested on both Ubuntu 20.04.6 LTS machine and
python:3.12.0a7-bullseyecontainerProblem also identified in GitHub Actions runners:
ubuntu-latest,macos-latest,windows-latest(see https://github.com/pypa/setuptools/actions/runs/4710601389?pr=3893) for Python3.12-dev.Footnotes
If we replace the property with a regular method, the example works as expected. ↩