René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Issues when showing broken `Exception.__notes__`","articleBody":"# Bug report\r\n\r\nWhen [notes on an exception](https://docs.python.org/3/library/exceptions.html#BaseException.__notes__) cannot be shown because the `repr` and `str` raise exceptions, a `\u003cnote str() failed\u003e` message is shown instead. In the case where `exception.__notes__` is not a sequence and cannot be shown, a `\u003c__notes__ repr() failed\u003e` is shown. In the second case, the message does not include a trailing newline.\r\n\r\n`__notes__` is a list containing a broken \"note\" - output includes a newline:\r\n```python\r\nclass A:\r\n    def __repr__(self):\r\n        raise Exception()\r\n\r\ne = Exception()\r\ne.__notes__ = [A()]  # !!!\r\nraise e\r\n```\r\n```\r\nuser@host $ ./repro.py\r\nTraceback (most recent call last):\r\n  File \"./repro.py\", line 8, in \u003cmodule\u003e\r\n    raise e\r\nException\r\n\u003cnote str() failed\u003e\r\nuser@host $ \r\n```\r\n\r\n`__notes__` is just a single broken \"note\" - output does not include a newline:\r\n```python\r\nclass A:\r\n    def __repr__(self):\r\n        raise Exception()\r\n\r\ne = Exception()\r\ne.__notes__ = A()  # !!!\r\nraise e\r\n```\r\n```\r\nuser@host $ ./repro.py\r\nTraceback (most recent call last):\r\n  File \"./repro.py\", line 8, in \u003cmodule\u003e\r\n    raise e\r\nException\r\n\u003c__notes__ repr() failed\u003euser@host $ \r\n```\r\n\r\nAdditionally, when `__notes__` is a string/bytes, the contents are expoded over multiple lines because of an `isinstance(__notes__, Sequence)` check.\r\n\r\nString:\r\n```python\r\ne = Exception()\r\ne.__notes__ = \"a note\"\r\nraise e\r\n```\r\n```\r\nuser@host $ ./repro.py\r\nTraceback (most recent call last):\r\n  File \"./repro.py\", line 8, in \u003cmodule\u003e\r\n    raise e\r\nException\r\na\r\n\r\nn\r\no\r\nt\r\ne\r\nuser@host $ \r\n```\r\n\r\nBytes:\r\n```python\r\ne = Exception()\r\ne.__notes__ = b\"a note\"\r\nraise e\r\n```\r\n```\r\nuser@host $ ./repro.py\r\nTraceback (most recent call last):\r\n  File \"./repro.py\", line 8, in \u003cmodule\u003e\r\n    raise e\r\nException\r\n97\r\n32\r\n110\r\n111\r\n116\r\n101\r\nuser@host $ \r\n```\r\n\r\nEven though the above are all edge cases, since there are some checks that handle these cases already, it makes sense to handle them more gracefully.\r\n\r\n# Your environment\r\n\r\n- CPython versions tested on: 3.12.0a7+\r\n- Operating system and architecture: macOS Mojave (x86)\r\n\r\n\u003c!-- gh-linked-prs --\u003e\r\n### Linked PRs\r\n* gh-103897\r\n\u003c!-- /gh-linked-prs --\u003e\r\n","author":{"url":"https://github.com/pR0Ps","@type":"Person","name":"pR0Ps"},"datePublished":"2023-04-26T21:37:55.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":5},"url":"https://github.com/103895/cpython/issues/103895"}