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Issues when showing broken Exception.__notes__ #103895
Description
Bug report
When notes on an exception cannot be shown because the repr and str raise exceptions, a <note str() failed> message is shown instead. In the case where exception.__notes__ is not a sequence and cannot be shown, a <__notes__ repr() failed> is shown. In the second case, the message does not include a trailing newline.
__notes__ is a list containing a broken "note" - output includes a newline:
class A:
def __repr__(self):
raise Exception()
e = Exception()
e.__notes__ = [A()] # !!!
raise euser@host $ ./repro.py
Traceback (most recent call last):
File "./repro.py", line 8, in <module>
raise e
Exception
<note str() failed>
user@host $
__notes__ is just a single broken "note" - output does not include a newline:
class A:
def __repr__(self):
raise Exception()
e = Exception()
e.__notes__ = A() # !!!
raise euser@host $ ./repro.py
Traceback (most recent call last):
File "./repro.py", line 8, in <module>
raise e
Exception
<__notes__ repr() failed>user@host $
Additionally, when __notes__ is a string/bytes, the contents are expoded over multiple lines because of an isinstance(__notes__, Sequence) check.
String:
e = Exception()
e.__notes__ = "a note"
raise euser@host $ ./repro.py
Traceback (most recent call last):
File "./repro.py", line 8, in <module>
raise e
Exception
a
n
o
t
e
user@host $
Bytes:
e = Exception()
e.__notes__ = b"a note"
raise euser@host $ ./repro.py
Traceback (most recent call last):
File "./repro.py", line 8, in <module>
raise e
Exception
97
32
110
111
116
101
user@host $
Even 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.
Your environment
- CPython versions tested on: 3.12.0a7+
- Operating system and architecture: macOS Mojave (x86)
Activity
[-]No trailing newline when showing broken `Exception .__notes__`[/-][+]Issues when showing broken `Exception.__notes__`[/+]gaogaotiantian commentedon Apr 26, 2023
Is
Exception.__notes__supposed to be directly written?add_note()is definitely the recommended interface to use the feature. The docs mentioned__notes__as a "list of the notes", and is breaking that a "corner case", or simply the wrong way to use it?pR0Ps commentedon Apr 26, 2023
It is not supposed to be directly written (as far as I can tell), but while I was experimenting with some unrelated exception handling I was digging into this and noticed the inconsistency with the newlines so I figured I'd make a quick patch.
The only reason I bothered at all is because there's already some amount of handling of invalid notes so it seems it's at least been considered that someone may write
Exception.__notes__directly.gh-103895: Improve how invalid `Exception.__notes__` are displayed (#…
iritkatriel commentedon May 1, 2023
Merged into 3.12. Leaving open pending decision about backporting to 3.11.
Merge branch 'main' into supermon
Merge branch 'main' into inlinecomp2
iritkatriel commentedon Jun 27, 2023
Assigned to @ambv for a backport decision.
hugovk commentedon Nov 10, 2023
@ambv Shall we backport or close this issue?