issue #41: backport the pure python suggestion code from 3.12

[cfbolz]

First attempt. Code is from here: python/cpython@bbc7cd6

I suppose a few more tests would be good?

[agronholm]

I suppose a few more tests would be good?

Passing tests would be good :)

[cfbolz]

That too ;-)

[cfbolz]

of course it passes locally on 3.10 and pypy, otherwise I wouldn't have pushed. how do you usually run tests locally?

[agronholm]

of course it passes locally on 3.10 and pypy, otherwise I wouldn't have pushed. how do you usually run tests locally?

I usually just run tox -p before pushing.

[cfbolz]

so 3.11 fails, because there exceptiongroup.format_exception etc just defer to the traceback module, which does not do suggestions in 3.11 yet. I could 1) skip the test there or 2) change the logic in __init__.py to use 3.12 as the cutoff, because traceback.py will have suggestion support there.

[agronholm]

I'm a bit confused; the test suite should not be calling exceptiongroup.format_exception() at all on Python 3.11. Instead it should be calling traceback.format_exception(). Since nothing is being patched on 3.11, it should "just work", yes?

[agronholm]

Ok so, let me change the question. With exceptiongroup not patching anything on 3.11, it also won't break anything, right? If that is so, then skipping the test on 3.11 seems like the right thing to do.

[coveralls]

Pull Request Test Coverage Report for Build 3464828665

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 602 unchanged lines in 6 files lost coverage.
• Overall coverage decreased (-9.08%) to 64.971%

---

Files with Coverage Reduction	New Missed Lines	%
/opt/hostedtoolcache/Python/3.10.8/x64/lib/python3.10/site-packages/exceptiongroup/_formatting.py	22	91.72%
/opt/hostedtoolcache/Python/3.9.15/x64/lib/python3.9/site-packages/exceptiongroup/_formatting.py	91	67.55%
/opt/hostedtoolcache/Python/3.7.15/x64/lib/python3.7/site-packages/exceptiongroup/_formatting.py	92	67.33%
/opt/hostedtoolcache/Python/3.8.14/x64/lib/python3.8/site-packages/exceptiongroup/_formatting.py	92	67.55%
/opt/hostedtoolcache/PyPy/3.8.13/x64/lib/pypy3.8/site-packages/exceptiongroup/_formatting.py	145	17.22%
/opt/hostedtoolcache/Python/3.11.0/x64/lib/python3.11/site-packages/exceptiongroup/_formatting.py	160	0%

Totals
Change from base Build 3457158244:	-9.08%
Covered Lines:	2018
Relevant Lines:	3106

---

💛 - Coveralls

[cfbolz]

With exceptiongroup not patching anything on 3.11, it also won't break anything, right? If that is so, then skipping the test on 3.11 seems like the right thing to do.

Yes, that reasoning makes a lot of sense, I just did that.

[agronholm]

Goodie! Anything missing from the PR? I see it's still marked as draft.

[cfbolz]

no, good from my side

[agronholm]

Thanks!

[cfbolz]

awesome, thank you!

[jdavies-st]

So currently in Python 3.11.0, the suggestions for NameError and AttributeError still seem to be computed on-the-fly and are not a part of the traceback. An example:

>>> class Foo:
...     def _bar(self):
...         return 42
... 
>>> foo = Foo()
>>> foo.bar
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'Foo' object has no attribute 'bar'. Did you mean: '_bar'?
>>> try:
...     foo.bar
... except AttributeError as e:
...     print(e)
... 
'Foo' object has no attribute 'bar'

Is this supposed to change during some patch release of 3.11.x?

[agronholm]

From what I understood, this would be changing in Python 3.12. It's a non-issue on 3.11 as this project doesn't do monkey patching on that version (or any subsequent versions).

[jdavies-st]

Thanks. Then perhaps the issue we are seeing in astropy/astropy#14005 is actually an upstream usage of exceptiongroup by pytest. In terms of NameError and AttributeError suggestions, Python 3.10 and 3.11 should be treated the same, but now 3.10 is being patched (to work like 3.12), but 3.11 is not.