As it says in its documentation, walk_stack was meant to just
follow `f.f_back` like other functions in the traceback module.
Instead it was previously doing `f.f_back.f_back` and then this
changed to `f_back.f_back.f_back.f_back' in Python 3.11 breaking
its behavior for external users.
This happened because the walk_stack function never really had
any good direct tests and its only consumer in the traceback module was
`extract_stack` which passed the result into `StackSummary.extract`.
As a generator, it was previously capturing the state of the stack
when it was first iterated over, rather than the stack when `walk_stack`
was called. Meaning when called inside the two method deep
`extract` and `extract_stack` calls, two `f_back`s were needed.
When 3.11 modified the sequence of calls in `extract`, two more
`f_back`s were needed to make the tests happy.
This changes the generator to capture the stack when `walk_stack` is
called, rather than when it is first iterated over. Since this is
technically a breaking change in behavior, there is a versionchanged
to the documentation. In practice, this is unlikely to break anyone,
you would have been needing to store the result of `walk_stack` and
expecting it to change.
Previously, `traceback.print_list` didn't have a documentation entry and was not exposed in `traceback.__all__`. Now it has a documentation entry and is exposed in `__all__`.
Relevant tests moved from test_exceptions to test_traceback to be able to
compare both implementations.
Co-authored-by: Carl Friedrich Bolz-Tereick <cfbolz@gmx.de>
* gh-93883: elide traceback indicators when possible
Elide traceback column indicators when the entire line of the
frame is implicated. This reduces traceback length and draws
even more attention to the remaining (very relevant) indicators.
Example:
```
Traceback (most recent call last):
File "query.py", line 99, in <module>
bar()
File "query.py", line 66, in bar
foo()
File "query.py", line 37, in foo
magic_arithmetic('foo')
File "query.py", line 18, in magic_arithmetic
return add_counts(x) / 25
^^^^^^^^^^^^^
File "query.py", line 24, in add_counts
return 25 + query_user(user1) + query_user(user2)
^^^^^^^^^^^^^^^^^
File "query.py", line 32, in query_user
return 1 + query_count(db, response['a']['b']['c']['user'], retry=True)
~~~~~~~~~~~~~~~~~~^^^^^
TypeError: 'NoneType' object is not subscriptable
```
Rather than going out of our way to provide indicator coverage
in every traceback test suite, the indicator test suite should
be responible for sufficient coverage (e.g. by adding a basic
exception group test to ensure that margin strings are covered).
Pablo Galindo Salgado