3.11 backtrace visual indicators are too verbose

[belm0]

I understand that the new visual indicators can be disabled, but we shouldn't have to choose between guaranteed 50% longer backtraces and pertinent column information.

Often, the visual indicator spans the entire line for a large percentage of the backtrace. (I've seen cases in our app where it's true for 100% of the backtrace.)

Proposal: elide the indicators when they span the whole line

Elide traceback column indicators when the entire line of the frame is implicated. This reduces traceback length and draws more attention to the remaining (very relevant) indicators.

before:

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

after:

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

[belm0]

I've prototyped the change for traceback.py. Making the equivalent change to C traceback code and updating documentation is still required. I'd like to hear if this change has some support from Python devs before putting more time into the PR.

[Zac-HD]

I am very, very keen on this change! Thanks very much @belm0 for thinking of this and implementing a patch 😍

[belm0]

PR #93994 is ready for review