Parenthesize complex expressions passed as keyword arguments or parameter defaults - #4925

I'm split on this. I agree in most cases it improves formatting, but it does affect a lot of code. In some cases it feels unnecessary to me (like when the only operator is not or await). Would love to hear other maintainers' opinions!

Thanks for the feedback.

When I ran it locally on the Django codebase, there were around 500 changes, which may seem like a lot, but it's only 0.1% of all ~500k lines of code.

As for not, I've seen some people already parenthesize it, like in the previously linked example from django or another one from numpy. However, the main point of this PR was to add parentheses around binary operations, so we could definitely exclude not/await if this is what other maintainers agree with, just like there's already an exclusion for lambdas (where parentheses also felt unnecessary to me).

I've stumbled upon an issue that this PR would fix: #3510 (minus the lambda part, though both versions are fine IMO). Example from Django:

    rebate = models.GeneratedField(
-       expression=Coalesce("price", 0)
-       - Coalesce("discounted_price", Coalesce("price", 0)),
+       expression=(
+           Coalesce("price", 0) - Coalesce("discounted_price", Coalesce("price", 0))
+       ),
        output_field=models.IntegerField(),
        db_persist=False,
    )

The lambda part is covered by #3606, so I've linked the issue to this PR

diff-shades results comparing this PR (54b6e04) to main (1f8cbba):

--stable style: no changes

What is this? | Workflow run | diff-shades documentation

Hey, I wanted to ask about the status of this PR. Is there something I should do so that it can move forward?

In #3095 and #3494 (probably duplicates), there was a similar idea of adding parentheses in confusing expressions like *a + b, and both issues were accepted as worth implementing back then. Will this PR get any more interest if I generalize it to handle also those unpacking cases (as the logic should be identical), or should we just close it?