Bug: linebreak in comparison in parens with comments in conditional is not stable

[Zac-HD]

Hypothesis is planning to adopt Black (HypothesisWorks/hypothesis#1686), but I noticed a weird linebreak when a condition follows a comment. Originally this was in this example, but the simple repro is as follows:

# Expected form
(
    # comment
    1 == 2
)

# Result of running Black on expected form
(
    # comment
    1
    == 2
)

Operating system: Windows
Python version: 3.6.5
Black version: 18.9b0
Does also happen on master: yes, commit 0b40a7

(and thanks so much to everyone contributing to Black - it's made Python development noticeably more fun by taking formatting entirely out of my brain 😍)

[Zac-HD]

Even better: applying Black to this code

if (
    # pre
    (1 == 2)
    # post
): ...

removes the inner parens, which then inserts the linebreak above. This in turn makes Black abort in --safe mode!

This more complex form only occurs if the parens are part of a more complex statement (if, while, for, etc) and does not happen in the 'expected form' above - if inner parens are added, they are retained by Black.

[ichard26]

Just rechecked, Black is no longer unstable, but is now deleting comments D:

[JelleZijlstra]

The example from the first post is no longer unstable. In the second example, Black now removes the # pre comment, which is still a bug.

[cnpryer]

Just rechecked, Black is no longer unstable, but is now deleting comments D:

I noticed this today. With

black, 23.3.0 (compiled: yes)
Python (CPython) 3.11.3

This statement will lose its # First inner comment:

# Some assert
assert (
    # First inner comment
    (1 + 1)  # Test's trailing comment 
    # Below the expression
    # Last inner comment
), "Some string"  # Message's trailing comment
# Below the assert