Unintentional formatter deviation: strange spacing around TypeAlias declarations

[stinodego]

Reproducible example:

from typing import TypeAlias

MultiColSelector: TypeAlias = (
    "slice | range | list[int] | list[str] | list[bool] | Series"
)

black leaves this alone, while ruff formats it as follows:

- MultiColSelector: TypeAlias = (
-     "slice | range | list[int] | list[str] | list[bool] | Series"
- )
+ MultiColSelector: (
+     TypeAlias
+ ) = "slice | range | list[int] | list[str] | list[bool] | Series"

This looks like an undesirable change to me.

In our code base, I worked around this by rewriting the string as a Union of types.

Command: ruff format .
Formatter settings: None
Version: ruff 0.1.2

P.S.: Other than the two minor issues I just reported, the new ruff formatter is working excellently. It has improved formatting in quite a few cases. Thank you for the amazing work!

[MichaReiser]

Thank's for reporting and thank you for the kind words.

This deviation is documented as type annotations may be parenthesized and is related to 7315.

Let's keep this issue open to collect some more feedback as I can see that the formatting in this case is not ideal. I also want to re-test if implementing #6975 (preview style) will make fixing it obsolete.

[henryiii]

AFAICT, the rule should be that type annotations are only parenthesized if the type annotation itself is long. It should never parenthesize a type annotation to make something after the equals sign have more space.

[charliermarsh]

We ended up reverting this decision (so we no longer have this Black deviation). Once we implement preview style, we should have roughly the behavior you describe.