Nested expression formatting

[MichaReiser]

I was surprised that there's no existing issue for this.

We decided not to implement the following Black 24 style changes:

• parenthesize_long_type_hints,
• wrap_long_dict_values_in_parens
• parenthesize_conditional_expressions

Because a) implementing this in Ruff is kind of hard (or slow) and b) it goes against the overall goal to avoid unnecessary parentheses.

This Black issue goes into more detail about our concerns. We should explore different designs that yields better sub-expression formatting without requiring optional parentheses to improve readability.

[vasily-v-ryabov]

Thanks for improving the Formatter! ruff check is awesome, though ruff format still could be a little bit more mature, but we are very positive about its future too!

Let me add some input examples here which may be useful test cases in the future. This one came from old PyLint 2.x rule W9500.

some_dict = {
    'This is the first line which well fits into one line of code',
    'This is the second very long and very annoying line for the '
        'demonstration of Ruff Formatter issue with hanging indent '
        'wrapped twice in total',
    'This is the third line which well fits into one line of code',
}

For the next example (lower priority to us, not a deal breaker) ruff format removes empty line before return statement only at the beginning of method / function while it keeps empty line before any other return statement.
This one came from old PyLint 2.x rule W9302, unnecessary-transfer-func-returns, Function returns should be transferred up. XX characters remain (it is triggered by PyLint 2.x when empty line is removed).

class Klass:
    def method1(
        self,
        other: str,
        another: str,
        one_more_argument: str,
    ) -> Optional[str]:

        return f'{other} is not {another} while {one_more_argument} happens'