Formatter removes line break between implicitly concatenated strings

[cnpryer]

Couldn't find an exact issue, but I'm almost certain this has been reported already.

Maybe related to #6936
Also see #5893

Line-length: 88

Black (23.7.0):

print(
    "aaaaaaa {:.2f}% "
    "aaaaaaaaaaaaaaaa".format(
        (
            ((df_aaaaaaaaaaa["fak"].isna()) | (df_aaaaaaaaaaa["fak"] == 0)).sum()
            / len(df_aaaaaaaaaaa)
        )
        * 100
    )
)

Ruff (0.0.287):

print(
    "aaaaaaa {:.2f}% " "aaaaaaaaaaaaaaaa".format(
        (
            ((df_aaaaaaaaaaa["fak"].isna()) | (df_aaaaaaaaaaa["fak"] == 0)).sum()
            / len(df_aaaaaaaaaaa)
        )
        * 100
    )
)

Playground: https://play.ruff.rs/126e4315-3c75-4268-b43a-12586c5da779

[MichaReiser]

Black applies special formatting for strings inside binary expressions. We have a "cheap" implementation that works for the most simple cases but it falls short in more complicated settings. I hope to have a fix for this by next week.

[charliermarsh]

We're marking this as an intentional deviation, since the resulting code doesn't exceed line width and reduces vertical spacing. (If you make the strings longer, we do split and format identically to Black.)

Can be closed once documented.