Formatting of long expressions in arguments

[oskarkk]

Describe the style change

#3440 (closing #620 and #808) improved handling of long expressions in dict values by putting them in parentheses, but the same values in function arguments aren't always handled nicely.

Examples in the current Black style

dict(
    key_key_key_key=a_long_long_long_long_long
    * b_long_long_long_long_long
    / 100.0
)

dict(
    key_key_key_key_key_key_key_key_key=lambda: some_very_long_function_name(
        x, y, z
    )
)

Desired style

dict(
    key_key_key_key=(
        a_long_long_long_long_long * b_long_long_long_long_long / 100.0
    )
)

dict(
    key_key_key_key_key_key_key_key_key=(
        lambda: some_very_long_function_name(x, y, z)
    )
)

Additional context

The above problem surprisingly isn't present when the expression is the ternary operator. I found this related issue: #2248, and I think it could be closed now, as on the --preview on main it's fixed.

Here's a comparison of some structures where formatting is good and not good:

https://black.vercel.app/?version=main&state=_Td6WFoAAATm1rRGAgAhARYAAAB0L-Wj4AVtAZFdAD2IimZxl1N_Wg0-DjgFSwwpr4QAHGnZVCigXiEsaw3kDKWOCEa4OyVpau2mCKO2huSgEtYJFakCvJdOz0Tnz9A9VXZaY6yvVt0g0T7eVV1sdafqJHPQjFCF87XgeS5o61J0hfwUrJyv9vemJ3drIV67OMA4NPtoBxDB0jAnP0w3_FCw4CwHZNzHatn3Mmo8JDZbQgL9tZuHGhbY93lVPrMOOj7V13lJpYG7iN4EAeOxV-wIMLcnBSj9dt2P1447cRZOFBAPbIbLCz6KCdzbNRgUw7Z2AoNrHepi73I-BQJ-tVCrypINXFeYTLtWI5ijTFPZ_c48_7tnfGJvb9lSt20aVWHGlcDJzbeHWZA5x90aMTtBD_YqD4xSuSyF2kcLxHFGTemWtI7jxvkqSbsB1L1TVuEqG1ERUBH7wYVedEYUorPtewAk13xN8SdhklZ3xTKO_WsKJ2NSK4bvFkLnxJuMSyIlc0tGdWdyFUdJub9EJwuKoneabBy__ez6gsL3D1DbXrAxE-ETk4_7yaQi0S4AAAAAAK98cuj9XVqQAAGtA-4KAADgH0AascRn-wIAAAAABFla

Without preview enabled, cases A-J excluding E are ugly, with preview enabled only C, D, I and J are ugly (and these are the examples presented above).