Formatter: long walrus operator expression introduces parentheses

[tjkuson]

trafficstars

This seems similar to #7246 which was closed as completed, but reproducible in the latest 0.1.4 release.

Input:

if True:
    if True:
        if True:
            if True:
                if foo := some.very.very.very.very.very.very.very.very.very.long.function(
                    search.study_id
                ):
                    pass

Ruff formatter output:

if True:
    if True:
        if True:
            if True:
                if (
                    foo
                    := some.very.very.very.very.very.very.very.very.very.long.function(
                        search.study_id
                    )
                ):
                    pass

Black doesn't make any changes to the input file.

Ruff playground

[tjkuson]

Behaviour is the same for long method chains.

Input:

if True:
    if True:
        if True:
            if True:
                if foo == some.very.very.very.very.very.very.very.very.long_function_name(
                    bar
                ):
                    pass

Output:

if True:
    if True:
        if True:
            if True:
                if (
                    foo
                    == some.very.very.very.very.very.very.very.very.long_function_name(
                        bar
                    )
                ):
                    pass

EDIT: I marked this as outdated as the revised reproduction in the original post now details this behaviour.

[charliermarsh]

I see the same behavior in Black, or am I misunderstanding?

https://black.vercel.app/?version=main&state=_Td6WFoAAATm1rRGAgAhARYAAAB0L-Wj4AFGAIRdAD2IimZxl1N_Wlws4TBexXdmg613D2cRmmkK6QFkhhlNwTAUx4cz8BUeWx-cuwgYYrUzOEI2SVBXlwXRQgtbOqCvafh3iEcmeVpQMwvjow_MFJgqFPO0sgLW_4N7UAXeDoEHF1scyvxK89Ro-KbTojpHo8ZMycPjVc16iGNlSFE4PBe88ADJBimajoVexAABoAHHAgAAUu43D7HEZ_sCAAAAAARZWg==

[tjkuson]

Sorry, I made an error in the reproduction!

Input:

if True:
    if True:
        if True:
            if True:
                if foo := some.very.very.very.very.very.very.very.very.very.long.function(
                    search.study_id
                ):
                    pass

Ruff

if True:
    if True:
        if True:
            if True:
                if (
                    foo
                    := some.very.very.very.very.very.very.very.very.very.long.function(
                        search.study_id
                    )
                ):
                    pass

Black

if True:
    if True:
        if True:
            if True:
                if foo := some.very.very.very.very.very.very.very.very.very.long.function(
                    search.study_id
                ):
                    pass

[tjkuson]

(I've updated the original post to include the proper reproduction.)

[MichaReiser]

It seems that black formats the walrus operator more closely to assignments where it only breaks the right but never the left (or before/after the operator), even if doing so would help fitting the content on the line.