black: Inconsistent wrapping for long call chain

Method chaining is inconsistent when the overall expression is a call (rather than, say, an assignment). Not sure if this is a style change or a bug.

Describe the style change

It would be great if black were consistent in its wrapping such that it either chained horizontally or vertically, but not both within the same expression (at least within the same level in the call-nesting of an expression).

Examples in the current Black style

def func():
    thing("argument-1").thing("argument-2").thing("argument-3").thing(
        "argument-4",
    ).thing("argument-5").thing("argument-6").thing("argument-7").thing(
        "argument-8",
    ).thing(
        "argument-9",
    ).thing(
        "argument-10"
    ).thing(
        "argument-11"
    ).thing(
        "argument-12"
    )

Adding trailing commas doesn’t help, though I understand that that’s a separate issue (https://github.com/psf/black/issues/1671):

def func():
    thing("argument-1",).thing("argument-2",).thing("argument-3",).thing(
        "argument-4",
    ).thing("argument-5",).thing("argument-6",).thing("argument-7",).thing(
        "argument-8",
    ).thing(
        "argument-9",
    ).thing(
        "argument-10"
    ).thing(
        "argument-11"
    ).thing(
        "argument-12"
    )

Desired style

def func():
    thing(
        "argument-1",
    ).thing(
        "argument-2",
    ).thing(
        "argument-3",
    ).thing(
        "argument-4",
    ).thing(
        "argument-5",
    ).thing(
        "argument-6",
    ).thing(
        "argument-7",
    ).thing(
        "argument-8",
    ).thing(
        "argument-9",
    ).thing(
        "argument-10"
    ).thing(
        "argument-11"
    ).thing(
        "argument-12"
    )

Additional context

Possibly related issues:

About this issue

Original URL
State: closed
Created 3 years ago
Reactions: 7
Comments: 15

Most upvoted comments

Actually, in line with the documentation, I’d expect it to be formatted like this:

def func():
    (
        thing("argument-1")
        .thing("argument-2")
        .thing("argument-3")
        .thing("argument-4")
        .thing("argument-5")
        .thing("argument-6")
        .thing("argument-7")
        .thing("argument-8")
        .thing("argument-9")
        .thing("argument-10")
        .thing("argument-11")
        .thing("argument-12")
    )

which Black does keep (playground), but doesn’t quite produce.

felix-hilden on Jun 17, 2021

Oh, indeed! It should be #571 👍

felix-hilden on Jan 31, 2022

I agree that https://github.com/psf/black/issues/2279#issuecomment-863304112 is better than the current output, however due to the presence of trailing commas here I would expect that this would be wrapped as in my original report. I’m not sure what black should do given a similar input which didn’t have trailing commas.

PeterJCLaw on Jun 18, 2021

Another option would be to create some black ignored sections?

We have that, it’s called # fmt: off.

JelleZijlstra on Jun 17, 2021