Unexpected line break in subscript

[cducrest]

Operating system: Linux
Python version: 3.6.7
Black version: 19.3b0
Does also happen on master: kind of

With black 19.3b0, I notice the following behaviour

# in == out:

def test_black_expected_behaviour():

    alice = pretty_long_name_but_not_too_long.action.do_something(
        action=None
    ).do_other_thing()[0]["args"]


def test_black_unexpected_behaviour():

    alice = pretty_long_name_and_actually_long_enough_to_make_it_weird.action.do_something(
        action=None
    ).do_other_thing()[
        0
    ][
        "args"
    ]

I would expect the second function to be formatted in a similar way as the first one. i tried it out with master version online

This brings the following result:

# out:

def test_black_expected_behaviour():

    alice = pretty_long_name_but_not_too_long.action.do_something(
        action=None
    ).do_other_thing()[
        0
    ][
        "args"
    ]


def test_black_unexpected_behaviour():

    alice = pretty_long_name_and_actually_long_enough_to_make_it_weird.action.do_something(
        action=None
    ).do_other_thing()[
        0
    ][
        "args"
    ]

This second result seems better because more consistent, but I am not sure it is the expected behaviour since for vertical whitespace, Black tries to render one full expression or simple statement per line. If this fits the allotted line length.

Feel free to close this issue if you consider this to be the wished for behaviour of black, or consider this as a bug / to be improved otherwise.

[graingert]

there seems to be a few duplicates of this:

#814
#1101
#1406

[ichard26]

Thank you @graingert for letting me know about those pesky duplicates! I typically don't check design issues for duplicates as clear duplicates are harder to identify. I've closed them now and marked them as duplicates.

[JelleZijlstra]

This is #236.