Line breaking behavior for function arguments with and without trailing comma

Hello and thanks for YAPF. It’s been working nicely for us, except for the formatting of long function arguments. Take a look at the example below. If a trailing comma is present, we would like to keep the them in individual lines. Without trailing comma, an option to break right after the opening parenthesis would be nice. This is PEP8 conform (as is the the YAPF output) and plays more nicely with with long function names.

Desired format:

a_very_long_function_name(
    long_argument_name_1=1,
    long_argument_name_2=2,
    long_argument_name_3=3,
    long_argument_name_4=4,
)

a_very_long_function_name(
    long_argument_name_1=1, long_argument_name_2=2,
    long_argument_name_3=3, long_argument_name_4=4)

YAPF output:

a_very_long_function_name(long_argument_name_1=1,
                          long_argument_name_2=2,
                          long_argument_name_3=3,
                          long_argument_name_4=4, )

a_very_long_function_name(long_argument_name_1=1,
                          long_argument_name_2=2,
                          long_argument_name_3=3,
                          long_argument_name_4=4)

[malcolmgreaves]

Hello! I have been evaluating bringing in yapf to a few projects. I found this thread and realized that the this issue applies to my current adoption. Has there been any resolutions, updates, or work-arounds discovered?

[Chaoste]

Maybe there was a misunderstanding what behavior we would like a trailing comma to cause. If there is a trailing comma, each argument and the closing parenthesis should have their own lines to easily edit individual arguments (regardless of line length and DEDENT_CLOSING_BRACKETS knob). Some examples to illustrate:

function_name(argument_name_1=1, argument_name_2=2, argument_name_3=3)

# Break even though this would fit into a single line.
function_name(
    argument_name_1=1,
    argument_name_2=2,
    argument_name_3=3,
)

a_very_long_function_name(
    long_argument_name_1=1, long_argument_name_2=2, long_argument_name_3=3,
    long_argument_name_4=4)

a_very_long_function_name(
    long_argument_name_1=1,
    long_argument_name_2=2,
    long_argument_name_3=3,
    long_argument_name_4=4,
)