Feature request: Add support for python Black

[iemejia]

Python's Black has become the de-facto code auto-formatter for python. It would be great if we could call it with spotless.

[nedtwigg]

The key thing needed to integrate with Spotless is a Function<String, String>. So if you can either

A) Write some python code that configures the formatter, then has a function that consumes a string and returns a string
B) Find some commandline flags which accomplishes this (e.g. read on stdin and write to stdout, or possibly read some tempfile and write back out to it)

then that's the first step. The second step is integrating python and JVM, for which I believe there are many alternatives.

[rpdelaney]

Find some commandline flags which accomplishes this (e.g. read on stdin and write to stdout, or possibly read some tempfile and write back out to it)

black --code "$text"

demo

$ cat source.py
from seven_dwwarfs import Grumpy, Happy, Sleepy, Bashful, Sneezy, Dopey, Doc
x = {  'a':37,'b':42,

'c':927}

x = 123456789.123456789E123456789

if very_long_variable_name is not None and \
 very_long_variable_name.field > 0 or \
 very_long_variable_name.is_debug:
 z = 'hello '+'world'
else:
 world = 'world'
 a = 'hello {}'.format(world)
 f = rf'hello {world}'
if (this
and that): y = 'hello ''world'#FIXME: https://github.com/python/black/issues/26
class Foo  (     object  ):
  def f    (self   ):
    return       37*-2
  def g(self, x,y=42):
      return y
def f  (   a: List[ int ]) :
  return      37-a[42-u :  y**3]
def very_important_function(template: str,*variables,file: os.PathLike,debug:bool=False,):
    """Applies `variables` to the `template` and writes to `file`."""
    with open(file, "w") as f:
     ...
# fmt: off
custom_formatting = [
    0,  1,  2,
    3,  4,  5,
    6,  7,  8,
]
# fmt: on
regular_formatting = [
    0,  1,  2,
    3,  4,  5,
    6,  7,  8,
]
$ black --code "$(<source.py)"
from seven_dwwarfs import Grumpy, Happy, Sleepy, Bashful, Sneezy, Dopey, Doc

x = {"a": 37, "b": 42, "c": 927}

x = 123456789.123456789e123456789

if (
    very_long_variable_name is not None
    and very_long_variable_name.field > 0
    or very_long_variable_name.is_debug
):
    z = "hello " + "world"
else:
    world = "world"
    a = "hello {}".format(world)
    f = rf"hello {world}"
if this and that:
    y = "hello " "world"  # FIXME: https://github.com/python/black/issues/26


class Foo(object):
    def f(self):
        return 37 * -2

    def g(self, x, y=42):
        return y


def f(a: List[int]):
    return 37 - a[42 - u : y ** 3]


def very_important_function(
    template: str, *variables, file: os.PathLike, debug: bool = False,
):
    """Applies `variables` to the `template` and writes to `file`."""
    with open(file, "w") as f:
        ...


# fmt: off
custom_formatting = [
    0,  1,  2,
    3,  4,  5,
    6,  7,  8,
]
# fmt: on
regular_formatting = [
    0,
    1,
    2,
    3,
    4,
    5,
    6,
    7,
    8,
]

$

[nedtwigg]

Implemented in #672, shipped in plugin-gradle 5.2.0 (tweet), PR for maven is welcome. The setup experience could be better, we'll track that at #674.

[iemejia]

Great ! 👏 thanks!

[nedtwigg]

@iemejia, @rpdelaney, do you have any feedback on what info would be helpful for the black docs: psf/black#1622