Extra indentation at function definition

[jsh9]

Hi @jni, @flexatone, @Martmists-GH, @stefanoborini, @mintchkin, @nbievre:

I recently forked Black and wrote a more configurable Python code formatter (named "Cercis": https://github.com/jsh9/cercis), because I do not agree with this particular style choice of Black, and Black does not offer customization for it:

def some_function(
    arg1: int,
    arg2: bool,
    arg3: float,
    arg4_with_long_name: str,
) -> bool:
    ...

After some Googling, I think you share the same style opinion as I do. Here are the posts that I looked at:

• Continuation lines defined by extra indentation grantjenks/blue#89
• Comply with PEP-8 for indentation of parameters in function definition grantjenks/blue#90
• Black does not create pylint-compatible code psf/black#1127
• Adjusting to PEP8 Style for function with long list of parameters psf/black#2117
• Black violates pep8 recommendation with long argument list psf/black#1178

---

Cercis does this out of the box:

def some_function(
        arg1: int,
        arg2: bool,
        arg3: float,
        arg4_with_long_name: str,
) -> bool:
    ...

It is controlled by an option --function-definition-extra-indent, which is by default True.

With the --closing-bracket-indentation option set to True (by default, this option is False), we can get this:

def some_function(
        arg1: int,
        arg2: bool,
        arg3: float,
        arg4_with_long_name: str,
        ) -> bool:
    ...

If you are still interested in implementing this style in your code, please feel free to try it out, and any feedback would be appreciated!

[jni]

Brilliant! Thanks for the ping! I'll give it a try. Many of the projects I work with are much bigger so I can't control a change away from black, but I'll give this a go with new projects! 🙏

[jni]

@jsh9 does this also do extra indentation for line continuation in general? ie I like to use 8 spaces not just for function def but function calls, multi-line conditionals, etc.

[jsh9]

If I'm to implement 8 spaces, I might as well also support options of 2 spaces and tabs.

For the option of 2 spaces, what does everything think of the following style?

(There are 2 spaces in the argument list, rather than 4, or 8)

def function(
  arg1_with_very_long_name: int,
  arg2_with_very_long_name: float,
  arg3_with_very_long_name: list,
):
  print('Yes')

(There are 2 spaces in the argument list, rather than 4, or 8.)

I'm personally OK with this style, because the 3 input arguments have a visually clean separation from def function.

[jni]

No no, my point is not to make all indentation 8 spaces, but to make all line continuation 8 spaces, to distinguish it from logical blocks. This is what PEP8 recommends.

[jsh9]

I see. I couldn't find the recommendation of using 8 spaces in line continuation in PEP8 (https://peps.python.org/pep-0008/). Could you point me to it?

This style you are suggesting (8 spaces for line continuation and 4 spaces for blocks) is indeed the default style for Java in IntelliJ, so I can definitely see the appeal of it. Let me look into how to implement it.

[jsh9]

Hi @jni, please check out version 0.1.5. I implemented configurable indentation for line continuation.

There are now 3 options for granular tweaking the code style:

• --function-definition-extra-indent
• --other-line-continuation-extra-indent
• --closing-bracket-extra-indent

The 2nd one is what you requested.

I also added a --base-indentation-spaces option.

Here is a quick example:

# --base-indentation-spaces = 2
# --function-definition-extra-indent = False
# --other-line-continuation-extra-indent = True
# --closing-bracket-extra-indent = True
def some_func(
  arg1,
  arg2,
  ):
  print(1)

result = [
    1,
    2,
    ]

Another example:

# --base-indentation-spaces = 3
# --function-definition-extra-indent = True
# --other-line-continuation-extra-indent = False
# --closing-bracket-extra-indent = True
def some_func(
      arg1,  # indent 6 spaces here
      arg2,
      ):
   print(1)

result = [
   1,  # indent 3 spaces here
   2,
   ]

[jni]

Thanks! Indeed I see looking more closely at the PEP8 examples that I had overgeneralised from this statement:

When using a hanging indent the following should be considered; there should be no arguments on the first line and further indentation should be used to clearly distinguish itself as a continuation line:

But this is what I'm talking about:

# Add some extra indentation on the conditional continuation line.
if (this_is_one_thing
        and that_is_another_thing):
    do_something()

Basically the argument here:

# Add 4 spaces (an extra level of indentation) to distinguish arguments from the rest.
def long_function_name(
        var_one, var_two, var_three,
        var_four):
    print(var_one)

Applies to any block that is indented, including with, while, for, if;

I find the 8 spaces indents for continuation (any continuation) useful to help me visually group lines — 4 spaces -> code block; 8 spaces -> mentally note this is a long line. I can glance at a function and count the number of statements, which is harder to do if line continuations are four spaces like the function def.

Thanks for the work!!! ❤️

[stefanoborini]

about damn time that someone resists that formatting cult that is black. Well done.

[jsh9]

Hi @veritas9872, @nilsbunger:

I saw your posts (astral-sh/ruff#1904 (comment)) and/or upvote to request extra indentation in the function argument list.

In particular, @veritas9872 mentioned here that:

Black continues to use its current indentation for arguments as changing it would be too disruptive

In fact, it is not difficult to implement, and it is not disruptive. I forked Black a few weeks ago and added this configurable option.

Please feel free to check out https://github.com/jsh9/cercis, and the option I added is : --function-definition-extra-indent.

My fork is on top of the latest changes of Black and I plan to keep rebasing on top of it.

Please feel free to take a look and provide feedback if any!

[jsh9]

Hi @jni, @flexatone, @Martmists-GH, @stefanoborini, @mintchkin, @nbievre, @veritas9872, @nilsbunger:

Ruff is implementing a Python code formatter, and I think the authors of Ruff are open-minded about adding configuration options. If you'd like this 8-space indentation feature implemented in Ruff, would you mind going to upvote my comment here:: astral-sh/ruff#1904 (comment)

Thanks!

[jsh9]

I think using Ruff is a better long-term solution than forking Black and making changes.

[jni]

I agree but by my reading the Ruff developers' willingness to implement options is quite limited. Anyway, I've upvoted. 🙏 Thank you again for your work! 🙏

[jsh9]

This time it may not be that easy for me to fork and tweak, because I don't code in Rust at all. :-(

[jni]

Sure, but it's not like black is going to disappear. I'd rather use cercis than black-from-ruff. 😜 So I hope you still have your original plan...

[jsh9]

Hi @LeonarddeR, welcome to the club! Please take a look at this discussion thread and the repo.