[925] Improve multiline dictionary and list indentation for sole function parameter

[henriholopainen]

Description

Making multiline lists and dictionaries less indented when passed as a function parameter and pairing parens with brackets/braces was discussed at in #925. This PR introduces a conservative first step, where a multiline list or dict as the sole parameter to a function call will have special treatment for better readability. The feature is behind hug_parens_with_braces_and_square_brackets preview toggle.

Checklist - did you ...

• Add an entry in CHANGES.md if necessary?
• Add / update tests if necessary?
• Add new / update outdated documentation?

[github-actions]

diff-shades results comparing this PR (c066e69) to main (ef1048d). The full diff is available in the logs under the "Generate HTML diff report" step.

╭────────────────────────────── Summary ──────────────────────────────╮
│ 19 projects & 1112 files changed / 62 563 changes [+27 944/-34 619] │
│                                                                     │
│ ... out of 2 501 176 lines, 11 760 files & 23 projects              │
╰─────────────────────────────────────────────────────────────────────╯

Differences found.

What is this? | Workflow run | diff-shades documentation

[JelleZijlstra]

@henriholopainen seems like there's a crash on some code in Hypothesis (from the diff-shades failure). Can you take a look?

[henriholopainen]

Located the issue in Hypothesis (and other places); opening and closing brackets/braces don't necessary belong to the same entity. For example:

foooooooooooooooooooo([{c: n + 1 for c in range(256)} for n in range(100)] + [{}], {size})

becomes currently:

foooooooooooooooooooo([
    {c: n + 1 for c in range(256)} for n in range(100)] + [{}], {size
})

which is clearly very wrong. I'll add some test cases and look for a sophisticated approach for a fix tomorrow.

[henriholopainen]

Test cases added and logic fixed

[hauntsaninja]

Thanks for the PR! While I like the style, it's a fairly substantive change for black and goes against the philosophy of diff reduction (in the case you add or remove arguments). I wonder therefore if it makes sense to have magic trailing commas after the single arg prevent this reformatting.

[henriholopainen]

Thanks for the PR! While I like the style, it's a fairly substantive change for black and goes against the philosophy of diff reduction (in the case you add or remove arguments). I wonder therefore if it makes sense to have magic trailing commas after the single arg prevent this reformatting.

Do you mean that we should instead format

foo({0: "looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong line"},)

as it would be formatted without the trailing comma:

foo({
    0: "looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong line"
})

?

[Avasam]

How does (or should) this handle unpacking? I don't see a test to confirm intended behaviour there.

foo(*[
	pretend,
	many,
	and,
	long,
	arguments,
	# ... ..................................................................
	*another_list
])

[henriholopainen]

How does (or should) this handle unpacking? I don't see a test to confirm intended behaviour there.

Currently it doesn't, but adding support for that would make sense IMO.

[hauntsaninja]

It looks like Black already does what I suggested, I went ahead and added a test case and docs for it here: #3991

[JelleZijlstra]

Maybe I was too hasty in merging this. I think this makes things generally look better, but we should definitely think more about whether we want to go through before we move this change to stable.

[charliermarsh]

One question, as both a user and a Ruff maintainer: is it intended that this also applies to parenthesized lists, sets, etc., outside of function calls? For example, with this commit:

# Input
([1, 2, 3,])

# HEAD^
(
    [
        1,
        2,
        3,
    ]
)

# HEAD
([
    1,
    2,
    3,
])

[JelleZijlstra]

Not intentionally, but I don't mind that we remove the extra newlines there. Ideally we should also remove the parentheses.

[cthoyt]

This makes me so very happy, thanks @JelleZijlstra :)