An error occurred while Style/TrailingCommaInArguments cop was inspecting

[pboling]

TL;DR

• Reproduction: https://github.com/rubocop-lts/Style-TrailingCommaInArguments
• Bug is present in latest 2.x release
• Bug is present in the 2-stable branch.
• Bug is not present in latest main branch, targeting v3 release
• If no further releases of 2.x are planned this can probably be ignored
• Reporting because I didn't find any mention of the bug in the tracker
• Perhaps it was fixed in a beneficial refactor.

P.S. I loved meeting so many Shopify people at #RubyKaigi a couple weeks ago! I promised several of them that I would (re)apply, and haven't done it yet. But I will.

Details

When running RuboCop on a project I saw the following errors:

2 errors occurred:
An error occurred while Style/TrailingCommaInArguments cop was inspecting /IdeaProjects/kettle-soup-cover/kettle-soup-cover.gemspec:52:15.
An error occurred while Style/TrailingCommaInArguments cop was inspecting /IdeaProjects/kettle-soup-cover/kettle-soup-cover.gemspec:59:26.

Errors are usually caused by RuboCop bugs.
Please, update to the latest RuboCop version if not already in use, and report a bug if the issue still occurs on this version.
https://github.com/rubocop/rubocop/issues

Mention the following information in the issue report:
1.75.4 (using Parser 3.3.8.0, rubocop-ast 1.44.1, analyzing as Ruby 2.7, running on ruby 3.4.2) [x86_64-linux]

The code at those specific lines was:

  spec.files = Dir[
    "lib/**/*.rb",
    "lib/**/rakelib/*.rake",
    "sig/**/*.rbs",
  ]

and

  spec.extra_rdoc_files = Dir[
    "CHANGELOG.md",
    "CODE_OF_CONDUCT.md",
    "CONTRIBUTING.md",
    "LICENSE.txt",
    "README.md",
    "SECURITY.md",
  ]

In both cases the error pointed to the D in Dir on the first line of each.

In narrowing down the culprit of the bug I found that it was triggered by rubocop-shopify, not rubocop.

NOTE: The bug does not occur if Dir.glob([...]) is used instead of Dir[...].

I was able to create a reproduction of the bug in this repository using the
latest 2.x release of the rubocop-shopify gem.
The bug does not occur with vanilla rubocop.
The bug has been fixed in Shopify's main branch which is targeting the not-yet-released v3.0!
Unless a new release of the 2.x line is planned this probably doesn't need further review.

[sambostock]

Thanks for the report but this was a bug upstream (rubocop/rubocop#14137), which was fixed in rubocop/rubocop#14138. 😅

It was reproducible when depending on rubocop-shopify because we override this cop's default config, revealing the bug

ruby-style-guide/rubocop.yml

Lines 978 to 979 in b094a0f

	Style/TrailingCommaInArguments:
	EnforcedStyleForMultiline: comma

while on main we've disabled this cop (and most others – see #687).