Style/Filename gives wrong diagnostic for some known ruby file names

[MarkVillacampa]

Rubocop will interpret a file named Dangerfile as having ruby source, but will throw an invalid name error.

Diving in Rubocop's source, I've identified the list of file names to be considered Ruby source:

https://github.com/bbatsov/rubocop/blob/66405e118491afd8e8ec574cf2dc18549ef9a2df/lib/rubocop/target_finder.rb#L32-L52

In default.yml there is an interesting comment in the Style/Filename cop:

Style/FileName:
  # File names listed in `AllCops:Include` are excluded by default. Add extra
  # excludes here.

https://github.com/bbatsov/rubocop/blob/ef729dfcc5d15e038db24579b761bc0b56991de0/config/default.yml#L503-L505

If we go to AllCops:Include in the same file, we find an interesting list of files:

https://github.com/bbatsov/rubocop/blob/ef729dfcc5d15e038db24579b761bc0b56991de0/config/default.yml#L9-L29

These two lists have a big overlap but are not identical.

As I see it, to solve my particular issue I would need to add Dangerfile to AllCops:Include, but I'm wondering if these two lists of potential Ruby files shouldn't be merged instead of being maintained separately?

I want to hear what folks think. I'll be happy to send a PR when/if someone more knowledgeable in the codebase gives me some pointers :)

Expected behavior

The Style/Filename cop show show be triggered by known Ruby file names.

Actual behavior

$ rubocop Dangerfile
Inspecting 1 file
C

Offenses:

Dangerfile:1:1: C: The name of this source file (Dangerfile) should use snake_case.
# Make it more obvious that a PR is a work in progress and shouldn't be merged yet
^

1 file inspected, 1 offense detected

Steps to reproduce the problem

1- Create a file named Dangerfile
2- Run rubocop Dangerfile

RuboCop version

$ rubocop -V
0.48.1 (using Parser 2.4.0.0, running on ruby 2.4.0 x86_64-darwin16)

[bbatsov]

Seems like an oversight on our part. Guess we should merge those lists and ideally rely on the configuration so users can change the list themselves.

[bbatsov]

I've synced up the two lists for now, but down the road this duplication should really be taken care of.

[ryanhageman]

Is this still an issue?

[koic]

@ryanhageman Thank you for mentioning. This issue has been solved by edge RuboCop with #5882.