auto-gen-conf breaks default exclude in Rails/ApplicationRecord cop

[Aqualon]

Not sure if this is a bug in the Rails/ApplicationRecord cop or in rubocop itself

---

Expected behavior

Default exclude from the cop should always be considered

Actual behavior

I get complaints about

Rails/ApplicationRecord: Models should subclass ApplicationRecord.

in some spec files. After bundle exec rubocop --auto-gen-conf I got the same complaints about files in db/migrate/ directory, that should be excluded since #1349.

Generate config in .rubocop_todo.yml

# Offense count: 5
# This cop supports unsafe autocorrection (--autocorrect-all).
Rails/ApplicationRecord:
  Exclude:
    - 'spec/feature_helper.rb'
    - 'spec/models/concerns/paperclip_image_spec.rb'
    - 'spec/models/concerns/stat_counters_spec.rb'

Steps to reproduce the problem

• Create a db migration file with inheritance from ActiveRecord::Base (see Rails/ApplicationModel should ignore db/migrate/** #1342 for example)
• Run rubocop and get no complaints about the file
• Add config for Rails/ApplicationRecord excluding any file you want
• Rerun rubocop and get complaint about the migration file

RuboCop version

❯ bundle exec rubocop -V
1.67.0 (using Parser 3.3.5.0, rubocop-ast 1.32.3, analyzing as Ruby 3.3, running on ruby 3.3.5) [arm64-darwin23]
  - rubocop-capybara 2.21.0
  - rubocop-factory_bot 2.26.1
  - rubocop-performance 1.22.1
  - rubocop-rails 2.26.1
  - rubocop-rspec 3.1.0

[dvandersluis]

I don’t think this is specific to any cop. When multiple configuration files are loaded, by default keys present in both are overridden.

You can change this behavior by specifying inherit_mode: https://docs.rubocop.org/rubocop/configuration.html#merging-arrays-using-inherit_mode

# in .rubocop.yml

inherit_mode:
  merge:
    - Exclude

[Aqualon]

Thanks, seems this was supposed to be addressed in rubocop/rubocop#9624 to make it less confusing, but got nowhere.

[Earlopain]

It's pretty unfortunate, but the behaviour can only be changed in a major version bump of rubocop.

I do believe there is a bug here however. When generating a todo, it's supposed to warn you about this. https://github.com/rubocop/rubocop/blob/75160946ac3620005874d5188101dab77d585be2/lib/rubocop/formatter/disabled_config_formatter.rb#L229-L248

But because rubocop-rails own config already specifies a inherit_mode, it falls through. I don't know what the appropriate fix would be to show this warning, if even possible.