Cannot enable rubocop-rspec derived cops on DisabledByDefault

[r7kamura]

To enable only certain cops derived from rubocop-rspec, I configured DisabledByDefault: true and tried to enable RSpec/EmptyExampleGroup like this:

# .rubocop.yml
require:
  - rubocop-rspec

AllCops:
  DisabledByDefault: true

RSpec/EmptyExampleGroup:
  Enabled: true

ref: #7923

Expected behavior

I expected RSpec/EmptyExampleGroup to be enabled like this:

$ bundle install
$ bundle exec rubocop
Inspecting 3 files
.C.

Offenses:

spec/example_spec.rb:2:3: C: RSpec/EmptyExampleGroup: Empty example group detected.
  context 'with empty example group' do
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

3 files inspected, 1 offense detected

Actual behavior

But RSpec/EmptyExampleGroup is not enabled:

$ bundle install
$ bundle exec rubocop
Inspecting 3 files
...

3 files inspected, no offenses detected

Steps to reproduce the problem

# Gemfile
source 'https://rubygems.org'

gem 'rspec'
gem 'rubocop'
gem 'rubocop-rspec'

# .rubocop.yml
require:
  - rubocop-rspec

AllCops:
  DisabledByDefault: true

RSpec/EmptyExampleGroup:
  Enabled: true

# spec/example_spec.rb
RSpec.describe 'Example' do
  context 'with empty example group' do
  end
end

RuboCop version

$ bundle exec rubocop -V
1.6.1 (using Parser 2.7.2.0, rubocop-ast 1.3.0, running on ruby 2.7.2 x86_64-linux)
  - rubocop-rspec 2.0.1

[r7kamura]

This problem doesn't happen on rubocop-rails. I think this is because rubocop-rspec has RSpec department in its config/default.yml, while rubocop-rails does not..

• https://github.com/rubocop-hq/rubocop-rspec/blob/56d801cffb74a9e89876336932e196eb128d9209/config/default.yml#L2
• https://github.com/rubocop-hq/rubocop-rails/blob/39bd3939a128c027d26dbfd95a98af19074a818f/config/default.yml

Because of this difference, RSpec department['Enabled'] returns false, while Rails department['Enabled'] returns nil .

https://github.com/rubocop-hq/rubocop/blob/f703e77ef32312c68e6fdcffcd95eb80e38200a2/lib/rubocop/config.rb#L283-L289

Maybe this false is set in this part:

https://github.com/rubocop-hq/rubocop/blob/f703e77ef32312c68e6fdcffcd95eb80e38200a2/lib/rubocop/config_loader_resolver.rb#L71-L75

override_department_setting_for_cops is called before this part, so it can't set "override_department" to RSpec/EmptyExampleGroup because RSpec dept is not yet disabled in this phase.

https://github.com/rubocop-hq/rubocop/blob/f703e77ef32312c68e6fdcffcd95eb80e38200a2/lib/rubocop/config_loader_resolver.rb#L109-L115

[dvandersluis]

This was really hairy but I have a PR incoming.