Rubocop + Standardrb + Rubocop Rspec

.rubocop-rails.yml

# .rubocop-rails.yml

.rubocop-rspec.yml

# .rubocop-rspec.yml

RSpec/ExampleLength:
  Enabled: false
RSpec/MultipleExpectations:
  Enabled: false

.rubocop.yml

# .rubocop.yml

inherit_mode:
  merge:
    - Exclude

require:
  - rubocop-rails
  - rubocop-rspec
  - rubocop-performance
  - standard/cop/block_single_line_braces  

inherit_gem:
  standard: config/base.yml

inherit_from:
  - .rubocop_rails.yml
  - .rubocop_rspec.yml
  
# Standardrb overrides
Style/TrailingCommaInArguments:
  Description: 'Checks for trailing comma in argument lists.'
  StyleGuide: 'https://github.com/bbatsov/ruby-style-guide#no-trailing-array-commas'
  EnforcedStyleForMultiline: comma
  SupportedStylesForMultiline:
    - comma
    - consistent_comma
    - no_comma
  Enabled: true

Style/TrailingCommaInHashLiteral:
  Description: 'Checks for trailing comma in hash literals.'
  StyleGuide: 'https://github.com/bbatsov/ruby-style-guide#no-trailing-array-commas'
  EnforcedStyleForMultiline: comma
  SupportedStylesForMultiline:
    - comma
    - consistent_comma
    - no_comma
  Enabled: true

Style/TrailingCommaInArrayLiteral:
  Description: 'Checks for trailing comma in array literals.'
  StyleGuide: 'https://github.com/bbatsov/ruby-style-guide#no-trailing-array-commas'
  EnforcedStyleForMultiline: comma
  SupportedStylesForMultiline:
    - comma
    - consistent_comma
    - no_comma
  Enabled: true

Gemfile

source "https://rubygems.org"
#
# touch .rubocop.yml .rubocop-rspec.yml .rubocop-rails.yml
#
# Add gems to your Gemfile
group :development, :test do 
  gem "rubocop-rails"
  gem "rubocop-rspec"
  gem "rubocop-performance"
  gem "standard", "~> 1.3"
end