rubocop-numbered-params

A RuboCop plugin that recommends using numbered parameters (_1, _2, ...) instead of named block arguments in single-line blocks.

Add the gem to your application's Gemfile:

bundle add rubocop-numbered-params

Or install it directly:

gem install rubocop-numbered-params

Then add it to your .rubocop.yml:

plugins:
  - rubocop-numbered-params

Recommends using numbered parameters (_1, _2, ...) instead of named block arguments in single-line blocks. This cop supports autocorrection.

Bad:

users.map { |user| user.name }
items.select { |item| item.active? }

Good:

users.map { _1.name }
items.select { _1.active? }

Multi-line blocks are not targeted:

# good - multi-line block (not targeted)
users.map do |user|
  user.name
end

Example with MaxArguments: 2:

Style/PreferNumberedParameter:
  MaxArguments: 2

# bad
hash.each { |key, value| "#{key}: #{value}" }

# good
hash.each { "#{_1}: #{_2}" }

The cop does not register an offense in the following cases:

• Multi-line blocks
• Blocks with an empty body
• Blocks with destructuring arguments: |(key, value)|
• Blocks with splat arguments: |*args|
• Blocks with block arguments: |&block|
• Blocks with shadow variables: |item; temp|
• Outer blocks that contain inner blocks (the inner block is checked separately)

• Ruby >= 3.2.0
• RuboCop >= 1.72.1

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/tk0miya/rubocop-numbered-params. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the rubocop-numbered-params project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.