class RuboCop::Cop::Performance::Detect

This cop is used to identify usages of `select.first`, `select.last`, `find_all.first`, and `find_all.last` and change them to use `detect` instead.

@example

# bad
[].select { |item| true }.first
[].select { |item| true }.last
[].find_all { |item| true }.first
[].find_all { |item| true }.last

# good
[].detect { |item| true }
[].reverse.detect { |item| true }

`ActiveRecord` compatibility: `ActiveRecord` does not implement a `detect` method and `find` has its own meaning. Correcting ActiveRecord methods with this cop should be considered unsafe.

Constants

MSG
REVERSE_MSG

Public Instance Methods

autocorrect(node) click to toggle source
# File lib/rubocop/cop/performance/detect.rb, line 54
def autocorrect(node)
  receiver, first_method = *node

  replacement = if first_method == :last
                  "reverse.#{preferred_method}"
                else
                  preferred_method
                end

  first_range = receiver.source_range.end.join(node.loc.selector)

  receiver, _args, _body = *receiver if receiver.block_type?

  lambda do |corrector|
    corrector.remove(first_range)
    corrector.replace(receiver.loc.selector, replacement)
  end
end
on_send(node) click to toggle source
# File lib/rubocop/cop/performance/detect.rb, line 40
def on_send(node)
  return if rails_safe_mode?

  detect_candidate?(node) do |receiver, second_method, args|
    return unless args.empty?
    return unless receiver

    receiver, _args, body = *receiver if receiver.block_type?
    return if accept_first_call?(receiver, body)

    register_offense(node, receiver, second_method)
  end
end

Private Instance Methods

accept_first_call?(receiver, body) click to toggle source
# File lib/rubocop/cop/performance/detect.rb, line 75
def accept_first_call?(receiver, body)
  caller, _first_method, args = *receiver

  # check that we have usual block or block pass
  return true if body.nil? && (args.nil? || !args.block_pass_type?)

  lazy?(caller)
end
lazy?(node) click to toggle source
# File lib/rubocop/cop/performance/detect.rb, line 101
def lazy?(node)
  return false unless node

  receiver, method, _args = *node
  method == :lazy && !receiver.nil?
end
preferred_method() click to toggle source
# File lib/rubocop/cop/performance/detect.rb, line 96
def preferred_method
  config.for_cop('Style/CollectionMethods') \
    ['PreferredMethods']['detect'] || 'detect'
end
register_offense(node, receiver, second_method) click to toggle source
# File lib/rubocop/cop/performance/detect.rb, line 84
def register_offense(node, receiver, second_method)
  _caller, first_method, _args = *receiver
  range = receiver.loc.selector.join(node.loc.selector)

  message = second_method == :last ? REVERSE_MSG : MSG
  formatted_message = format(message, prefer: preferred_method,
                                      first_method: first_method,
                                      second_method: second_method)

  add_offense(node, location: range, message: formatted_message)
end