lib/rubocop/cop/mixin/duplication.rb
# frozen_string_literal: true
module RuboCop
module Cop
# Common functionality for dealing with duplication.
module Duplication
private
# Whether the `collection` contains any duplicates.
#
# @param [Array] collection an array to check for duplicates
# @return [Boolean] whether the array contains any duplicates
def duplicates?(collection)
collection.size > 1 && collection.size > collection.uniq.size
end
# Returns all duplicates, including the first instance of the duplicated
# elements.
#
# @param [Array] collection an array to return duplicates for
# @return [Array] all the duplicates
def duplicates(collection)
grouped_duplicates(collection).flatten
end
# Returns the consecutive duplicates, leaving out the first instance of
# the duplicated elements.
#
# @param [Array] collection an array to return consecutive duplicates for
# @return [Array] the consecutive duplicates
def consecutive_duplicates(collection)
grouped_duplicates(collection).flat_map { |items| items[1..] }
end
# Returns a hash of grouped duplicates. The key will be the first
# instance of the element, and the value an `array` of the initial
# element and all duplicate instances.
#
# @param [Array] collection an array to group duplicates for
# @return [Array] the grouped duplicates
def grouped_duplicates(collection)
collection.group_by { |item| item }.values.reject(&:one?)
end
end
end
end