lib/rubocop/cop/lint/duplicated_key.rb


# encoding: utf-8
# frozen_string_literal: true

module RuboCop
  module Cop
    module Lint
      # This cop checks for duplicated keys in hash literals.
      #
      # This cop mirrors a warning in Ruby 2.2.
      #
      # @example
      #   hash = { food: 'apple', food: 'orange' }
      class DuplicatedKey < Cop
        MSG = 'Duplicated key in hash literal.'.freeze

        def on_hash(node)
          keys = []

          hash_pairs = *node
          hash_pairs.each do |pair|
            key, _value = *pair
            if keys.include?(key) && key.recursive_basic_literal?
              add_offense(key, :expression)
            end
            keys << key
          end
        end
      end
    end
  end
end