trailing_comma_in_attribute_declaration.rb

# frozen_string_literal: true

module RuboCop
  module Cop
    module Lint
      # This cop checks for trailing commas in attribute declarations, such as
      # `#attr_reader`. Leaving a trailing comma will nullify the next method
      # definition by overriding it with a getter method.
      #
      # @example
      #
      #   # bad
      #   class Foo
      #     attr_reader :foo,
      #
      #     def bar
      #       puts "Unreachable."
      #     end
      #   end
      #
      #   # good
      #   class Foo
      #     attr_reader :foo
      #
      #     def bar
      #       puts "No problem!"
      #     end
      #   end
      #
      class TrailingCommaInAttributeDeclaration < Base
        extend AutoCorrector
        include RangeHelp

        MSG = 'Do not use trailing comma in attribute declarations.'

        def on_send(node)
          return unless node.attribute_accessor? && node.arguments.last.def_type?

          trailing_comma = trailing_comma_range(node)

          add_offense(trailing_comma) do |corrector|
            corrector.remove(trailing_comma)
          end
        end

        private

        def trailing_comma_range(node)
          range_with_surrounding_space(
            range: node.arguments[-2].source_range,
            side: :right
          ).end.resize(1)
        end
      end
    end
  end
end