rubocop_default_args_assignment.rb

# USAGE:
#   rubocop -r ./tmp/rubocop_default_args_assignment.rb --only Style/RubocopDefaultArgsAssigmment app/
#
# Finds method definitions like `def my_thing(date = date)` which are circular references in ruby 2.3.1
# Change them to `def my_thing(date = self.date)` to maintain behaviour
#
module RuboCop
  module Cop
    module Style
      # Check if default args are circular assignments
      class RubocopDefaultArgsAssignment < Cop
        include OnMethodDef

        def on_method_def(node, _method_name, args, _body)
          args.children.each do |node|
            next unless node.type == :optarg
            next unless node.children.any? { |child| child.respond_to?(:type) && child.type == :lvar }

            left_name, right_node = node.children
            right_name, _ = right_node.children

            if left_name == right_name
              add_offense(node, :operator, "optional argument #{left_name.inspect} has a circular assignment")
            end

          end
        end

      end
    end
  end
end