output.rb

# frozen_string_literal: true

module RuboCop
  module Cop
    module Rails
      # This cop checks for the use of output calls like puts and print
      #
      # @example
      #   # bad
      #   puts 'A debug message'
      #   pp 'A debug message'
      #   print 'A debug message'
      #
      #   # good
      #   Rails.logger.debug 'A debug message'
      class Output < Base
        MSG = 'Do not write to stdout. ' \
              "Use Rails's logger if you want to log."
        RESTRICT_ON_SEND = %i[
          ap p pp pretty_print print puts binwrite syswrite write write_nonblock
        ].freeze

        def_node_matcher :output?, <<~PATTERN
          (send nil? {:ap :p :pp :pretty_print :print :puts} ...)
        PATTERN

        def_node_matcher :io_output?, <<~PATTERN
          (send
            {
              (gvar #match_gvar?)
              {(const nil? :STDOUT) (const nil? :STDERR)}
            }
            {:binwrite :syswrite :write :write_nonblock}
            ...)
        PATTERN

        def on_send(node)
          return unless (output?(node) || io_output?(node)) &&
                        node.arguments?

          add_offense(node.loc.selector)
        end

        private

        def match_gvar?(sym)
          %i[$stdout $stderr].include?(sym)
        end
      end
    end
  end
end