lib/rubocop/cop/style/rescue_modifier.rb


# frozen_string_literal: true

module RuboCop
  module Cop
    module Style
      # This cop checks for uses of rescue in its modifier form.
      #
      # The cop to check `rescue` in its modifier form is added for following
      # reasons:
      #
      # * The syntax of modifier form `rescue` can be misleading because it
      #   might led us to believe that `rescue` handles the given exception
      #   but it actually rescue all exceptions to return the given rescue
      #   block. In this case, value returned by handle_error or
      #   SomeException.
      #
      # * Modifier form `rescue` would rescue all the exceptions. It would
      #   silently skip all exception or errors and handle the error.
      #   Example: If `NoMethodError` is raised, modifier form rescue would
      #   handle the exception.
      #
      # @example
      #   # bad
      #   some_method rescue handle_error
      #
      #   # bad
      #   some_method rescue SomeException
      #
      #   # good
      #   begin
      #     some_method
      #   rescue
      #     handle_error
      #   end
      #
      #   # good
      #   begin
      #     some_method
      #   rescue SomeException
      #     handle_error
      #   end
      class RescueModifier < Cop
        include Alignment
        include RescueNode

        MSG = 'Avoid using `rescue` in its modifier form.'

        def on_resbody(node)
          return unless rescue_modifier?(node)

          add_offense(node.parent)
        end

        def autocorrect(node)
          parenthesized = parenthesized?(node)
          lambda do |corrector|
            corrector.replace(node, corrected_block(node, parenthesized))
            ParenthesesCorrector.correct(corrector, node.parent) if parenthesized
          end
        end

        private

        def parenthesized?(node)
          node.parent && parentheses?(node.parent)
        end

        def corrected_block(node, parenthesized)
          operation, rescue_modifier, = *node
          *_, rescue_args = *rescue_modifier

          node_indentation, node_offset = indentation_and_offset(node, parenthesized)

          "begin\n" \
            "#{operation.source.gsub(/^/, node_indentation)}" \
            "\n#{node_offset}rescue\n" \
            "#{rescue_args.source.gsub(/^/, node_indentation)}" \
            "\n#{node_offset}end"
        end

        def indentation_and_offset(node, parenthesized)
          node_indentation = indentation(node)
          node_offset = offset(node)
          if parenthesized
            node_indentation = node_indentation[0...-1]
            node_offset = node_offset[0...-1]
          end
          [node_indentation, node_offset]
        end
      end
    end
  end
end