lib/rubocop/cop/style/symbol_proc.rb


# frozen_string_literal: true

module RuboCop
  module Cop
    module Style
      # Use symbols as procs when possible.
      #
      # @example
      #   # bad
      #   something.map { |s| s.upcase }
      #   something.map { _1.upcase }
      #
      #   # good
      #   something.map(&:upcase)
      class SymbolProc < Base
        include RangeHelp
        include IgnoredMethods
        extend AutoCorrector

        MSG = 'Pass `&:%<method>s` as an argument to `%<block_method>s` ' \
              'instead of a block.'
        SUPER_TYPES = %i[super zsuper].freeze

        def_node_matcher :proc_node?, '(send (const {nil? cbase} :Proc) :new)'
        def_node_matcher :symbol_proc?, <<~PATTERN
          ({block numblock}
            ${(send ...) (super ...) zsuper}
            ${(args (arg _)) %Integer}
            (send (lvar _var) $_))
        PATTERN

        def self.autocorrect_incompatible_with
          [Layout::SpaceBeforeBlockBraces]
        end

        def on_block(node)
          symbol_proc?(node) do |dispatch_node, arguments_node, method_name|
            # TODO: Rails-specific handling that we should probably make
            # configurable - https://github.com/rubocop-hq/rubocop/issues/1485
            # we should ignore lambdas & procs
            return if proc_node?(dispatch_node)
            return if %i[lambda proc].include?(dispatch_node.method_name)
            return if ignored_method?(dispatch_node.method_name)
            return if node.block_type? && destructuring_block_argument?(arguments_node)

            register_offense(node, method_name, dispatch_node.method_name)
          end
        end
        alias on_numblock on_block

        def destructuring_block_argument?(argument_node)
          argument_node.one? && argument_node.source.include?(',')
        end

        private

        def register_offense(node, method_name, block_method_name)
          block_start = node.loc.begin.begin_pos
          block_end = node.loc.end.end_pos
          range = range_between(block_start, block_end)
          message = format(MSG, method: method_name, block_method: block_method_name)

          add_offense(range, message: message) do |corrector|
            autocorrect(corrector, node)
          end
        end

        def autocorrect(corrector, node)
          if node.send_node.arguments?
            autocorrect_with_args(corrector, node, node.send_node.arguments, node.body.method_name)
          else
            autocorrect_without_args(corrector, node)
          end
        end

        def autocorrect_without_args(corrector, node)
          corrector.replace(block_range_with_space(node),
                            "(&:#{node.body.method_name})")
        end

        def autocorrect_with_args(corrector, node, args, method_name)
          arg_range = args.last.source_range
          arg_range = range_with_surrounding_comma(arg_range, :right)
          replacement = " &:#{method_name}"
          replacement = ",#{replacement}" unless arg_range.source.end_with?(',')
          corrector.insert_after(arg_range, replacement)
          corrector.remove(block_range_with_space(node))
        end

        def block_range_with_space(node)
          block_range = range_between(begin_pos_for_replacement(node),
                                      node.loc.end.end_pos)
          range_with_surrounding_space(range: block_range, side: :left)
        end

        def begin_pos_for_replacement(node)
          expr = node.send_node.source_range

          if (paren_pos = (expr.source =~ /\(\s*\)$/))
            expr.begin_pos + paren_pos
          else
            node.loc.begin.begin_pos
          end
        end
      end
    end
  end
end