literal_as_condition.rb

# frozen_string_literal: true

module RuboCop
  module Cop
    module Lint
      # Checks for literals used as the conditions or as
      # operands in and/or expressions serving as the conditions of
      # if/while/until/case-when/case-in.
      #
      # NOTE: Literals in `case-in` condition where the match variable is used in
      # `in` are accepted as a pattern matching.
      #
      # @example
      #
      #   # bad
      #   if 20
      #     do_something
      #   end
      #
      #   # bad
      #   if some_var && true
      #     do_something
      #   end
      #
      #   # good
      #   if some_var && some_condition
      #     do_something
      #   end
      #
      #   # good
      #   # When using a boolean value for an infinite loop.
      #   while true
      #     break if condition
      #   end
      class LiteralAsCondition < Base
        include RangeHelp

        MSG = 'Literal `%<literal>s` appeared as a condition.'

        def on_if(node)
          check_for_literal(node)
        end

        def on_while(node)
          return if condition(node).true_type?

          check_for_literal(node)
        end
        alias on_while_post on_while

        def on_until(node)
          return if condition(node).false_type?

          check_for_literal(node)
        end
        alias on_until_post on_until

        def on_case(case_node)
          if case_node.condition
            check_case(case_node)
          else
            case_node.each_when do |when_node|
              next unless when_node.conditions.all?(&:literal?)

              range = when_conditions_range(when_node)
              message = message(range)

              add_offense(range, message: message)
            end
          end
        end

        def on_case_match(case_match_node)
          if case_match_node.condition
            return if case_match_node.descendants.any?(&:match_var_type?)

            check_case(case_match_node)
          else
            case_match_node.each_in_pattern do |in_pattern_node|
              next unless in_pattern_node.condition.literal?

              add_offense(in_pattern_node)
            end
          end
        end

        def on_send(node)
          return unless node.negation_method?

          check_for_literal(node)
        end

        def message(node)
          format(MSG, literal: node.source)
        end

        private

        def check_for_literal(node)
          cond = condition(node)
          if cond.literal?
            add_offense(cond)
          else
            check_node(cond)
          end
        end

        def basic_literal?(node)
          if node.array_type?
            primitive_array?(node)
          else
            node.basic_literal?
          end
        end

        def primitive_array?(node)
          node.children.all? { |n| basic_literal?(n) }
        end

        def check_node(node)
          if node.send_type? && node.prefix_bang?
            handle_node(node.receiver)
          elsif node.operator_keyword?
            node.each_child_node { |op| handle_node(op) }
          elsif node.begin_type? && node.children.one?
            handle_node(node.children.first)
          end
        end

        def handle_node(node)
          if node.literal?
            add_offense(node)
          elsif %i[send and or begin].include?(node.type)
            check_node(node)
          end
        end

        def check_case(case_node)
          condition = case_node.condition

          return if condition.array_type? && !primitive_array?(condition)
          return if condition.dstr_type?

          handle_node(condition)
        end

        def condition(node)
          if node.send_type?
            node.receiver
          else
            node.condition
          end
        end

        def when_conditions_range(when_node)
          range_between(
            when_node.conditions.first.source_range.begin_pos,
            when_node.conditions.last.source_range.end_pos
          )
        end
      end
    end
  end
end