name_for_action

# File actionpack/lib/action_dispatch/routing/mapper.rb, line 1437
          def name_for_action(as, action) #:nodoc:
            prefix = prefix_name_for_action(as, action)
            prefix = Mapper.normalize_name(prefix) if prefix
            name_prefix = @scope[:as]

            if parent_resource
              return nil if as.nil? && action.nil?

              collection_name = parent_resource.collection_name
              member_name = parent_resource.member_name
            end

            name = case @scope[:scope_level]
            when :nested
              [name_prefix, prefix]
            when :collection
              [prefix, name_prefix, collection_name]
            when :new
              [prefix, :new, name_prefix, member_name]
            when :member
              [prefix, shallow_scoping? ? @scope[:shallow_prefix] : name_prefix, member_name]
            when :root
              [name_prefix, collection_name, prefix]
            else
              [name_prefix, member_name, prefix]
            end

            candidate = name.select(&:present?).join("_").presence
            candidate unless as.nil? && @set.routes.find { |r| r.name == candidate }
          end