join_constraints

# File activerecord/lib/active_record/associations/join_dependency.rb, line 81
      def join_constraints(joins_to_add, alias_tracker, references)
        @alias_tracker = alias_tracker
        @joined_tables = {}
        @references = {}

        references.each do |table_name|
          @references[table_name.to_sym] = table_name if table_name.is_a?(Arel::Nodes::SqlLiteral)
        end unless references.empty?

        joins = make_join_constraints(join_root, join_type)

        joins.concat joins_to_add.flat_map { |oj|
          if join_root.match? oj.join_root
            walk(join_root, oj.join_root, oj.join_type)
          else
            make_join_constraints(oj.join_root, oj.join_type)
          end
        }
      end