1 files changed, 60 insertions, 0 deletions
diff --git a/activerecord/lib/arel/nodes/node.rb b/activerecord/lib/arel/nodes/node.rb
new file mode 100644
index 0000000000..2b9b1e9828
--- /dev/null
+++ b/activerecord/lib/arel/nodes/node.rb
@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    ###
+    # Abstract base class for all AST nodes
+    class Node
+      include Arel::FactoryMethods
+      include Enumerable
+
+      if $DEBUG
+        def _caller
+          @caller
+        end
+
+        def initialize
+          @caller = caller.dup
+        end
+      end
+
+      ###
+      # Factory method to create a Nodes::Not node that has the recipient of
+      # the caller as a child.
+      def not
+        Nodes::Not.new self
+      end
+
+      ###
+      # Factory method to create a Nodes::Grouping node that has an Nodes::Or
+      # node as a child.
+      def or(right)
+        Nodes::Grouping.new Nodes::Or.new(self, right)
+      end
+
+      ###
+      # Factory method to create an Nodes::And node.
+      def and(right)
+        Nodes::And.new [self, right]
+      end
+
+      # FIXME: this method should go away.  I don't like people calling
+      # to_sql on non-head nodes.  This forces us to walk the AST until we
+      # can find a node that has a "relation" member.
+      #
+      # Maybe we should just use `Table.engine`?  :'(
+      def to_sql(engine = Table.engine)
+        collector = Arel::Collectors::SQLString.new
+        collector = engine.connection.visitor.accept self, collector
+        collector.value
+      end
+
+      # Iterate through AST, nodes will be yielded depth-first
+      def each(&block)
+        return enum_for(:each) unless block_given?
+
+        ::Arel::Visitors::DepthFirst.new(block).accept self
+      end
+    end
+  end
+end