adding a grouping node

lib/arel/nodes.rb

+require 'arel/nodes/node'
 require 'arel/nodes/binary'
 require 'arel/nodes/equality'
 require 'arel/nodes/not_equal'
@@ -29,6 +30,7 @@
 require 'arel/nodes/table_alias'
 require 'arel/nodes/join'
 require 'arel/nodes/group'
+require 'arel/nodes/grouping'
 require 'arel/nodes/inner_join'
 require 'arel/nodes/outer_join'
 require 'arel/nodes/string_join'

lib/arel/nodes/binary.rb

 module Arel
   module Nodes
-    class Binary
+    class Binary < Arel::Nodes::Node
       attr_accessor :left, :right
 
       def initialize left, right
@@ -8,14 +8,6 @@ def initialize left, right
         @right = right
       end
 
-      def or right
-        Nodes::Or.new self, right
-      end
-
-      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.

lib/arel/nodes/grouping.rb

+module Arel
+  module Nodes
+    class Grouping < Arel::Nodes::Node
+      attr_accessor :expr
+
+      def initialize expression
+        @expr = expression
+      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
+        viz = Visitors::ToSql.new Table.engine
+        viz.accept self
+      end
+    end
+  end
+end

lib/arel/nodes/node.rb

+module Arel
+  module Nodes
+    ###
+    # Abstract base class for all AST nodes
+    class Node
+      ###
+      # 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
+    end
+  end
+end

lib/arel/visitors/to_sql.rb

@@ -84,6 +84,10 @@ def visit_Arel_Nodes_Offset o
       def visit_Arel_Nodes_Lock o
       end
 
+      def visit_Arel_Nodes_Grouping o
+        "(#{visit o.expr})"
+      end
+
       def visit_Arel_Nodes_Group o
         visit o.expr
       end

spec/arel/nodes/equality_spec.rb

@@ -34,8 +34,8 @@ module Nodes
           left  = attr.eq(10)
           right = attr.eq(11)
           node  = left.or right
-          check node.left.should == left
-          check node.right.should == right
+          check node.expr.left.should == left
+          check node.expr.right.should == right
         end
       end
 

spec/arel/nodes/or_spec.rb

@@ -7,12 +7,12 @@ module Nodes
           left  = attr.eq(10)
           right = attr.eq(11)
           node  = left.or right
-          check node.left.should == left
-          check node.right.should == right
+          check node.expr.left.should == left
+          check node.expr.right.should == right
 
           oror = node.or(right)
-          check oror.left == node
-          check oror.right == right
+          check oror.expr.left == node
+          check oror.expr.right == right
         end
       end
     end