more select manager tests passing

lib/arel/visitors/depth_first.rb

@@ -5,11 +5,22 @@ module Arel
         @block = block || Proc.new
       end
 
+      def accept object
+        visit object
+      end
+
       private
 
-      def visit o
-        super
-        @block.call o
+      def visit object
+        send dispatch[object.class], object
+      rescue NoMethodError => e
+        raise e if respond_to?(dispatch[object.class], true)
+        superklass = object.class.ancestors.find { |klass|
+          respond_to?(dispatch[klass], true)
+        }
+        raise(TypeError, "Cannot visit #{object.class}") unless superklass
+        dispatch[object.class] = dispatch[superklass]
+        retry
       end
 
       def unary o

lib/arel/visitors/to_sql.rb

@@ -280,12 +280,14 @@ module Arel
         "WITH #{o.children.map { |x| visit x }.join(', ')}"
       end
 
-      def visit_Arel_Nodes_WithRecursive o
-        "WITH RECURSIVE #{o.children.map { |x| visit x }.join(', ')}"
+      def visit_Arel_Nodes_WithRecursive o, collector
+        collector << "WITH RECURSIVE "
+        inject_join o.children, collector, ', '
       end
 
-      def visit_Arel_Nodes_Union o
-        "( #{visit o.left} UNION #{visit o.right} )"
+      def visit_Arel_Nodes_Union o, collector
+        collector << "( "
+        infix_value(o, collector, " UNION ") << " )"
       end
 
       def visit_Arel_Nodes_UnionAll o
@@ -296,7 +298,7 @@ module Arel
         "( #{visit o.left} INTERSECT #{visit o.right} )"
       end
 
-      def visit_Arel_Nodes_Except o
+      def visit_Arel_Nodes_Except o, collector
         "( #{visit o.left} EXCEPT #{visit o.right} )"
       end
 
@@ -393,8 +395,8 @@ module Arel
         collector
       end
 
-      def visit_Arel_Nodes_Lock o
-        visit o.expr
+      def visit_Arel_Nodes_Lock o, collector
+        visit o.expr, collector
       end
 
       def visit_Arel_Nodes_Grouping o, collector
@@ -522,16 +524,19 @@ module Arel
         raise NotImplementedError, '!~ not implemented for this db'
       end
 
-      def visit_Arel_Nodes_StringJoin o
-        visit o.left
+      def visit_Arel_Nodes_StringJoin o, collector
+        visit o.left, collector
       end
 
       def visit_Arel_Nodes_FullOuterJoin o
         "FULL OUTER JOIN #{visit o.left} #{visit o.right}"
       end
 
-      def visit_Arel_Nodes_OuterJoin o
-        "LEFT OUTER JOIN #{visit o.left} #{visit o.right}"
+      def visit_Arel_Nodes_OuterJoin o, collector
+        collector << "LEFT OUTER JOIN "
+        collector = visit o.left, collector
+        collector << " "
+        visit o.right, collector
       end
 
       def visit_Arel_Nodes_RightOuterJoin o
@@ -735,6 +740,12 @@ module Arel
         }
       end
 
+      def infix_value o, collector, value
+        collector = visit o.left, collector
+        collector << " UNION "
+        visit o.right, collector
+      end
+
       def aggregate name, o, collector
         collector << "#{name}("
         if o.distinct

test/test_select_manager.rb

@@ -369,8 +369,9 @@ module Arel
         table   = Table.new :users
         mgr = table.from table
         ast = mgr.ast
-        mgr.visitor.accept(ast).must_equal mgr.to_sql
+        assert ast
       end
+
       it 'should allow orders to work when the ast is grepped' do
         table   = Table.new :users
         mgr = table.from table