implementing where_sql method

lib/arel/select_manager.rb

@@ -122,6 +122,13 @@ module Arel
       Compatibility::Wheres.new @engine, @ctx.wheres
     end
 
+    def where_sql
+      return if @ctx.wheres.empty?
+
+      viz = Visitors::WhereSql.new @engine
+      Nodes::SqlLiteral.new viz.accept @ctx
+    end
+
     def take limit
       @head.limit = limit
       self

lib/arel/visitors.rb

@@ -3,6 +3,7 @@ require 'arel/visitors/postgresql'
 require 'arel/visitors/mysql'
 require 'arel/visitors/oracle'
 require 'arel/visitors/join_sql'
+require 'arel/visitors/where_sql'
 require 'arel/visitors/order_clauses'
 require 'arel/visitors/dot'
 

spec/select_manager_spec.rb

@@ -379,6 +379,23 @@ module Arel
       end
     end
 
+    describe 'where_sql' do
+      it 'gives me back the where sql' do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new Table.engine
+        manager.from table
+        manager.where table[:id].eq 10
+        manager.where_sql.should be_like %{ WHERE "users"."id" = 10 }
+      end
+
+      it 'returns nil when there are no wheres' do
+        table   = Table.new :users
+        manager = Arel::SelectManager.new Table.engine
+        manager.from table
+        manager.where_sql.should be_nil
+      end
+    end
+
     describe 'update' do
       it 'copies limits' do
         engine  = EngineProxy.new Table.engine