quoting strings from equality statements, adding to_dot

lib/arel/tree_manager.rb

@@ -7,6 +7,10 @@ def initialize engine
       @engine = engine
     end
 
+    def to_dot
+      Visitors::Dot.new.accept @head
+    end
+
     def to_sql
       viz = Visitors::ToSql.new @engine
       viz.accept @head

lib/arel/visitors/dot.rb

@@ -56,6 +56,8 @@ def visit_String o
       end
       alias :visit_Time :visit_String
       alias :visit_NilClass :visit_String
+      alias :visit_Arel_SqlLiteral :visit_String
+      alias :visit_Fixnum :visit_String
 
       def visit_Hash o
         o.each_with_index do |pair, i|
@@ -105,13 +107,17 @@ def with_node node
         @node_stack.pop
       end
 
+      def quote string
+        string.to_s.gsub('"', '\"')
+      end
+
       def to_dot
         "digraph \"ARel\" {\nnode [width=0.375,height=0.25,shape=record];\n" +
           @nodes.map { |node|
             label = "<f0>#{node.name}"
 
             node.fields.each_with_index do |field, i|
-              label << "|<f#{i + 1}>#{field}"
+              label << "|<f#{i + 1}>#{quote field}"
             end
 
             "#{node.id} [label=\"#{label}\"];"

lib/arel/visitors/to_sql.rb

@@ -57,7 +57,7 @@ def visit_Arel_Table o
       end
 
       def visit_Arel_Nodes_Equality o
-        "#{visit o.left} = #{visit o.right}"
+        "#{visit o.left} = #{quote visit o.right}"
       end
 
       def visit_Arel_Attributes_Attribute o

spec/arel/visitors/to_sql_spec.rb

@@ -12,6 +12,15 @@ module Visitors
         attr = Attributes::Time.new(@attr.relation, @attr.name, @attr.column)
         @visitor.accept attr
       end
+
+      describe 'Equality' do
+        it "should escape strings" do
+          test = @attr.eq 'Aaron Patterson'
+          @visitor.accept(test).should be_like %{
+            "users"."id" = 'Aaron Patterson'
+          }
+        end
+      end
     end
   end
 end