Add support for ordering on expressions

Conflicts:

	lib/arel.rb
	lib/arel/attributes/attribute.rb
	lib/arel/nodes/infix_operation.rb
	lib/arel/nodes/named_function.rb

Conflicts:

	lib/arel.rb
	lib/arel/attributes/attribute.rb

6 files changed, 18 insertions, 8 deletions

diff --git a/lib/arel.rb b/lib/arel.rb
index de429f532e..bc599514e2 100644
--- a/lib/arel.rb
+++ b/lib/arel.rb
@@ -4,6 +4,7 @@ require 'arel/factory_methods'
 require 'arel/expressions'
 require 'arel/predications'
 require 'arel/math'
+require 'arel/order_predications'
 require 'arel/table'
 require 'arel/attributes'
 require 'arel/compatibility/wheres'
diff --git a/lib/arel/attributes/attribute.rb b/lib/arel/attributes/attribute.rb
index 240f224d8c..b9fd8da67e 100644
--- a/lib/arel/attributes/attribute.rb
+++ b/lib/arel/attributes/attribute.rb
@@ -3,6 +3,7 @@ module Arel
     class Attribute < Struct.new :relation, :name
       include Arel::Expressions
       include Arel::Predications
+      include Arel::OrderPredications
       include Arel::Math
 
       ###
diff --git a/lib/arel/expression.rb b/lib/arel/expression.rb
index eb2c21bfd3..3884d6ede6 100644
--- a/lib/arel/expression.rb
+++ b/lib/arel/expression.rb
@@ -1,4 +1,5 @@
 module Arel
   module Expression
+    include Arel::OrderPredications
   end
 end
diff --git a/lib/arel/nodes/sql_literal.rb b/lib/arel/nodes/sql_literal.rb
index c76a16daf1..ad0bb00484 100644
--- a/lib/arel/nodes/sql_literal.rb
+++ b/lib/arel/nodes/sql_literal.rb
@@ -3,6 +3,7 @@ module Arel
     class SqlLiteral < String
       include Arel::Expressions
       include Arel::Predications
+      include Arel::OrderPredications
     end
   end
 end
diff --git a/lib/arel/order_predications.rb b/lib/arel/order_predications.rb
new file mode 100644
index 0000000000..af163c9454
--- /dev/null
+++ b/lib/arel/order_predications.rb
@@ -0,0 +1,13 @@
+module Arel
+  module OrderPredications
+
+    def asc
+      Nodes::Ordering.new self, :asc
+    end
+
+    def desc
+      Nodes::Ordering.new self, :desc
+    end
+
+  end
+end
diff --git a/lib/arel/predications.rb b/lib/arel/predications.rb
index 7e2425e45f..08cbf16d9d 100644
--- a/lib/arel/predications.rb
+++ b/lib/arel/predications.rb
@@ -1,5 +1,6 @@
 module Arel
   module Predications
+
     def as other
       Nodes::As.new self, Nodes::SqlLiteral.new(other)
     end
@@ -152,14 +153,6 @@ module Arel
       grouping_all :lteq, others
     end
 
-    def asc
-      Nodes::Ordering.new self, :asc
-    end
-
-    def desc
-      Nodes::Ordering.new self, :desc
-    end
-
     private
 
     def grouping_any method_id, others