Adding SqlLiteral with spec for counts

lib/arel/engines/sql/primitives.rb

@@ -1,4 +1,14 @@
 module Arel
+  class SqlLiteral < String
+    def relation
+      nil
+    end
+
+    def to_sql(formatter = nil)
+      self
+    end
+  end
+
   class Attribute
     def column
       original_relation.column_for(self)

spec/arel/engines/sql/unit/primitives/literal_spec.rb

@@ -0,0 +1,23 @@
+require File.join(File.dirname(__FILE__), '..', '..', '..', '..', '..', 'spec_helper')
+
+module Arel
+  describe SqlLiteral do
+    before do
+      @relation = Table.new(:users)
+    end
+
+    describe '#to_sql' do
+      it "manufactures sql with a literal SQL fragment" do
+        sql = @relation.project(Count.new(SqlLiteral.new("*"))).to_sql
+
+        adapter_is :mysql do
+          sql.should be_like(%Q{SELECT COUNT(*) AS count_id FROM `users`})
+        end
+
+        adapter_is_not :mysql do
+          sql.should be_like(%Q{SELECT COUNT(*) AS count_id FROM "users"})
+        end
+      end
+    end
+  end
+end