Changed ActiveRecord::Base#exists? to invoke find_initial so that it is compatible with, and doesn't lose, :include scopes (references to eager loaded tables)

Signed-off-by: Michael Koziarski <michael@koziarski.com>
[#2543 state:committed]

activerecord/lib/active_record/base.rb

@@ -697,14 +697,9 @@ module ActiveRecord #:nodoc:
       #   Person.exists?(['name LIKE ?', "%#{query}%"])
       #   Person.exists?
       def exists?(id_or_conditions = {})
-        connection.select_all(
-          construct_finder_sql(
-            :select     => "#{quoted_table_name}.#{primary_key}",
-            :conditions => expand_id_conditions(id_or_conditions),
-            :limit      => 1
-          ),
-          "#{name} Exists"
-        ).size > 0
+        find_initial(
+          :select => "#{quoted_table_name}.#{primary_key}",
+          :conditions => expand_id_conditions(id_or_conditions)) ? true : false
       end
 
       # Creates an object (or multiple objects) and saves it to the database, if validations pass.

activerecord/test/cases/finder_test.rb

@@ -119,6 +119,12 @@ class FinderTest < ActiveRecord::TestCase
       Address.new(existing_address.street + "1", existing_address.city, existing_address.country))
   end
 
+  def test_exists_with_scoped_include
+    Developer.with_scope(:find => { :include => :projects, :order => "projects.name" }) do
+      assert Developer.exists?
+    end
+  end
+
   def test_find_by_array_of_one_id
     assert_kind_of(Array, Topic.find([ 1 ]))
     assert_equal(1, Topic.find([ 1 ]).length)