Fix #count on a has_many :through association so that it recognizes the :uniq...

Fix #count on a has_many :through association so that it recognizes the :uniq option.  Closes #8801 [lifofifo]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@7199 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

 *SVN*
 
+* Fix #count on a has_many :through association so that it recognizes the :uniq option.  Closes #8801 [lifofifo]
+
 * Fix and properly document/test count(column_name) usage. Closes #8999 [lifofifo]
 
 * Remove deprecated count(conditions=nil, joins=nil) usage.  Closes #8993 [lifofifo]

activerecord/lib/active_record/associations/has_many_through_association.rb

@@ -100,6 +100,16 @@ def create!(attrs = nil)
       def sum(*args, &block)
         calculate(:sum, *args, &block)
       end
+      
+      def count(*args)
+        column_name, options = @reflection.klass.send(:construct_count_options_from_args, *args)
+        if @reflection.options[:uniq]
+          # This is needed becase 'SELECT count(DISTINCT *)..' is not valid sql statement.
+          column_name = "#{@reflection.klass.table_name}.#{@reflection.klass.primary_key}" if column_name == :all
+          options.merge!(:distinct => true) 
+        end
+        @reflection.klass.send(:with_scope, construct_scope) { @reflection.klass.count(column_name, options) } 
+      end
 
       protected
         def method_missing(method, *args, &block)

activerecord/test/associations/join_model_test.rb

@@ -30,7 +30,16 @@ def test_has_many_uniq_through_join_model
     assert_equal 2, authors(:mary).categorized_posts.size
     assert_equal 1, authors(:mary).unique_categorized_posts.size
   end
-
+  
+  def test_has_many_uniq_through_count
+    author = authors(:mary)
+    assert !authors(:mary).unique_categorized_posts.loaded?
+    assert_queries(1) { assert_equal 1, author.unique_categorized_posts.count }
+    assert_queries(1) { assert_equal 1, author.unique_categorized_posts.count(:title) }
+    assert_queries(1) { assert_equal 0, author.unique_categorized_posts.count(:title, :conditions => "title is NULL") }
+    assert !authors(:mary).unique_categorized_posts.loaded?
+  end
+  
   def test_polymorphic_has_many
     assert posts(:welcome).taggings.include?(taggings(:welcome_general))
   end