supporting nil when passed in as an IN clause

activerecord/lib/active_record/relation/predicate_builder.rb

@@ -25,7 +25,18 @@ module ActiveRecord
             values = value.to_a.map { |x|
               x.is_a?(ActiveRecord::Base) ? x.id : x
             }
-            attribute.in(values)
+
+            if values.include?(nil)
+              values = values.compact
+              if values.empty?
+                attribute.eq nil
+              else
+                attribute.in(values.compact).or attribute.eq(nil)
+              end
+            else
+              attribute.in(values)
+            end
+
           when Range, Arel::Relation
             attribute.in(value)
           when ActiveRecord::Base

activerecord/test/cases/finder_test.rb

@@ -1045,7 +1045,7 @@ class FinderTest < ActiveRecord::TestCase
                               :order => ' author_addresses_authors.id DESC ', :limit => 3).size
   end
 
-  def test_find_with_nil_inside_set_passed_for_attribute
+  def test_find_with_nil_inside_set_passed_for_one_attribute
     client_of = Company.find(
       :all,
       :conditions => {
@@ -1054,7 +1054,8 @@ class FinderTest < ActiveRecord::TestCase
       :order => 'client_of DESC'
     ).map { |x| x.client_of }
 
-    assert_equal [2, 1, nil], client_of
+    assert client_of.include?(nil)
+    assert_equal [2, 1].sort, client_of.compact.sort
   end
 
   def test_find_with_nil_inside_set_passed_for_attribute
@@ -1064,7 +1065,7 @@ class FinderTest < ActiveRecord::TestCase
       :order => 'client_of DESC'
     ).map { |x| x.client_of }
 
-    assert_equal [nil], client_of
+    assert_equal [], client_of.compact
   end
 
   def test_with_limiting_with_custom_select