Fixed ID partitioning interpolation, when cloning attachments

lib/paperclip/interpolations.rb

@@ -150,10 +150,13 @@ module Paperclip
     # Returns the id of the instance in a split path form. e.g. returns
     # Returns the id of the instance in a split path form. e.g. returns
     # 000/001/234 for an id of 1234.
     # 000/001/234 for an id of 1234.
     def id_partition attachment, style_name
     def id_partition attachment, style_name
-      if (id = attachment.instance.id).is_a?(Integer)
+      case id = attachment.instance.id
+      when Integer
         ("%09d" % id).scan(/\d{3}/).join("/")
         ("%09d" % id).scan(/\d{3}/).join("/")
-      else
+      when String
         id.scan(/.{3}/).first(3).join("/")
         id.scan(/.{3}/).first(3).join("/")
+      else
+        nil
       end
       end
     end
     end
 
 

test/interpolations_test.rb

@@ -88,6 +88,13 @@ class InterpolationsTest < Test::Unit::TestCase
     assert_equal 23, Paperclip::Interpolations.id(attachment, :style)
     assert_equal 23, Paperclip::Interpolations.id(attachment, :style)
   end
   end
 
 
+  should "return nil for attachments to new records" do
+    attachment = mock
+    attachment.expects(:id).returns(nil)
+    attachment.expects(:instance).returns(attachment)
+    assert_nil Paperclip::Interpolations.id(attachment, :style)
+  end
+
   should "return the partitioned id of the attachment when the id is an integer" do
   should "return the partitioned id of the attachment when the id is an integer" do
     attachment = mock
     attachment = mock
     attachment.expects(:id).returns(23)
     attachment.expects(:id).returns(23)
@@ -102,6 +109,13 @@ class InterpolationsTest < Test::Unit::TestCase
     assert_equal "32f/nj2/3oi", Paperclip::Interpolations.id_partition(attachment, :style)
     assert_equal "32f/nj2/3oi", Paperclip::Interpolations.id_partition(attachment, :style)
   end
   end
 
 
+  should "return nil for the partitioned id of an attachment to a new record (when the id is nil)" do
+    attachment = mock
+    attachment.expects(:id).returns(nil)
+    attachment.expects(:instance).returns(attachment)
+    assert_nil Paperclip::Interpolations.id_partition(attachment, :style)
+  end
+
   should "return the name of the attachment" do
   should "return the name of the attachment" do
     attachment = mock
     attachment = mock
     attachment.expects(:name).returns("file")
     attachment.expects(:name).returns("file")