Do not run post_processing if the attachment is not valid.

lib/paperclip/attachment.rb

@@ -83,7 +83,7 @@ module Paperclip
 
 
       @dirty = true
       @dirty = true
 
 
-      post_process
+      post_process if valid?
  
  
       # Reset the file size if the original file was reprocessed.
       # Reset the file size if the original file was reprocessed.
       instance_write(:file_size, uploaded_file.size.to_i)
       instance_write(:file_size, uploaded_file.size.to_i)

test/attachment_test.rb

@@ -163,6 +163,7 @@ class AttachmentTest < Test::Unit::TestCase
       @attachment.expects(:valid_assignment?).with(@not_file).returns(true)
       @attachment.expects(:valid_assignment?).with(@not_file).returns(true)
       @attachment.expects(:queue_existing_for_delete)
       @attachment.expects(:queue_existing_for_delete)
       @attachment.expects(:post_process)
       @attachment.expects(:post_process)
+      @attachment.expects(:valid?).returns(true)
       @attachment.expects(:validate)
       @attachment.expects(:validate)
       @dummy.avatar = @not_file
       @dummy.avatar = @not_file
     end
     end
@@ -192,6 +193,7 @@ class AttachmentTest < Test::Unit::TestCase
       @attachment.expects(:valid_assignment?).with(@not_file).returns(true)
       @attachment.expects(:valid_assignment?).with(@not_file).returns(true)
       @attachment.expects(:queue_existing_for_delete)
       @attachment.expects(:queue_existing_for_delete)
       @attachment.expects(:post_process)
       @attachment.expects(:post_process)
+      @attachment.expects(:valid?).returns(true)
       @attachment.expects(:validate)
       @attachment.expects(:validate)
       @dummy.avatar = @not_file
       @dummy.avatar = @not_file
     end
     end

test/integration_test.rb

@@ -209,7 +209,7 @@ class IntegrationTest < Test::Unit::TestCase
       @dummy.avatar = @bad_file
       @dummy.avatar = @bad_file
       assert ! @dummy.valid?
       assert ! @dummy.valid?
       @dummy.avatar = nil
       @dummy.avatar = nil
-      assert @dummy.valid?
+      assert @dummy.valid?, @dummy.errors.inspect 
     end
     end
 
 
     should "know the difference between good files, bad files, not files, and nil when validating" do
     should "know the difference between good files, bad files, not files, and nil when validating" do