[Zope] OFS/Image.py strange error

[Vladimir Petrovic]

Hi,
I'm getting a very strange error during the development of my python based 
product. The error occurs only in one specific case, and the setup is quite 
complicated. The error happens inside Zope code, so I'm looking for hints how 
to proceed with debuging. The issue is that during a call to _read_data () in 
OFS/Image.py I get the following error:

KeyError: validate 

Traceback:
Module ZPublisher.Publish, line 98, in publish
Module ZPublisher.mapply, line 88, in mapply
Module ZPublisher.Publish, line 39, in call_object
Module OFS.DTMLMethod, line 135, in __call__


However, the actual _read_data () happens inside the python product, so the 
original traceback is somehow lost.

Here is the setup:
I have a python product which defines a class that inherits ObjectManager 
(called Content). I have another classes DRFile/DRImage which inherit Zope's 
File/Image.

Inside manage_addContent (), manage_addDRFIle () is called to create 
automatically new DRFile inside content:

manage_addContent ():
  co = Content (id) 
  self._setObject (id, co)
 
  co = self._getOb (id)
  co.add_part_web (default_part_id, default_part)

add_part_web (pid, pdata):
  nid, title = get_default_id_title_for_file (pid, '', pdata)
  manage_addDRFile (self, id=nid, title=title, file=pdata)

manage_addDRFile ():
  o = DRFile (id, title, '')
  self._setObject (id, o)

  if file:
    o = self._getOb (id)
    file_upload (o, file)

Now file_upload (o, file) is the problem. It used to contain just:
obj.manage_upload (file)

But this line was generating the error. If I put raise 'ABC' just before, I 
get the 'ABC' exception, but if I put it just after I get this KeyError.

I've managed to avoid this exception with:
  file_str = file.read ()
  data, size = obj._read_data (file_str)
  content_type = obj._get_content_type (file, data,
                                obj.__name__, 'application/octet-stream')

  obj.update_data (data, content_type, size)

This is exactly the code from mange_upload () from Image.py, except string is 
passed (file.read ()) to _read_data () instead of actual FileUpload object.

This error happens only in one specific case. I can upload the file manually 
through Zope management interface. I can also upload many other files without 
any problem. I could imagine something is wrong with FileUpload object, but I 
don't know how to proceed with the debugging because I don't know how it is 
possible that _read_data () produces the traceback which doesn't have 
anything in common with the way it is called ?

Thanks in advance,
Vladimir