[Zope-CMF] modification date should not be bobobase_modification_time

[Rémi Houdaille]

Summary

   The DefaultDublinCoreImpl class in CFMDefault relies on
   bobobase_modification_time() when determining the modification
   time of an object. This is not quite appropriate,
   and I believe that using a specific attribute to store the
   modification time would be better.

Problem encountered

   I have built a simple application based on the CMF for management
   of shared information with our customers. We recently moved our
   web site from one server to another. For some reason, the move
   was made by exporting the (CMF) sites to a .zexp and importing
   it on the new Zope server.

   From then on, the modification times of all content appeared
   to be the date of the import. This not only impacts the
   information you see when looking at a specific document,
   but also makes news box and such things display the wrong list
   of objects :(

Proposed solution

   I solved the problem by modifying the DefaultDublinCoreImpl
   class and some dtml, in the following way :

   1. Use an attribute modification_date to store and retrieve
      the proper information. The modified() method relies on
      this attribute, other methods call it and I added a method
      to perform modification of the attribute.
      The modified code is shown below :

   def Date(self):
       "Dublin Core element - default date"
       # Return effective_date if set, modification date otherwise
       date = getattr(self, 'effective_date', None )
       if date is None:
           date = self.modified()
       return date.ISO()

   def ModificationDate(self):
       """
       Dublin Core element - date resource last modified.
       """
       return self.modified().ISO()

   def modified(self):
       """
       Dublin Core element - date resource last modified,
       returned as DateTime.
       """
       # keep compatibility with old instances
       # which do not have the modification_date attr
       if hasattr(self, 'modification_date'):
           return self.modification_date
       return self.bobobase_modification_time()

   def setModificationDate(self, date):
       """
       Dublin Core element - date resource was last modified
       """
       self.modification_date = self._datify(date)

   2. Modify the xxx_edit.dtml files (I was based on CMF1.1
      now it would be xxx_edit.py) so as to make a call to
      setModificationDate(DateTime.DateTime()). I also have
      specific creation script that I modified.

      I did it this way because I didn't want to modifiy the
      CMF itself (only my own application). If the modification
      was to be included in the CMF, it should where appropriate
      in the python code.

Discussion

   What do you think guys about this proposal?

   One question which comes to me is when exactly the
   modification_time should be changed: I currently do
   not change it when only metadata changes. It is not
   changed either when the object is cut/pasted somewhere.

   Another one is to call setModificationDate() at appropriate
   places in the code so that it is always kept at a correct value.

Rémi Houdaille