[Zope-CMF] [dev] using zope.formlib - a proposal

[yuppie]

Hi!


CMF 2.0 ships with some view based forms. They use their own framework 
and are explicitly labeled as experimental.

CMF 2.1 depends on Zope 2.10, so zope.formlib is now available. I 
propose to replace the view based forms using zope.formlib.


This is the approach I propose:


The interfaces of classic CMF content objects are not suitable for 
zope.formlib:

- Text fields are encoded strings while zope.formlib expects unicode.

- Datetime fields are Zope DateTime objects while zope.formlib expects 
generic datetime objects.

- Tuples or lists are used for unordered collections while zope.formlib 
expects Set fields.

- Different setter and getter methods are used while zope.formlib 
expects properties.

I propose to add suitable schemas in the browser packages and to use 
adapters to map the form schemas to the existing content interfaces.

I have a ProxyFieldProperty class (similar to zope.schema's 
FieldProperty class) that does the necessary mapping. This is how it is 
used for a CMFCalendar Event::


   class EventSchemaAdapter(SchemaAdapterBase):

       """Adapter for IMutableEvent.
       """

       adapts(IMutableEvent)
       implements(IEventSchema)

       title = ProxyFieldProperty(IEventSchema['title'],
                                  'Title', 'setTitle')
       contact_name = ProxyFieldProperty(IEventSchema['contact_name'])
       location = ProxyFieldProperty(IEventSchema['location'])
       contact_email = ProxyFieldProperty(IEventSchema['contact_email'])
       categories = ProxyFieldProperty(IEventSchema['categories'],
                                       'Subject', 'setSubject')
       contact_phone = ProxyFieldProperty(IEventSchema['contact_phone'])
       event_url = ProxyFieldProperty(IEventSchema['event_url'])
       start_date = ProxyFieldProperty(IEventSchema['start_date'],
                                       'start', 'setStartDate')
       stop_date = ProxyFieldProperty(IEventSchema['stop_date'],
                                      'end', 'setEndDate')
       description = ProxyFieldProperty(IEventSchema['description'],
                                        'Description', 'setDescription')

Maybe my ProxyFieldProperty implementation does too much magic at the 
moment. I expect it has to evolve over time, adding a way to control the 
mapping better.


If we have that adapter in place we can use zope.formlib in the generic 
way::

   class EventEditView(ContentEditFormBase):

       """Edit view for IMutableEvent.
       """

       form_fields = form.FormFields(IEventSchema)


Some CMF specific base classes are needed for this. I propose to add 
them in CMFDefault.formlib.

I have working code for IMutableEvent, IMutableFavorite and 
IMutableLink. I can't promise to convert the other forms.


Any feedback is welcome.


Cheers,

	Yuppie