[Zope-CMF] small proposal, catalog tool

[computing project]

Hi,

I'd like to change the way that the catalog is implemented slightly, to 
allow tools other than the workflow tool to provide variables to the 
catalog.  I'm happy to submit the code + tests if everyone's 
happy/interested.

1.  Provide a new interface.  Currently, only the workflow tool implements 
this interface

class ICatalogVariableProvider(Interface):

  def getCatalogVariablesFor(obj):
     """Return a dictionary of additional properties to be made available to
         the catalog when an object is indexed
     """
     return vars

2.  Change the catalog tool to something like:

      def catalog_object(self, obj, uid, idxs=None, update_metadata=1):
        vars = {}
        for tool in self._providers:
           pt = getToolByName(obj, tool, None)
           if pt:
              vars.update( pt.getCatalogVariablesFor( obj ) )

        w = IndexableObjectWrapper(vars, obj)
        ZCatalog.catalog_object(self, w, uid, idxs, update_metadata)

      where at the moment, _providers would be just a one-item tuple ( 
'portal_workflow', )

This way it's much easier to hook other tools in at indexing time by adding 
them to the list, rather than needing to create a new catalog class.  (note 
this code is a rough cut-and-paste, so it might well have typos - for 
illustration only!)

Any thoughts?  Is this useful?

pete

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