generators can't be @collection_default_content

[Barry Warsaw]

If you define a function like this:

(in the interface):

    @collection_default_content()
    def __iter__():
        """Iterate over all mailing lists."""

(in the content object):

    def __iter__(self):
        """See `IListManager`."""
        for mailing_list in self.mailing_lists:
            yield mailing_list

You get the following error:

TypeError: ('Could not adapt', <generator object __iter__ at 0x1efab70>, <InterfaceClass zope.interface.common.sequence.IFiniteSequence>)

which makes sense, because you don't know if a generator is a finite sequence. Still, I think it would be nice if generators could somehow be supported, as most of them /are/ finite.

[Leonard Richardson (leonardr)]

I've run into a similar problem. That cast is happening because we're trying to find the length of the sequence. I believe I can change lazr.batchnavigator to support batching objects with no __len__, at the expense of performance.