[Zope3-dev] RFC: Make <widget /> subdirective support sequence/items widgets

[Philipp von Weitershausen]

Hi there,

it's quite confusing that sequence widgets and items widgets (such as 
SelectWidget, DropdownWidget, etc.) cannot be specified in the <widget 
/> subdirective of the addform and editform directives. I actually 
consider it a bug because documentation and implementation are saying 
something different. Rather than changing the documentation by limiting 
the use of <widget /> to the simple form fields, I have added changed 
the directive handler to support both sequence widgets and vocabulary 
widgets on the philikon-widget-subdirective branch.

The idea of the change is the following:

Normal widgets's __init__ take (field, request) like a regular browser 
view. Sequence widgets take (field, value_type, request) because they 
are multiviews for (field, value_type) and vocabulary widgets take 
(field, vocabulary, request) because they are multiviews for (field, 
vocabulary).

I have created a CustomVocabularyWidgetFactory like 
CustomSequenceWidgetFactory. All factories, including 
CustomWidgetFactory, comply with the IViewFactory interface, however 
(which means their __call__ takes (context, request)). That means that 
API backward compatability with CustomSequenceWidgetFactory is broken. 
However, since the latter was only introduced on the trunk recently, I 
would think it's ok to break it. I also think API conformity is to be 
valued highly here.

I have also created two new interfaces, ISequenceWidgetFactory and 
IVocabularyWidgetFactory. The sequence widget classes *provide* the 
former, the vocabulary widget classes *provide* the latter (not 
implement!). Now, when you use the <widget /> directive, it chooses 
either CustomSequenceWidgetFactory or CustomVocabularyWidgetFactory 
according to which interface the given widget class provides. That way, 
widget classes are always called with the right number of arguments when 
<widget /> is used.


I have implemented these changes on a branch because they break API 
backward compabatility on CustomSequenceWidgetFactory. Before I merge 
these changes, I would like to hear your comments, especially from 
people who are heavily involved into forms (Roger, Garret, ...?). Given 
no objections, I can merge anytime. The branch is ready.

Thanks,

Philipp