fix(z3cformdoc): One can't change widget factories in update() any more

[do3cc]

When using autoform, the widgets get initialized before the update
method is run. Therefore one must override the widgetFactory in updateWidgets.

Dunno if this was intended, but thats the way it works now.

[davisagli]

If you're changing this to updateWidgets, you need to call updateWidgets on the super too, or you'll get into a loop.

[hvelarde]

fixed (I guess) in 982af27

[do3cc]

@davisagli you said that calling update() in updateWidgets would make the view run in circles. That made me wonder and look more into the issue.
a z3c.form view really calls updateWidgets() from within update. In such a case I could still add another widgetfactory in an update method. But plone.autoform changed the order in which the methods get called. There updateWidgets() is called before update().

https://github.com/plone/plone.autoform/blob/master/plone/autoform/view.py#L45
https://github.com/zopefoundation/z3c.form/blob/master/src/z3c/form/form.py#L148
For me this sounds like a bug in plone.autoform. Do you agree or do I miss something?

[davisagli]

Here's the order of operations when update gets called on most autoforms:

1. self.update, which is plone.z3cform.extensible.ExtensibleForm:update unless overridden
2. self.updateFields, which is plone.autoform.form.AutoExtensibleForm:updateFields unless overridden
3. self.updateFieldsFromSchemata, which is plone.autoform.base.AutoFields:updateFieldsFromSchemata unless overridden (here's where the fields are created, and default widgets set)
4. super(AutoExtensibleForm, self).updateFields, which is usually plone.z3cform.extensible.ExtensibleForm:updateFields (this gives form extenders a chance to run; see @bosim's recent blog post)
5. super(ExtensibleForm, self).update, which is usually z3c.form.group.GroupForm:update
6. self.updateWidgets, which is z3c.form.group.GroupForm:updateWidgets unless overridden

You pointed at plone.autoform.view.WidgetsView, which is used for views (not forms) that make use of z3c.form widgets in display mode, and it works somewhat differently. It does seem wrong that it calls updateWidgets before calling update, but I guess Martin structured it this way so that it would with views that are doing their own (non-widget-related) initialization in update. Overriding updateWidgets like in this PR should still work.