Do these views actually do anything? I wonder if this is better fixed on the Python side - i.e. don't attempt to display a widget unless there's something it can display.

I cannot think of a use case where you would really want to display a bare empty view. This is just to avoid an error on the JavaScript when display is called implicitly.
It might be simpler than an ad hoc solution on the python side to avoid display to do anything for widgets whose view names is one of those.

I guess my fix more specifically would be: set view_name to an empty string instead of something like 'WidgetView' (which isn't really a view, just a base class). And then in Widget._ipython_display_(), do nothing if view_name is empty.

Ok, it makes sense. ( Although then calling Widget() still raises an error on the JavaScript side :) )

Actually we could do both, I find it conceptually annoying that widgets with no views are "displayed".

What error would Widget() raise on the JS side? Can't it instantiate the model without a view name?

Oh you also want Widget to have no view? Not just custom stuff like Link. Then ok.

Yeah, I'm thinking that view_name should only be set if there is a real, displayable view for the widget.

Updated as suggested by Thomas.

+1 to having a null view that actually is special and does nothing (rather than just being the default base class).

Thinking about this some more, I wonder if instantiating Widget() should actually throw an error on the Python side - Widget is effectively an Abstract Base Class, i.e. it should be used by subclassing it.

+1 to having a null view that actually is special and does nothing (rather than just being the default base class).

I'm +1 for this too, only if we decide not to persist invisible models.

Thanks!