[FIX] OWEditDomain: Clear editor when data is disconnected

[aturanjanin]

Issue

Fixes #4483

Includes

• Code changes
• Tests
• Documentation

[codecov]

Codecov Report

Merging #4484 into master will increase coverage by 0.22%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #4484      +/-   ##
==========================================
+ Coverage   83.16%   83.39%   +0.22%     
==========================================
  Files         268      274       +6     
  Lines       54001    55077    +1076     
==========================================
+ Hits        44911    45930    +1019     
- Misses       9090     9147      +57     

[janezd]

Nice. It's a small glitch, but we should tolerate them.

I don't entirely like the fix, though. It relies on the left-hand listview sending an (essentially invalid) signal that something (in fact: nothing) has been selected. The solution is thus based on a side-effect.

I think this should be explicitly handled by OWEditDomain.clear whose job is to clean up the widget. I suppose OWEditDomain.clear should call self._editor.clear(), where ReinterpretVariableEditor.clear would probably be defined as:

    def clear(self):
        self.layout().currentWidget().clear()

This seems to work, but please check - in particular for any crashes for different current widgets. (Can current widget be None or something else that doesn't have clear?)

Also think whether ReinterpretVariableEditor.clear also needs to do something else. Also check that the corresponding widget's clear methods do everything they need to to clean their houses.

[janezd]

Line 1: "should": I meant "shouldn't"! :)

[aturanjanin]

What if we add self.layout().currentWidget().clear() call into the already existing function OWEditDomain.clear_editor and call that function in the OWEditDomain.clear, would that be a fine solution maybe?
Also, current widget can only be one of four - Discrete/Continuous/Time/Variable Editor.

[janezd]

OK, you can do so, too, I guess.