Test & Score deepcopy problem

[gpstmp]

Orange version

3.7.1

Expected behavior

I expect that Test & Score widget will work ok with Recommendations add-on widget (this model was working ok in prev versions of Orange, but produces an error after update).

Actual behavior

I have this error in logs:

----------------------------- TypeError Exception -----------------------------
Traceback (most recent call last):
  File "/Applications/Orange3.app/Contents/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/Orange/canvas/scheme/widgetsscheme.py", line 842, in process_signals_for_widget
    widget.handleNewSignals()
  File "/Applications/Orange3.app/Contents/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/Orange/widgets/evaluate/owtestlearners.py", line 486, in handleNewSignals
    self.__update()
  File "/Applications/Orange3.app/Contents/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/Orange/widgets/evaluate/owtestlearners.py", line 786, in __update
    learners_c = [copy.deepcopy(learner) for learner in learners]
  File "/Applications/Orange3.app/Contents/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/Orange/widgets/evaluate/owtestlearners.py", line 786, in <listcomp>
    learners_c = [copy.deepcopy(learner) for learner in learners]
  File "/Applications/Orange3.app/Contents/Frameworks/Python.framework/Versions/3.6/lib/python3.6/copy.py", line 180, in deepcopy
    y = _reconstruct(x, memo, *rv)
  File "/Applications/Orange3.app/Contents/Frameworks/Python.framework/Versions/3.6/lib/python3.6/copy.py", line 280, in _reconstruct
    state = deepcopy(state, memo)
  File "/Applications/Orange3.app/Contents/Frameworks/Python.framework/Versions/3.6/lib/python3.6/copy.py", line 150, in deepcopy
    y = copier(x, memo)
  File "/Applications/Orange3.app/Contents/Frameworks/Python.framework/Versions/3.6/lib/python3.6/copy.py", line 240, in _deepcopy_dict
    y[deepcopy(key, memo)] = deepcopy(value, memo)
  File "/Applications/Orange3.app/Contents/Frameworks/Python.framework/Versions/3.6/lib/python3.6/copy.py", line 150, in deepcopy
    y = copier(x, memo)
  File "/Applications/Orange3.app/Contents/Frameworks/Python.framework/Versions/3.6/lib/python3.6/copy.py", line 247, in _deepcopy_method
    return type(x)(x.__func__, deepcopy(x.__self__, memo))
  File "/Applications/Orange3.app/Contents/Frameworks/Python.framework/Versions/3.6/lib/python3.6/copy.py", line 169, in deepcopy
    rv = reductor(4)
TypeError: can't pickle OWSVDPlusPlus objects
-------------------------------------------------------------------------------

Steps to reproduce the behavior

You can download a simple example here
problem.zip

Additional info (worksheets, data, screenshots, ...)

[kernc]

Seems like Orange3-recommendation problem. I get:

PicklingError: Can't pickle <class 'Orange.widgets.utils.owlearnerwidget.Outputs'>: attribute lookup Outputs on Orange.widgets.utils.owlearnerwidget failed

[kernc]

@gpstmp Would you care enough to help us migrate recommender add-on's widgets to use new-style signals in a pull request?

[astaric]

The core problem is that (one of the) learners in c_learners holds a reference to the widget it was constructed with. This is a bad thing, but as @kernc said, a problem in orange3-recommendation add-on.

I have opened a new issue on that repository, let's move the discussion there.