[FIX] OWSom: Fix crash for data without class variable

[Anamari-ctrl]

Issue

Fixes #6750

Description of changes

Fixed TypeError: 'DiscreteVariable' object is not iterable.

Includes

• Code changes
• Tests
• Documentation

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[janezd]

Also, rename the PR to "[FIX] OWSom: Fix crash for data without class variable".

In description, replace Bugs in SOM #6750 with Fixes #6750, which will automatically close #6750 when PR is merged.

[janezd]

Please remove the above. We consider Domain immutable, so class_vars must not be changed, neither is there any need to change them because that already equal ().

[janezd]

You must not do this. widget.data is a data table, and widget.data.domain describes its columns. By removing classes, the table and its domain are inconsistent, and anything can happen. (Also. domain is internally inconsistent because when class_var is not None, class_vars equals (class_var, ).)

Instead, you must construct a new domain and convert the table.

        data = self.iris.transform(Domain(self.iris.domain.attributes))
        self.send_signal(self.widget.Inputs.data, data)

The first line creates a new data table without class, and the second line sends it to the widget. Then you can remove widget.update_output().

[janezd]

This doesn't test much. You may want to test two things. First, if you want to test that the widget no longer crashes, this line is unnecessary -- it would crash in the previous line (prior to your fix). But a better test would be that the widget constructs a correct domain. The proper test is

    def test_make_domain_without_class_vars(self):
        widget = self.widget
        data = self.iris.transform(Domain(self.iris.domain.attributes))
        self.send_signal(self.widget.Inputs.data, data)

        domain = self.get_output((widget.Outputs.annotated_data)).domain
        self.assertEqual(domain.attributes, data.domain.attributes)
        self.assertEqual(domain.class_var.name, ANNOTATED_DATA_FEATURE_NAME)
        self.assertEqual([var.name for var in domain.metas],
                         ["som_cell", "som_row", "som_col", "som_error"])

[janezd]

You incorrectly copied the test that I suggested. Please fix the indent.

[codecov]

Codecov Report

Merging #6763 (2a3427d) into master (88fae8a) will decrease coverage by 0.01%.
Report is 12 commits behind head on master.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6763      +/-   ##
==========================================
- Coverage   88.15%   88.15%   -0.01%     
==========================================
  Files         323      323              
  Lines       70747    70748       +1     
==========================================
- Hits        62369    62368       -1     
- Misses       8378     8380       +2