[FIX] Feature Constructor: no fail when no values

https://sentry.io/biolab/orange3/issues/279049068/

Author: jerneju

Orange/widgets/data/owfeatureconstructor.py

@@ -244,7 +244,7 @@ def setEditorData(self, data, domain):
     def editorData(self):
         values = self.valuesedit.text()
         values = re.split(r"(?<!\\),", values)
-        values = tuple(v.replace(r"\,", ",").strip() for v in values)
+        values = tuple(filter(None, [v.replace(r"\,", ",").strip() for v in values]))
         return DiscreteDescriptor(
             name=self.nameedit.text(),
             values=values,

Orange/widgets/data/tests/test_owfeatureconstructor.py

@@ -11,7 +11,8 @@
 from Orange.widgets.data.owfeatureconstructor import (DiscreteDescriptor,
                                                       ContinuousDescriptor,
                                                       StringDescriptor,
-                                                      construct_variables, OWFeatureConstructor)
+                                                      construct_variables, OWFeatureConstructor,
+                                                      DiscreteFeatureEditor)
 
 from Orange.widgets.data.owfeatureconstructor import freevars, validate_exp
 
@@ -238,3 +239,22 @@ def test_error_invalid_expression(self):
         )
         self.widget.apply()
         self.assertTrue(self.widget.Error.invalid_expressions.is_shown())
+
+    def test_discrete_no_values(self):
+        """
+        Should not fail when there are no values set.
+        GH-2417
+        """
+        data = Table("iris")
+        self.widget.setData(data)
+        discreteFeatureEditor = DiscreteFeatureEditor()
+
+        discreteFeatureEditor.valuesedit.setText("")
+        discreteFeatureEditor.nameedit.setText("D1")
+        discreteFeatureEditor.expressionedit.setText("iris")
+        self.widget.addFeature(
+            discreteFeatureEditor.editorData()
+        )
+        self.assertFalse(self.widget.Error.more_values_needed.is_shown())
+        self.widget.apply()
+        self.assertTrue(self.widget.Error.more_values_needed.is_shown())