[FIX] Feature Constructor: no fail when no values

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,
@@ -292,7 +292,7 @@ def data(self, index, role=Qt.DisplayRole):
             return super().data(index, role)
 
 
-class FeatureConstructorSettingsHandler(DomainContextHandler):
+class FeatureConstructorHandler(DomainContextHandler):
     """Context handler that filters descriptors"""
 
     def is_valid_item(self, setting, descriptor, attrs, metas):
@@ -326,7 +326,7 @@ class OWFeatureConstructor(OWWidget):
 
     want_main_area = False
 
-    settingsHandler = FeatureConstructorSettingsHandler()
+    settingsHandler = FeatureConstructorHandler()
     descriptors = ContextSetting([])
     currentIndex = ContextSetting(-1)
 
@@ -850,7 +850,7 @@ def make_arg(name):
         if sys.version_info >= (3, 0):
             return ast.arg(arg=name, annotation=None)
         else:
-            return ast.Name(id=arg, ctx=ast.Param(), lineno=1, col_offset=0)
+            return ast.Name(id=name, ctx=ast.Param(), lineno=1, col_offset=0)
 
     lambda_ = ast.Lambda(
         args=ast.arguments(
@@ -902,7 +902,7 @@ def make_arg(name):
     "weibullvariate": random.weibullvariate,
     "triangular": random.triangular,
     "uniform": random.uniform}
-)
+                )
 
 
 class FeatureFunc:
@@ -930,8 +930,10 @@ def unique(seq):
     return unique_el
 
 
-def main(argv=sys.argv):
+def main(argv=None):
     from AnyQt.QtWidgets import QApplication
+    if argv is None:
+        argv = sys.argv
     app = QApplication(list(argv))
     argv = app.arguments()
     if len(argv) > 1:

Orange/widgets/data/tests/test_owfeatureconstructor.py

@@ -11,11 +11,10 @@
 from Orange.widgets.data.owfeatureconstructor import (DiscreteDescriptor,
                                                       ContinuousDescriptor,
                                                       StringDescriptor,
-                                                      construct_variables, OWFeatureConstructor)
+                                                      construct_variables, OWFeatureConstructor,
+                                                      DiscreteFeatureEditor)
 
-from Orange.widgets.data.owfeatureconstructor import (
-    freevars, make_lambda, validate_exp
-)
+from Orange.widgets.data.owfeatureconstructor import freevars, validate_exp
 
 import dill as pickle  # Import dill after Orange because patched
 
@@ -99,11 +98,11 @@ class PicklingTest(unittest.TestCase):
     def test_lambdas_pickle(self):
         NONLOCAL_CONST = 5
 
-        lambda_func = lambda x, LOCAL_CONST=7: \
-            x * LOCAL_CONST * NONLOCAL_CONST * self.CLASS_CONST * GLOBAL_CONST
+        lambda_func = lambda x, local_const=7: \
+            x * local_const * NONLOCAL_CONST * self.CLASS_CONST * GLOBAL_CONST
 
-        def nested_func(x, LOCAL_CONST=7):
-            return x * LOCAL_CONST * NONLOCAL_CONST * self.CLASS_CONST * GLOBAL_CONST
+        def nested_func(x, local_const=7):
+            return x * local_const * NONLOCAL_CONST * self.CLASS_CONST * GLOBAL_CONST
 
         self.assertEqual(lambda_func(11),
                          pickle.loads(pickle.dumps(lambda_func))(11))
@@ -240,3 +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())