diff --git a/Orange/widgets/data/tests/test_owfile.py b/Orange/widgets/data/tests/test_owfile.py
index e33c8b0c574..e3292f575cd 100644
--- a/Orange/widgets/data/tests/test_owfile.py
+++ b/Orange/widgets/data/tests/test_owfile.py
@@ -171,6 +171,12 @@ def test_variable_name_change(self):
         data = self.get_output(self.widget.Outputs.data)
         self.assertIn("a", data.domain)
 
+        idx = self.widget.domain_editor.model().createIndex(3, 0)
+        self.widget.domain_editor.model().setData(idx, "d", Qt.EditRole)
+        self.widget.apply_button.click()
+        data = self.get_output(self.widget.Outputs.data)
+        self.assertIn("d", data.domain)
+
         # rename and change to text
         idx = self.widget.domain_editor.model().createIndex(4, 0)
         self.widget.domain_editor.model().setData(idx, "b", Qt.EditRole)
@@ -266,6 +272,13 @@ def test_check_column_noname(self):
         self.widget.domain_editor.model().setData(idx, "", Qt.EditRole)
         self.assertEqual(self.widget.domain_editor.model().data(idx, Qt.DisplayRole), temp)
 
+    def test_invalid_role_mode(self):
+        self.open_dataset("iris")
+        model = self.widget.domain_editor.model()
+        idx = model.createIndex(1, 0)
+        self.assertFalse(model.setData(idx, Qt.StatusTipRole, ""))
+        self.assertIsNone(model.data(idx, Qt.StatusTipRole))
+
     def test_context_match_includes_variable_values(self):
         file1 = """\
 var
diff --git a/Orange/widgets/utils/domaineditor.py b/Orange/widgets/utils/domaineditor.py
index 22940470074..1b7a47cb7dd 100644
--- a/Orange/widgets/utils/domaineditor.py
+++ b/Orange/widgets/utils/domaineditor.py
@@ -62,13 +62,14 @@ def set_variables(self, variables):
     def rowCount(self, parent):
         return 0 if parent.isValid() else len(self.variables)
 
-    def columnCount(self, parent):
+    @staticmethod
+    def columnCount(parent):
         return 0 if parent.isValid() else Column.not_valid
 
     def data(self, index, role):
         row, col = index.row(), index.column()
         val = self.variables[row][col]
-        if role == Qt.DisplayRole or role == Qt.EditRole:
+        if role in (Qt.DisplayRole, Qt.EditRole):
             if col == Column.tpe:
                 return self.type2name[val]
             if col == Column.place:
@@ -91,6 +92,7 @@ def data(self, index, role):
                 font = QFont()
                 font.setBold(True)
                 return font
+        return None
 
     def setData(self, index, value, role=Qt.EditRole):
         row, col = index.row(), index.column()
@@ -111,6 +113,7 @@ def setData(self, index, value, role=Qt.EditRole):
             # Settings may change background colors
             self.dataChanged.emit(index.sibling(row, 0), index.sibling(row, 3))
             return True
+        return False
 
     def headerData(self, i, orientation, role=Qt.DisplayRole):
         if orientation == Qt.Horizontal and role == Qt.DisplayRole and i < 4:
@@ -131,7 +134,7 @@ def __init__(self, view, items):
         self.view = view
         self.items = items
 
-    def createEditor(self, parent, option, index):
+    def createEditor(self, parent, _option, index):
         # This ugly hack closes the combo when the user selects an item
         class Combo(QComboBox):
             def __init__(self, *args):
@@ -146,6 +149,8 @@ def showPopup(self, *args):
                 super().showPopup(*args)
                 self.popup_shown = True
 
+            # Here, we need `self` from the closure
+            # pylint: disable=no-self-argument,attribute-defined-outside-init
             def hidePopup(me):
                 if me.popup_shown:
                     self.view.model().setData(
@@ -356,7 +361,7 @@ def numbers_are_round(var, col_data):
 
         # merge columns for X, Y and metas
         feats = cols[Place.feature]
-        X = self._merge(feats) if len(feats) else np.empty((len(data), 0))
+        X = self._merge(feats) if feats else np.empty((len(data), 0))
         Y = self._merge(cols[Place.class_var], force_dense=True)
         m = self._merge(cols[Place.meta], force_dense=True)
         domain = Domain(*places)
@@ -365,7 +370,8 @@ def numbers_are_round(var, col_data):
         else:
             return domain, [X, Y, m]
 
-    def _get_column(self, data, source_var, source_place):
+    @staticmethod
+    def _get_column(data, source_var, source_place):
         """ Extract column from data and preserve sparsity. """
         if source_place == Place.meta:
             col_data = data[:, source_var].metas
diff --git a/Orange/widgets/utils/tests/test_domaineditor.py b/Orange/widgets/utils/tests/test_domaineditor.py
index 84803ef1c94..c5e445cce2e 100644
--- a/Orange/widgets/utils/tests/test_domaineditor.py
+++ b/Orange/widgets/utils/tests/test_domaineditor.py
@@ -1,5 +1,4 @@
 import unittest
-from unittest.mock import Mock
 
 import numpy as np
 
@@ -8,7 +7,7 @@
 from Orange.data import DiscreteVariable, ContinuousVariable, StringVariable, \
     TimeVariable, Domain, Table
 from Orange.widgets.tests.base import GuiTest
-from Orange.widgets.utils.domaineditor import DomainEditor, Column, Place
+from Orange.widgets.utils.domaineditor import DomainEditor, Column
 
 
 class MockWidget(OWBaseWidget):