Fix Traceback when undoing changes in URL widget

spine_items/data_store/commands.py

@@ -51,6 +51,7 @@ def mergeWith(self, command):
             not isinstance(command, UpdateDSURLCommand)
             or self._ds_name != command._ds_name
             or command._undo_url_is_valid
+            or set(self._redo_kwargs.keys()).isdisjoint(command._redo_kwargs.keys())
         ):
             return False
         diff_key = None

tests/data_store/test_commands.py

@@ -0,0 +1,42 @@
+######################################################################################################################
+# Copyright (C) 2017-2022 Spine project consortium
+# Copyright Spine Items contributors
+# This file is part of Spine Items.
+# Spine Items is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General
+# Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option)
+# any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+# without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
+# Public License for more details. You should have received a copy of the GNU Lesser General Public License along with
+# this program. If not, see <http://www.gnu.org/licenses/>.
+######################################################################################################################
+import unittest
+from unittest import mock
+from spine_items.data_store.commands import UpdateDSURLCommand
+
+
+class TestUpdateDSURLCommand(unittest.TestCase):
+    def test_merging_with_command_that_modifies_same_fields_works(self):
+        mock_ds = mock.MagicMock()
+        mock_ds.url.return_value = {"username": "c"}
+        mock_project = mock.MagicMock()
+        mock_project.get_item.return_value = mock_ds
+        command1 = UpdateDSURLCommand("DS 1", False, mock_project, username="ca")
+        mock_ds.url.return_value = {"username": "ca"}
+        command2 = UpdateDSURLCommand("DS 1", False, mock_project, username="cat")
+        self.assertTrue(command1.mergeWith(command2))
+        command1.redo()
+        mock_ds.do_update_url.assert_called_once_with(username="cat")
+
+    def test_merging_is_rejected_when_commands_modify_different_fields(self):
+        mock_ds = mock.MagicMock()
+        mock_ds.url.return_value = {"username": "c", "host": ""}
+        mock_project = mock.MagicMock()
+        mock_project.get_item.return_value = mock_ds
+        command1 = UpdateDSURLCommand("DS 1", False, mock_project, username="ca")
+        mock_ds.url.return_value = {"username": "ca", "host": ""}
+        command2 = UpdateDSURLCommand("DS 1", False, mock_project, host="q")
+        self.assertFalse(command1.mergeWith(command2))
+
+
+if __name__ == "__main__":
+    unittest.main()