handle deletions correctly

owrx/property/__init__.py

@@ -322,11 +322,13 @@ class PropertyStack(PropertyManager):
 
     def receiveEvent(self, layer, changes):
         changesToForward = {name: value for name, value in changes.items() if layer == self._getTopLayer(name)}
-        # deletions need to be handled separately: only send them if deleted in all layers
+        # deletions need to be handled separately:
+        # * send a deletion if the key was deleted in all layers
+        # * send lower value if the key is still present in a lower layer
         deletionsToForward = {
-            name: value
+            name: PropertyDeleted if self._getTopLayer(name, False) is None else self[name]
             for name, value in changes.items()
-            if value is PropertyDeleted and self._getTopLayer(name, False) is None
+            if value is PropertyDeleted
         }
         self._fireCallbacks({**changesToForward, **deletionsToForward})
 

test/property/test_property_stack.py

@@ -215,3 +215,14 @@ class PropertyStackTest(TestCase):
         ps.wire(mock.method)
         del low_pm["testkey"]
         mock.method.assert_called_once_with({"testkey": PropertyDeleted})
+
+    def testChangeEventWhenKeyDeleted(self):
+        ps = PropertyStack()
+        low_pm = PropertyLayer(testkey="lowvalue")
+        high_pm = PropertyLayer(testkey="highvalue")
+        ps.addLayer(0, high_pm)
+        ps.addLayer(1, low_pm)
+        mock = Mock()
+        ps.wire(mock.method)
+        del high_pm["testkey"]
+        mock.method.assert_called_once_with({"testkey": "lowvalue"})