Make it impossible to set event types to empty

This would result in no notifications ever being sent

docs/api.rst

@@ -713,6 +713,11 @@ Notification profile endpoints
               }
           }
 
+      .. note::
+        ``event_types`` cannot be ``null`` or ``[]``, because all events have an event
+        type set, which would therefore result in no notifications ever being sent.
+        For not filtering by ``event_types`` the key needs to be removed.
+
 
 -  ``/api/v1/notificationprofiles/filters/<int:pk>/``:
 
@@ -1490,6 +1495,11 @@ Notification profile endpoints
               }
           }
 
+      .. note::
+        ``event_types`` cannot be ``null`` or ``[]``, because all events have an event
+        type set, which would therefore result in no notifications ever being sent.
+        For not filtering by ``event_types`` the key needs to be removed.
+
 
 -  ``/api/v2/notificationprofiles/filters/<int:pk>/``:
 

src/argus/notificationprofile/primitive_serializers.py

@@ -31,6 +31,11 @@ class FilterBlobSerializer(serializers.Serializer):
         required=False,
     )
 
+    def validate_event_types(self, value):
+        if not value:
+            raise serializers.ValidationError("Event types cannot be empty, remove it completely from filter instead.")
+        return value
+
 
 class FilterPreviewSerializer(serializers.Serializer):
     sourceSystemIds = serializers.ListField(child=serializers.IntegerField(min_value=1), allow_empty=True)

tests/notificationprofile/test_views.py

@@ -403,6 +403,17 @@ def test_should_create_filter_with_event_types(self):
         self.assertEqual(response.status_code, status.HTTP_201_CREATED)
         self.assertTrue(Filter.objects.filter(pk=response.data["pk"]).exists())
 
+    def test_should_not_create_filter_with_empty_event_types(self):
+        filter_name = "test-filter"
+        response = self.user1_rest_client.post(
+            path=self.ENDPOINT,
+            data={
+                "name": filter_name,
+                "filter": {"event_types": []},
+            },
+        )
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+
     def test_should_update_filter_name_with_valid_values(self):
         filter1_pk = self.filter1.pk
         filter1_path = f"{self.ENDPOINT}{filter1_pk}/"