Disallow dialogue stack slot from being set in custom actions & mark builtin slots

rasa/core/actions/action.py

@@ -37,6 +37,7 @@
 )
 from rasa.shared.core import events
 from rasa.shared.core.constants import (
+    DIALOGUE_STACK_SLOT,
     USER_INTENT_OUT_OF_SCOPE,
     ACTION_LISTEN_NAME,
     ACTION_RESTART_NAME,
@@ -829,6 +830,13 @@ async def run(
             )
 
             evts = events.deserialise_events(events_json)
+            # filter out `SlotSet` events for internal `dialogue_stack` slot
+            evts = [
+                event
+                for event in evts
+                if not (isinstance(event, SlotSet) and event.key == DIALOGUE_STACK_SLOT)
+            ]
+
             return cast(List[Event], bot_messages) + evts
 
         except ClientResponseError as e:

rasa/shared/core/domain.py

@@ -993,7 +993,12 @@ def _add_flow_slots(self) -> None:
         for flow_slot in FLOW_SLOT_NAMES:
             if flow_slot not in slot_names:
                 self.slots.append(
-                    AnySlot(flow_slot, mappings=[], influence_conversation=False)
+                    AnySlot(
+                        flow_slot,
+                        mappings=[],
+                        influence_conversation=False,
+                        is_builtin=True,
+                    )
                 )
             else:
                 # TODO: figure out what to do here.
@@ -1016,6 +1021,7 @@ def _add_requested_slot(self) -> None:
                     rasa.shared.core.constants.REQUESTED_SLOT,
                     mappings=[],
                     influence_conversation=False,
+                    is_builtin=True,
                 )
             )
 
@@ -1041,12 +1047,21 @@ def _add_knowledge_base_slots(self) -> None:
             for slot in KNOWLEDGE_BASE_SLOT_NAMES:
                 if slot not in slot_names:
                     self.slots.append(
-                        TextSlot(slot, mappings=[], influence_conversation=False)
+                        TextSlot(
+                            slot,
+                            mappings=[],
+                            influence_conversation=False,
+                            is_builtin=True,
+                        )
                     )
 
     def _add_session_metadata_slot(self) -> None:
         self.slots.append(
-            AnySlot(rasa.shared.core.constants.SESSION_START_METADATA_SLOT, mappings=[])
+            AnySlot(
+                rasa.shared.core.constants.SESSION_START_METADATA_SLOT,
+                mappings=[],
+                is_builtin=True,
+            )
         )
 
     def index_for_action(self, action_name: Text) -> int:

rasa/shared/core/slots.py

@@ -35,6 +35,7 @@ def __init__(
         initial_value: Any = None,
         value_reset_delay: Optional[int] = None,
         influence_conversation: bool = True,
+        is_builtin: bool = False,
     ) -> None:
         """Create a Slot.
 
@@ -46,6 +47,9 @@ def __init__(
                 initial_value. This is behavior is currently not implemented.
             influence_conversation: If `True` the slot will be featurized and hence
                 influence the predictions of the dialogue polices.
+            is_builtin: `True` if the slot is a built-in slot, `False` otherwise.
+                Built-in slots also encompass user writable slots (via custom actions),
+                such as `return_value`.
         """
         self.name = name
         self.mappings = mappings
@@ -54,6 +58,7 @@ def __init__(
         self._value_reset_delay = value_reset_delay
         self.influence_conversation = influence_conversation
         self._has_been_set = False
+        self.is_builtin = is_builtin
 
     def feature_dimensionality(self) -> int:
         """How many features this single slot creates.
@@ -180,6 +185,7 @@ def __init__(
         max_value: float = 1.0,
         min_value: float = 0.0,
         influence_conversation: bool = True,
+        is_builtin: bool = False,
     ) -> None:
         """Creates a FloatSlot.
 
@@ -188,7 +194,12 @@ def __init__(
             UserWarning, if initial_value is outside the min-max range.
         """
         super().__init__(
-            name, mappings, initial_value, value_reset_delay, influence_conversation
+            name,
+            mappings,
+            initial_value,
+            value_reset_delay,
+            influence_conversation,
+            is_builtin,
         )
         self.max_value = max_value
         self.min_value = min_value
@@ -318,10 +329,16 @@ def __init__(
         initial_value: Any = None,
         value_reset_delay: Optional[int] = None,
         influence_conversation: bool = True,
+        is_builtin: bool = False,
     ) -> None:
         """Creates a `Categorical  Slot` (see parent class for detailed docstring)."""
         super().__init__(
-            name, mappings, initial_value, value_reset_delay, influence_conversation
+            name,
+            mappings,
+            initial_value,
+            value_reset_delay,
+            influence_conversation,
+            is_builtin,
         )
         if values and None in values:
             rasa.shared.utils.io.raise_warning(
@@ -417,6 +434,7 @@ def __init__(
         initial_value: Any = None,
         value_reset_delay: Optional[int] = None,
         influence_conversation: bool = False,
+        is_builtin: bool = False,
     ) -> None:
         """Creates an `Any  Slot` (see parent class for detailed docstring).
 
@@ -433,7 +451,12 @@ def __init__(
             )
 
         super().__init__(
-            name, mappings, initial_value, value_reset_delay, influence_conversation
+            name,
+            mappings,
+            initial_value,
+            value_reset_delay,
+            influence_conversation,
+            is_builtin,
         )
 
     def __eq__(self, other: Any) -> bool:

tests/core/test_actions.py

@@ -3039,3 +3039,25 @@ def test_default_actions_and_names_consistency():
         RULE_SNIPPET_ACTION_NAME
     }
     assert names_of_default_actions == names_of_executable_actions_in_constants
+
+
+async def test_filter_out_dialogue_stack_slot_set_in_a_custom_action(
+    default_channel: OutputChannel,
+    default_nlg: NaturalLanguageGenerator,
+    default_tracker: DialogueStateTracker,
+    domain: Domain,
+) -> None:
+    endpoint = EndpointConfig("https://example.com/webhooks/actions")
+    remote_action = action.RemoteAction("my_action", endpoint)
+    events = [SlotSet(DIALOGUE_STACK_SLOT, {}), SlotSet("some_slot", "some_value")]
+    events_as_dict = [event.as_dict() for event in events]
+    response = {"events": events_as_dict, "responses": []}
+    with aioresponses() as mocked:
+        mocked.post("https://example.com/webhooks/actions", payload=response)
+
+        events = await remote_action.run(
+            default_channel, default_nlg, default_tracker, domain
+        )
+
+    assert len(events) == 1
+    assert events[0] == SlotSet("some_slot", "some_value")

tests/shared/core/test_domain.py

@@ -23,6 +23,7 @@
 from rasa.shared.core.slots import InvalidSlotTypeException, TextSlot
 from rasa.shared.core.constants import (
     DEFAULT_INTENTS,
+    KNOWLEDGE_BASE_SLOT_NAMES,
     SLOT_LISTED_ITEMS,
     SLOT_LAST_OBJECT,
     SLOT_LAST_OBJECT_TYPE,
@@ -2371,3 +2372,12 @@ def test_domain_with_slots_without_mappings(caplog: LogCaptureFixture) -> None:
         "Slot 'slot_without_mappings' has no mappings defined. "
         "We will continue with an empty list of mappings."
     ) in caplog.text
+
+
+def test_domain_default_slots_are_marked_as_builtin(domain: Domain) -> None:
+    all_default_slot_names = DEFAULT_SLOT_NAMES.union(KNOWLEDGE_BASE_SLOT_NAMES)
+    domain_default_slots = [
+        slot for slot in domain.slots if slot.name in all_default_slot_names
+    ]
+
+    assert all(slot.is_builtin for slot in domain_default_slots)

tests/shared/core/test_slots.py

@@ -156,6 +156,10 @@ def test_slot_fingerprint_uniqueness(
         f2 = slot.fingerprint()
         assert f1 != f2
 
+    def test_slot_is_not_builtin_by_default(self, mappings: List[Dict[Text, Any]]):
+        slot = self.create_slot(mappings, influence_conversation=False)
+        assert not slot.is_builtin
+
 
 class TestTextSlot(SlotTestCollection):
     def create_slot(