Merge pull request #253 from RasaHQ/extract-slots-helper

add helper to extract form slot candidates

changelog/238.feature.rst

@@ -0,0 +1,32 @@
+Added the method ``form_slots_to_validate`` to ``Tracker``. This method is helpful
+when using a custom action to validate slots which were extracted by a Form as shown
+by the following example.
+
+.. code-block:: python
+
+    class ValidateSlots(Action):
+        def name(self) -> Text:
+            return "validate_your_form"
+
+        def run(
+            self, dispatcher: CollectingDispatcher, tracker: Tracker, domain: Dict
+        ) -> List[EventType]:
+            extracted_slots: Dict[Text, Any] = tracker.form_slots_to_validate()
+
+            validation_events = []
+
+            for slot_name, slot_value in extracted_slots:
+                # Check if slot is valid.
+                if is_valid(slot_value):
+                    validation_events.append(SlotSet(slot_name, slot_value))
+                else:
+                    # Return a `SlotSet` event with value `None` to indicate that this
+                    # slot still needs to be filled.
+                    validation_events.append(SlotSet(slot_name, None))
+
+            return validation_events
+
+        def is_valid(slot_value: Any) -> bool:
+            # Implementation of the validate function.
+
+ Please note that ``tracker.form_slots_to_validate`` only works with Rasa Open Source 2.

rasa_sdk/interfaces.py

@@ -228,6 +228,34 @@ def undo_till_previous(event_type: Text, done_events: List[Dict[Text, Any]]):
                 applied_events.append(event)
         return applied_events
 
+    def form_slots_to_validate(self) -> Dict[Text, Any]:
+        """Get form slots which need validation.
+
+        You can use a custom action to validate slots which were extracted during the
+        latest form execution. This method provides you all extracted candidates for
+        form slots.
+
+        Returns:
+            A mapping of extracted slot candidates and their values.
+        """
+
+        slots_to_validate = {}
+
+        if not self.active_loop:
+            return slots_to_validate
+
+        for event in reversed(self.events):
+            # The `FormAction` in Rasa Open Source will append all slot candidates
+            # at the end of the tracker events.
+            if event["event"] == "slot":
+                slots_to_validate[event["name"]] = event["value"]
+            else:
+                # Stop as soon as there is another event type as this means that we
+                # checked all potential slot candidates.
+                break
+
+        return slots_to_validate
+
 
 class Action:
     """Next action to be taken in response to a dialogue state."""

tests/test_tracker.py

@@ -1,5 +1,7 @@
+import pytest
+
 from rasa_sdk import Tracker
-from rasa_sdk.events import ActionExecuted, UserUttered, ActionReverted
+from rasa_sdk.events import ActionExecuted, UserUttered, ActionReverted, SlotSet
 from rasa_sdk.interfaces import ACTION_LISTEN_NAME
 from typing import List, Dict, Text, Any
 
@@ -70,3 +72,42 @@ def test_last_executed_has_not_name():
     tracker = get_tracker(events)
 
     assert tracker.last_executed_action_has("another") is False
+
+
+@pytest.mark.parametrize(
+    "events, expected_extracted_slots",
+    [
+        ([], {}),
+        ([ActionExecuted("my_form")], {}),
+        (
+            [ActionExecuted("my_form"), SlotSet("my_slot", "some_value")],
+            {"my_slot": "some_value"},
+        ),
+        (
+            [
+                ActionExecuted("my_form"),
+                SlotSet("my_slot", "some_value"),
+                SlotSet("some_other", "some_value2"),
+            ],
+            {"my_slot": "some_value", "some_other": "some_value2"},
+        ),
+        ([SlotSet("my_slot", "some_value"), ActionExecuted("my_form")], {},),
+    ],
+)
+def test_get_extracted_slots(
+    events: List[Dict[Text, Any]], expected_extracted_slots: Dict[Text, Any]
+):
+    tracker = get_tracker(events)
+    tracker.active_loop = {"name": "my form"}
+    assert tracker.form_slots_to_validate() == expected_extracted_slots
+
+
+def test_get_extracted_slots_with_no_active_loop():
+    events = [
+        ActionExecuted("my_form"),
+        SlotSet("my_slot", "some_value"),
+        SlotSet("some_other", "some_value2"),
+    ]
+    tracker = get_tracker(events)
+
+    assert tracker.form_slots_to_validate() == {}