feat: allow opt-out of schema dump to dict

- Adds `payload_schema_dump: bool = True` arg to `dispatch`, `_derive_event_name_and_payload_from_pydantic_model` and `_validate_payload`. When `False`, the event handlers are called "live" pydantic model for payload. The default behaviour is unchanged.
- Updates tests for this new functionality.

Closes melvinkcx#56

fastapi_events/dispatcher.py

@@ -110,7 +110,8 @@ def _derive_event_name_and_payload_from_pydantic_model(
     event_name_or_model: Union[EventName, PydanticModel],
     event_name: EventName,
     payload: Payload,
-    payload_schema_cls_dict_args: Dict[str, Any]
+    payload_schema_cls_dict_args: Dict[str, Any],
+    payload_schema_dump: bool
 ):
     """
     Derive event_name and payload from Pydantic model
@@ -123,7 +124,10 @@ def _derive_event_name_and_payload_from_pydantic_model(
 
     if not payload:
         payload_schema_cls_dict_args = payload_schema_cls_dict_args or DEFAULT_PAYLOAD_SCHEMA_CLS_DICT_ARGS
-        payload = event_name_or_model.dict(**payload_schema_cls_dict_args)
+        if payload_schema_dump:
+            payload = event_name_or_model.dict(**payload_schema_cls_dict_args)
+        else:
+            payload = event_name_or_model
 
     return event_name, payload
 
@@ -132,7 +136,8 @@ def _validate_payload(
     event_name: EventName,
     payload: Payload,
     payload_schema_registry: BaseEventPayloadSchemaRegistry,
-    payload_schema_cls_dict_args: Dict[str, Any]
+    payload_schema_cls_dict_args: Dict[str, Any],
+    payload_schema_dump: bool = True
 ):
     """
     Validate payload if a corresponding payload schema is registered
@@ -143,10 +148,14 @@ def _validate_payload(
     payload_schema_cls = payload_schema_registry.get(event_name)
     if payload_schema_cls:
         payload_schema_cls_dict_args = payload_schema_cls_dict_args or DEFAULT_PAYLOAD_SCHEMA_CLS_DICT_ARGS
-        if IS_PYDANTIC_V1:
-            payload = payload_schema_cls(**(payload or {})).dict(**payload_schema_cls_dict_args)
+        deserialized_payload = payload_schema_cls(**(payload or {}))
+        if payload_schema_dump:
+            if IS_PYDANTIC_V1:
+                payload = deserialized_payload.dict(**payload_schema_cls_dict_args)
+            else:
+                payload = deserialized_payload.model_dump(**payload_schema_cls_dict_args)
         else:
-            payload = payload_schema_cls(**(payload or {})).model_dump(**payload_schema_cls_dict_args)
+            payload = deserialized_payload
     else:
         logger.debug("Payload schema for event %s not found. Skipping validation...", event_name)
 
@@ -160,7 +169,8 @@ def dispatch(
     validate_payload: bool = True,
     payload_schema_cls_dict_args: Optional[Dict[str, Any]] = None,
     payload_schema_registry: Optional[BaseEventPayloadSchemaRegistry] = None,
-    middleware_id: Optional[int] = None
+    middleware_id: Optional[int] = None,
+    payload_schema_dump: bool = True
 ) -> None:
     """
     A wrapper of the main dispatcher function with additional checks.
@@ -181,7 +191,8 @@ def dispatch(
                     event_name_or_model=event_name_or_model,
                     event_name=event_name,
                     payload=payload,
-                    payload_schema_cls_dict_args=payload_schema_cls_dict_args
+                    payload_schema_cls_dict_args=payload_schema_cls_dict_args,
+                    payload_schema_dump=payload_schema_dump,
                 )
 
             # Validate event payload with schema registered
@@ -191,7 +202,8 @@ def dispatch(
                     event_name=event_name,
                     payload=payload,
                     payload_schema_registry=payload_schema_registry,
-                    payload_schema_cls_dict_args=payload_schema_cls_dict_args
+                    payload_schema_cls_dict_args=payload_schema_cls_dict_args,
+                    payload_schema_dump=payload_schema_dump
                 )
 
         # OTEL

tests/test_dispatcher.py

@@ -68,8 +68,12 @@ async def test_suppression_of_events_in_req_res_cycle(
      ({"user_id": uuid.uuid4()}, True),
      ({}, True),
      (None, True)))
+@pytest.mark.parametrize(
+    "payload_schema_dump",
+    (True, False)
+)
 async def test_payload_validation_with_pydantic_in_req_res_cycle(
-    event_payload, should_raise_error, setup_mocks_for_events_in_req_res_cycle
+    event_payload, should_raise_error, payload_schema_dump, setup_mocks_for_events_in_req_res_cycle,
 ):
     """
     Test if event payloads are properly validated when a payload schema is registered.
@@ -88,7 +92,8 @@ class _SignUpEventSchema(pydantic.BaseModel):
     dispatch_fn = functools.partial(dispatch,
                                     event_name=UserEvents.SIGNED_UP,
                                     payload=event_payload,
-                                    payload_schema_registry=payload_schema)
+                                    payload_schema_registry=payload_schema,
+                                    payload_schema_dump=payload_schema_dump)
 
     if should_raise_error:
         with pytest.raises(pydantic.ValidationError):
@@ -100,8 +105,12 @@ class _SignUpEventSchema(pydantic.BaseModel):
 
 
 @pytest.mark.asyncio
+@pytest.mark.parametrize(
+    "payload_schema_dump",
+    (True, False)
+)
 async def test_dispatching_with_pydantic_model(
-    setup_mocks_for_events_in_req_res_cycle, mocker
+    payload_schema_dump, setup_mocks_for_events_in_req_res_cycle, mocker
 ):
     payload_schema = EventPayloadSchemaRegistry()
 
@@ -114,12 +123,14 @@ class UserSignedUpEventSchema(pydantic.BaseModel):
 
         username: str
 
-    dispatch(UserSignedUpEventSchema(username="USER_ABC"))
+    event = UserSignedUpEventSchema(username="USER_ABC")
+    expected_payload = {"username": "USER_ABC"} if payload_schema_dump else event
+    dispatch(event, payload_schema_dump=payload_schema_dump)
 
     assert mocks["spy_event_store_ctx_var"].get.called
     spy__dispatch.assert_called_with(
         event_name="USER_SIGNED_UP",
-        payload={"username": "USER_ABC"}
+        payload=expected_payload
     )