test case for event related vars carrying _var_data

tests/units/test_event.py

@@ -2,11 +2,18 @@ from typing import List
 
 import pytest
 
-from reflex import event
+from reflex.event import (
-from reflex.event import Event, EventHandler, EventSpec, call_event_handler, fix_events
+    Event,
+    EventChain,
+    EventHandler,
+    EventSpec,
+    call_event_handler,
+    event,
+    fix_events,
+)
 from reflex.state import BaseState
 from reflex.utils import format
-from reflex.vars.base import LiteralVar, Var
+from reflex.vars.base import Field, LiteralVar, Var, field
 
 
 def make_var(value) -> Var:
@@ -388,3 +395,28 @@ def test_event_actions_on_state():
     assert sp_handler.event_actions == {"stopPropagation": True}
     # should NOT affect other references to the handler
     assert not handler.event_actions
+
+
+def test_event_var_data():
+    class S(BaseState):
+        x: Field[int] = field(0)
+
+        @event
+        def s(self, value: int):
+            pass
+
+    # Handler doesn't have any _var_data because it's just a str
+    handler_var = Var.create(S.s)
+    assert handler_var._get_all_var_data() is None
+
+    # Ensure spec carries _var_data
+    spec_var = Var.create(S.s(S.x))
+    assert spec_var._get_all_var_data() == S.x._get_all_var_data()
+
+    # Needed to instantiate the EventChain
+    def _args_spec(value: Var[int]) -> tuple[Var[int]]:
+        return (value,)
+
+    # Ensure chain carries _var_data
+    chain_var = Var.create(EventChain(events=[S.s(S.x)], args_spec=_args_spec))
+    assert chain_var._get_all_var_data() == S.x._get_all_var_data()