[ENG-4165] Consider default and default_factory for state vars (#4510)

* [ENG-4165] Consider default and default_factory for state vars

When determining whether a state var should be marked as optional, check that
it is missing both default and default_factory and is not required.

Fix #4471

* add test for default factory with rx.foreach (#4515)

---------

Co-authored-by: benedikt-bartscher <31854409+benedikt-bartscher@users.noreply.github.com>

reflex/state.py

@@ -1097,6 +1097,7 @@ def _set_default_value(cls, prop: Var):
         if (
             not field.required
             and field.default is None
+            and field.default_factory is None
             and not types.is_optional(prop._var_type)
         ):
             # Ensure frontend uses null coalescing when accessing.

tests/units/components/core/test_foreach.py

@@ -1,8 +1,10 @@
 from typing import Dict, List, Set, Tuple, Union
 
+import pydantic.v1
 import pytest
 
 from reflex import el
+from reflex.base import Base
 from reflex.components.component import Component
 from reflex.components.core.foreach import (
     Foreach,
@@ -18,6 +20,12 @@
 from reflex.vars.sequence import ArrayVar
 
 
+class ForEachTag(Base):
+    """A tag for testing the ForEach component."""
+
+    name: str = ""
+
+
 class ForEachState(BaseState):
     """A state for testing the ForEach component."""
 
@@ -46,6 +54,8 @@ class ForEachState(BaseState):
     bad_annotation_list: list = [["red", "orange"], ["yellow", "blue"]]
     color_index_tuple: Tuple[int, str] = (0, "red")
 
+    default_factory_list: list[ForEachTag] = pydantic.v1.Field(default_factory=list)
+
 
 class ComponentStateTest(ComponentState):
     """A test component state."""
@@ -290,3 +300,11 @@ def test_foreach_component_state():
             ForEachState.colors_list,
             ComponentStateTest.create,
         )
+
+
+def test_foreach_default_factory():
+    """Test that the default factory is called."""
+    _ = Foreach.create(
+        ForEachState.default_factory_list,
+        lambda tag: text(tag.name),
+    )