compare definition ID to see if changed in layout

Author: rmorshea

src/idom/core/component.py

@@ -51,6 +51,10 @@ def __init__(
         self._kwargs = kwargs
         self.key = key
 
+    @property
+    def definition_id(self) -> int:
+        return id(self._func)
+
     def render(self) -> VdomDict:
         model = self._func(*self._args, **self._kwargs)
         if isinstance(model, ComponentType):

src/idom/core/layout.py

@@ -511,6 +511,10 @@ def _update_component_model_state(
         life_cycle_state=(
             _update_life_cycle_state(old_model_state.life_cycle_state, new_component)
             if old_model_state.is_component_state
+            and (
+                old_model_state.life_cycle_state.component.definition_id
+                == new_component.definition_id
+            )
             else _make_life_cycle_state(new_component, schedule_render)
         ),
     )

src/idom/core/proto.py

@@ -32,6 +32,12 @@ class ComponentType(Protocol):
     key: Key | None
     """An identifier which is unique amongst a component's immediate siblings"""
 
+    definition_id: int
+    """A globally unique identifier for this component definition.
+
+    Usually the :func:`id` of this class or an underlying function.
+    """
+
     def render(self) -> VdomDict:
         """Render the component's :class:`VdomDict`."""