use unique object instead of index as default key

we can change this in a later pull request

src/idom/core/layout.py

@@ -450,6 +450,33 @@ async def get(self) -> AbstractComponent:
         return component
 
 
+def _process_child_type_and_key(
+    children: List[Any],
+) -> Iterator[Tuple[Any, int, Any]]:
+    for child in children:
+        if isinstance(child, dict):
+            child_type = _DICT_TYPE
+            key = child.get("key")
+        elif isinstance(child, AbstractComponent):
+            child_type = _COMPONENT_TYPE
+            key = getattr(child, "key", None)
+        else:
+            child = f"{child}"
+            child_type = _STRING_TYPE
+            key = None
+
+        if key is None:
+            key = object()
+
+        yield (child, child_type, key)
+
+
+# used in _process_child_type_and_key
+_DICT_TYPE = 1
+_COMPONENT_TYPE = 2
+_STRING_TYPE = 3
+
+
 class _ModelEventTarget(TypedDict):
     target: str
     preventDefault: bool  # noqa
@@ -475,30 +502,3 @@ class _ModelVdomRequired(TypedDict, total=True):
 
 class _ModelVdom(_ModelVdomRequired, _ModelVdomOptional):
     """A VDOM dictionary model specifically for use with a :class:`Layout`"""
-
-
-def _process_child_type_and_key(
-    raw_children: List[Any],
-) -> Iterator[Tuple[Any, int, Any]]:
-    for index, child in enumerate(raw_children):
-        if isinstance(child, dict):
-            child_type = _DICT_TYPE
-            key = child.get("key")
-        elif isinstance(child, AbstractComponent):
-            child_type = _COMPONENT_TYPE
-            key = getattr(child, "key", None)
-        else:
-            child = f"{child}"
-            child_type = _STRING_TYPE
-            key = None
-
-        if key is None:
-            key = index
-
-        yield (child, child_type, key)
-
-
-# used in _process_child_type_and_key
-_DICT_TYPE = 1
-_COMPONENT_TYPE = 2
-_STRING_TYPE = 3

tests/test_core/test_layout.py

@@ -181,14 +181,14 @@ async def test_components_are_garbage_collected():
     def Outer():
         component = idom.hooks.current_hook().component
         live_components.add(id(component))
-        finalize(component, live_components.remove, id(component))
+        finalize(component, live_components.discard, id(component))
         return Inner()
 
     @idom.component
     def Inner():
         component = idom.hooks.current_hook().component
         live_components.add(id(component))
-        finalize(component, live_components.remove, id(component))
+        finalize(component, live_components.discard, id(component))
         return idom.html.div()
 
     async with idom.Layout(Outer()) as layout: