fix walk children

src/textual/app.py

@@ -2153,6 +2153,9 @@ class App(Generic[ReturnType], DOMNode):
             if widget.parent is not None:
                 widget.parent._nodes._remove(widget)
 
+        for node in pruned_remove:
+            node._detach()
+
         # Return the list of widgets that should end up being sent off in a
         # prune event.
         return pruned_remove

src/textual/reactive.py

@@ -239,9 +239,10 @@ class Reactive(Generic[ReactiveType]):
                     )
                 )
 
-        watch_function = getattr(obj, f"watch_{name}", None)
-        if callable(watch_function):
-            invoke_watcher(watch_function, old_value, value)
+        if obj.is_attached:
+            watch_function = getattr(obj, f"watch_{name}", None)
+            if callable(watch_function):
+                invoke_watcher(watch_function, old_value, value)
 
         # Process "global" watchers
         watchers: list[tuple[Reactable, Callable]]
@@ -342,7 +343,6 @@ def _watch(
         callback: A callable to call when the attribute changes.
         init: True to call watcher initialization. Defaults to True.
     """
-
     if not hasattr(obj, "__watchers"):
         setattr(obj, "__watchers", {})
     watchers: dict[str, list[tuple[Reactable, Callable]]] = getattr(obj, "__watchers")

src/textual/walk.py

@@ -53,7 +53,7 @@ def walk_depth_first(
     """
     from textual.dom import DOMNode
 
-    stack: list[Iterator[DOMNode]] = [iter(root._nodes)]
+    stack: list[Iterator[DOMNode]] = [iter(root.children)]
     pop = stack.pop
     push = stack.append
     check_type = filter_type or DOMNode