Fix mount use after removal/Simplify mounts a bit (#2834)

* remove clone mounted; mounted nodes should never leak into components?

* Remove the mount from vnodes after unmounting them

* Fix use after removal in iterator diffing

* remove logs

* Re-fix keyed list diffing

* Use new.len for diffing keyed lens and remove redundant check

* simplify core list diffing logic a bit

* remove println

* add proper asserts for new tests

---------

Co-authored-by: Jonathan Kelley <jkelleyrtp@gmail.com>

packages/core/src/any_props.rs

@@ -1,4 +1,4 @@
-use crate::{innerlude::CapturedPanic, nodes::RenderReturn, ComponentFunction};
+use crate::{innerlude::CapturedPanic, ComponentFunction, Element};
 use std::{any::Any, panic::AssertUnwindSafe};
 
 pub(crate) type BoxedAnyProps = Box<dyn AnyProps>;
@@ -6,7 +6,7 @@ pub(crate) type BoxedAnyProps = Box<dyn AnyProps>;
 /// A trait for a component that can be rendered.
 pub(crate) trait AnyProps: 'static {
     /// Render the component with the internal props.
-    fn render(&self) -> RenderReturn;
+    fn render(&self) -> Element;
     /// Make the old props equal to the new type erased props. Return if the props were equal and should be memoized.
     fn memoize(&mut self, other: &dyn Any) -> bool;
     /// Get the props as a type erased `dyn Any`.
@@ -74,20 +74,18 @@ impl<F: ComponentFunction<P, M> + Clone, P: Clone + 'static, M: 'static> AnyProp
         &mut self.props
     }
 
-    fn render(&self) -> RenderReturn {
+    fn render(&self) -> Element {
         let res = std::panic::catch_unwind(AssertUnwindSafe(move || {
             self.render_fn.rebuild(self.props.clone())
         }));
 
         match res {
-            Ok(node) => RenderReturn { node },
+            Ok(node) => node,
             Err(err) => {
                 let component_name = self.name;
                 tracing::error!("Panic while rendering component `{component_name}`: {err:?}");
                 let panic = CapturedPanic { error: err };
-                RenderReturn {
-                    node: Err(panic.into()),
-                }
+                Element::Err(panic.into())
             }
         }
     }

packages/core/src/diff/component.rs

@@ -9,11 +9,11 @@ use crate::{
         ElementRef, MountId, ScopeOrder, SuspenseBoundaryProps, SuspenseBoundaryPropsWithOwner,
         VComponent, WriteMutations,
     },
-    nodes::VNode,
+    nodes::{AsVNode, VNode},
     prelude::SuspenseContext,
     scopes::ScopeId,
     virtual_dom::VirtualDom,
-    RenderReturn,
+    Element,
 };
 
 impl VirtualDom {
@@ -36,11 +36,11 @@ impl VirtualDom {
         &mut self,
         to: Option<&mut M>,
         scope: ScopeId,
-        new_nodes: RenderReturn,
+        new_nodes: Element,
     ) {
         self.runtime.clone().with_scope_on_stack(scope, || {
             // We don't diff the nodes if the scope is suspended or has an error
-            let Ok(new_real_nodes) = &new_nodes.node else {
+            let Ok(new_real_nodes) = &new_nodes else {
                 return;
             };
             let scope_state = &mut self.scopes[scope.0];
@@ -51,7 +51,8 @@ impl VirtualDom {
             // If it is suspended, we need to diff it but write the mutations nothing
             // Note: It is important that we still diff the scope even if it is suspended, because the scope may render other child components which may change between renders
             let mut render_to = to.filter(|_| self.runtime.scope_should_render(scope));
-            old.diff_node(new_real_nodes, self, render_to.as_deref_mut());
+            old.as_vnode()
+                .diff_node(new_real_nodes, self, render_to.as_deref_mut());
 
             self.scopes[scope.0].last_rendered_node = Some(new_nodes);
 
@@ -69,7 +70,7 @@ impl VirtualDom {
         &mut self,
         to: Option<&mut M>,
         scope: ScopeId,
-        new_nodes: RenderReturn,
+        new_nodes: Element,
         parent: Option<ElementRef>,
     ) -> usize {
         self.runtime.clone().with_scope_on_stack(scope, || {
@@ -79,7 +80,9 @@ impl VirtualDom {
             let mut render_to = to.filter(|_| self.runtime.scope_should_render(scope));
 
             // Create the node
-            let nodes = new_nodes.create(self, parent, render_to.as_deref_mut());
+            let nodes = new_nodes
+                .as_vnode()
+                .create(self, parent, render_to.as_deref_mut());
 
             // Then set the new node as the last rendered node
             self.scopes[scope.0].last_rendered_node = Some(new_nodes);
@@ -104,8 +107,12 @@ impl VirtualDom {
 
         // Remove the component from the dom
         if let Some(node) = self.scopes[scope_id.0].last_rendered_node.as_ref() {
-            node.clone_mounted()
-                .remove_node_inner(self, to, destroy_component_state, replace_with)
+            node.clone().as_vnode().remove_node_inner(
+                self,
+                to,
+                destroy_component_state,
+                replace_with,
+            )
         };
 
         if destroy_component_state {

packages/core/src/diff/iterator.rs

@@ -133,29 +133,17 @@ impl VirtualDom {
         let new_middle = &new[left_offset..(new.len() - right_offset)];
 
         debug_assert!(
-            !((old_middle.len() == new_middle.len()) && old_middle.is_empty()),
-            "keyed children must have the same number of children"
+            !old_middle.is_empty(),
+            "Old middle returned from `diff_keyed_ends` should not be empty"
+        );
+        debug_assert!(
+            !new_middle.is_empty(),
+            "New middle returned from `diff_keyed_ends` should not be empty"
         );
 
+        // A few nodes in the middle were removed, just remove the old nodes
         if new_middle.is_empty() {
-            // remove the old elements
             self.remove_nodes(to, old_middle, None);
-        } else if old_middle.is_empty() {
-            // there were no old elements, so just create the new elements
-            // we need to find the right "foothold" though - we shouldn't use the "append" at all
-            if left_offset == 0 {
-                // insert at the beginning of the old list
-                let foothold = &old[old.len() - right_offset];
-                self.create_and_insert_before(to, new_middle, foothold, parent);
-            } else if right_offset == 0 {
-                // insert at the end  the old list
-                let foothold = old.last().unwrap();
-                self.create_and_insert_after(to, new_middle, foothold, parent);
-            } else {
-                // inserting in the middle
-                let foothold = &old[left_offset - 1];
-                self.create_and_insert_after(to, new_middle, foothold, parent);
-            }
         } else {
             self.diff_keyed_middle(to, old_middle, new_middle, parent);
         }
@@ -187,14 +175,7 @@ impl VirtualDom {
         // If that was all of the old children, then create and append the remaining
         // new children and we're finished.
         if left_offset == old.len() {
-            self.create_and_insert_after(to, &new[left_offset..], old.last().unwrap(), parent);
-            return None;
-        }
-
-        // And if that was all of the new children, then remove all of the remaining
-        // old children and we're finished.
-        if left_offset == new.len() {
-            self.remove_nodes(to, &old[left_offset..], None);
+            self.create_and_insert_after(to, &new[left_offset..], &new[left_offset - 1], parent);
             return None;
         }
 
@@ -209,6 +190,35 @@ impl VirtualDom {
             right_offset += 1;
         }
 
+        // If that was all of the old children, then create and prepend the remaining
+        // new children and we're finished.
+        if right_offset == old.len() {
+            self.create_and_insert_before(
+                to,
+                &new[..new.len() - right_offset],
+                &new[new.len() - right_offset],
+                parent,
+            );
+            return None;
+        }
+
+        // If the right offset + the left offset is the same as the new length, then we just need to remove the old nodes
+        if right_offset + left_offset == new.len() {
+            self.remove_nodes(to, &old[left_offset..old.len() - right_offset], None);
+            return None;
+        }
+
+        // If the right offset + the left offset is the same as the old length, then we just need to add the new nodes
+        if right_offset + left_offset == old.len() {
+            self.create_and_insert_before(
+                to,
+                &new[left_offset..new.len() - right_offset],
+                &new[new.len() - right_offset],
+                parent,
+            );
+            return None;
+        }
+
         Some((left_offset, right_offset))
     }
 

packages/core/src/diff/node.rs

@@ -35,8 +35,6 @@ impl VNode {
             return self.replace(std::slice::from_ref(new), parent, dom, to);
         }
 
-        let mount_id = self.mount.get();
-
         self.move_mount_to(new, dom);
 
         // If the templates are the same, we don't need to do anything, except copy over the mount information
@@ -52,6 +50,7 @@ impl VNode {
         }
 
         // Now diff the dynamic nodes
+        let mount_id = new.mount.get();
         for (dyn_node_idx, (old, new)) in self
             .dynamic_nodes
             .iter()
@@ -64,7 +63,7 @@ impl VNode {
 
     fn move_mount_to(&self, new: &VNode, dom: &mut VirtualDom) {
         // Copy over the mount information
-        let mount_id = self.mount.get();
+        let mount_id = self.mount.take();
         new.mount.set(mount_id);
 
         if mount_id.mounted() {
@@ -72,7 +71,7 @@ impl VNode {
             let mount = &mut mounts[mount_id.0];
 
             // Update the reference to the node for bubbling events
-            mount.node = new.clone_mounted();
+            mount.node = new.clone();
         }
     }
 
@@ -293,6 +292,7 @@ impl VNode {
         self.reclaim_roots(mount, dom, to, destroy_component_state, replace_with);
 
         if destroy_component_state {
+            let mount = self.mount.take();
             // Remove the mount information
             dom.runtime.mounts.borrow_mut().remove(mount.0);
         }
@@ -416,7 +416,7 @@ impl VNode {
         dom: &mut VirtualDom,
         to: &mut impl WriteMutations,
     ) {
-        let mount_id = self.mount.get();
+        let mount_id = new.mount.get();
         for (idx, (old_attrs, new_attrs)) in self
             .dynamic_attrs
             .iter()
@@ -535,7 +535,7 @@ impl VNode {
             self.mount.set(mount);
             tracing::trace!(?self, ?mount, "creating template");
             entry.insert(VNodeMount {
-                node: self.clone_mounted(),
+                node: self.clone(),
                 parent,
                 root_ids: vec![ElementId(0); template.roots.len()].into_boxed_slice(),
                 mounted_attributes: vec![ElementId(0); template.attr_paths.len()]
@@ -559,7 +559,8 @@ impl VNode {
                     .as_usize()
                     .expect("node should already be mounted"),
             ),
-            "Node mount should be valid"
+            "Tried to find mount {:?} in dom.mounts, but it wasn't there",
+            self.mount.get()
         );
         let mount = self.mount.get();
 

packages/core/src/error_boundary.rs

@@ -451,17 +451,6 @@ impl CapturedError {
         self
     }
 
-    /// Clone the error while retaining the mounted information of the error
-    pub(crate) fn clone_mounted(&self) -> Self {
-        Self {
-            error: self.error.clone(),
-            backtrace: self.backtrace.clone(),
-            scope: self.scope,
-            render: self.render.clone_mounted(),
-            context: self.context.clone(),
-        }
-    }
-
     /// Get a VNode representation of the error if the error provides one
     pub fn show(&self) -> Option<Element> {
         if self.render == VNode::placeholder() {

packages/core/src/lib.rs

@@ -76,9 +76,9 @@ pub use crate::innerlude::{
     fc_to_builder, generation, schedule_update, schedule_update_any, use_hook, vdom_is_rendering,
     AnyValue, Attribute, AttributeValue, CapturedError, Component, ComponentFunction, DynamicNode,
     Element, ElementId, Event, Fragment, HasAttributes, IntoDynNode, MarkerWrapper, Mutation,
-    Mutations, NoOpMutations, Ok, Properties, RenderReturn, Result, Runtime, ScopeId, ScopeState,
-    SpawnIfAsync, Task, Template, TemplateAttribute, TemplateNode, VComponent, VNode, VNodeInner,
-    VPlaceholder, VText, VirtualDom, WriteMutations,
+    Mutations, NoOpMutations, Ok, Properties, Result, Runtime, ScopeId, ScopeState, SpawnIfAsync,
+    Task, Template, TemplateAttribute, TemplateNode, VComponent, VNode, VNodeInner, VPlaceholder,
+    VText, VirtualDom, WriteMutations,
 };
 
 /// The purpose of this module is to alleviate imports of many common types
@@ -94,8 +94,8 @@ pub mod prelude {
         use_hook_with_cleanup, with_owner, AnyValue, Attribute, Callback, Component,
         ComponentFunction, Context, Element, ErrorBoundary, ErrorContext, Event, EventHandler,
         Fragment, HasAttributes, IntoAttributeValue, IntoDynNode, OptionStringFromMarker,
-        Properties, ReactiveContext, RenderError, RenderReturn, Runtime, RuntimeGuard, ScopeId,
-        ScopeState, SuperFrom, SuperInto, SuspendedFuture, SuspenseBoundary, SuspenseBoundaryProps,
+        Properties, ReactiveContext, RenderError, Runtime, RuntimeGuard, ScopeId, ScopeState,
+        SuperFrom, SuperInto, SuspendedFuture, SuspenseBoundary, SuspenseBoundaryProps,
         SuspenseContext, SuspenseExtension, Task, Template, TemplateAttribute, TemplateNode, VNode,
         VNodeInner, VirtualDom,
     };

packages/core/src/nodes.rs

@@ -1,4 +1,5 @@
-use crate::innerlude::{RenderError, VProps};
+use crate::innerlude::VProps;
+use crate::prelude::RenderError;
 use crate::{any_props::BoxedAnyProps, innerlude::ScopeState};
 use crate::{arena::ElementId, Element, Event};
 use crate::{
@@ -6,7 +7,7 @@ use crate::{
     properties::ComponentFunction,
 };
 use crate::{Properties, ScopeId, VirtualDom};
-use std::ops::{Deref, DerefMut};
+use std::ops::Deref;
 use std::rc::Rc;
 use std::vec;
 use std::{
@@ -15,77 +16,6 @@ use std::{
     fmt::{Arguments, Debug},
 };
 
-/// The actual state of the component's most recent computation
-///
-/// If the component returned early (e.g. `return None`), this will be Aborted(None)
-#[derive(Debug)]
-pub struct RenderReturn {
-    /// The node that was rendered
-    pub(crate) node: Element,
-}
-
-impl From<RenderReturn> for VNode {
-    fn from(val: RenderReturn) -> Self {
-        match val.node {
-            Ok(node) => node,
-            Err(RenderError::Aborted(e)) => e.render,
-            Err(RenderError::Suspended(fut)) => fut.placeholder,
-        }
-    }
-}
-
-impl From<Element> for RenderReturn {
-    fn from(node: Element) -> Self {
-        RenderReturn { node }
-    }
-}
-
-impl Clone for RenderReturn {
-    fn clone(&self) -> Self {
-        match &self.node {
-            Ok(node) => RenderReturn {
-                node: Ok(node.clone_mounted()),
-            },
-            Err(RenderError::Aborted(err)) => RenderReturn {
-                node: Err(RenderError::Aborted(err.clone_mounted())),
-            },
-            Err(RenderError::Suspended(fut)) => RenderReturn {
-                node: Err(RenderError::Suspended(fut.clone_mounted())),
-            },
-        }
-    }
-}
-
-impl Default for RenderReturn {
-    fn default() -> Self {
-        RenderReturn {
-            node: Ok(VNode::placeholder()),
-        }
-    }
-}
-
-impl Deref for RenderReturn {
-    type Target = VNode;
-
-    fn deref(&self) -> &Self::Target {
-        match &self.node {
-            Ok(node) => node,
-            Err(RenderError::Aborted(err)) => &err.render,
-            Err(RenderError::Suspended(fut)) => &fut.placeholder,
-        }
-    }
-}
-
-impl DerefMut for RenderReturn {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        match &mut self.node {
-            Ok(node) => node,
-            Err(RenderError::Aborted(err)) => &mut err.render,
-            Err(RenderError::Suspended(fut)) => &mut fut.placeholder,
-        }
-    }
-}
-
 /// The information about the
 #[derive(Debug)]
 pub(crate) struct VNodeMount {
@@ -162,7 +92,7 @@ pub struct VNodeInner {
 ///
 /// The dynamic parts of the template are stored separately from the static parts. This allows faster diffing by skipping
 /// static parts of the template.
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct VNode {
     vnode: Rc<VNodeInner>,
 
@@ -170,15 +100,44 @@ pub struct VNode {
     pub(crate) mount: Cell<MountId>,
 }
 
-impl Clone for VNode {
-    fn clone(&self) -> Self {
-        Self {
-            vnode: self.vnode.clone(),
-            mount: Default::default(),
+impl AsRef<VNode> for Element {
+    fn as_ref(&self) -> &VNode {
+        match self {
+            Element::Ok(node) => node,
+            Element::Err(RenderError::Aborted(err)) => &err.render,
+            Element::Err(RenderError::Suspended(fut)) => &fut.placeholder,
+        }
+    }
+}
+
+impl From<&Element> for VNode {
+    fn from(val: &Element) -> Self {
+        AsRef::as_ref(val).clone()
+    }
+}
+
+impl From<Element> for VNode {
+    fn from(val: Element) -> Self {
+        match val {
+            Element::Ok(node) => node,
+            Element::Err(RenderError::Aborted(err)) => err.render,
+            Element::Err(RenderError::Suspended(fut)) => fut.placeholder,
         }
     }
 }
 
+/// A tiny helper trait to get the vnode for a Element
+pub(crate) trait AsVNode {
+    /// Get the vnode for this element
+    fn as_vnode(&self) -> &VNode;
+}
+
+impl AsVNode for Element {
+    fn as_vnode(&self) -> &VNode {
+        AsRef::as_ref(self)
+    }
+}
+
 impl Default for VNode {
     fn default() -> Self {
         Self::placeholder()
@@ -223,14 +182,6 @@ impl Deref for VNode {
 }
 
 impl VNode {
-    /// Clone the element while retaining the mount information of the node
-    pub(crate) fn clone_mounted(&self) -> Self {
-        Self {
-            vnode: self.vnode.clone(),
-            mount: self.mount.clone(),
-        }
-    }
-
     /// Create a template with no nodes that will be skipped over during diffing
     pub fn empty() -> Element {
         Ok(Self::default())

packages/core/src/scope_arena.rs

@@ -1,4 +1,4 @@
-use crate::innerlude::{throw_error, RenderError, RenderReturn, ScopeOrder};
+use crate::innerlude::{throw_error, RenderError, ScopeOrder};
 use crate::prelude::ReactiveContext;
 use crate::scope_context::SuspenseLocation;
 use crate::{
@@ -48,7 +48,7 @@ impl VirtualDom {
     /// Run a scope and return the rendered nodes. This will not modify the DOM or update the last rendered node of the scope.
     #[tracing::instrument(skip(self), level = "trace", name = "VirtualDom::run_scope")]
     #[track_caller]
-    pub(crate) fn run_scope(&mut self, scope_id: ScopeId) -> RenderReturn {
+    pub(crate) fn run_scope(&mut self, scope_id: ScopeId) -> Element {
         // Ensure we are currently inside a `Runtime`.
         crate::Runtime::current().unwrap_or_else(|e| panic!("{}", e));
 
@@ -70,11 +70,7 @@ impl VirtualDom {
                 span.in_scope(|| {
                     scope.reactive_context.reset_and_run_in(|| {
                         let mut render_return = props.render();
-                        self.handle_element_return(
-                            &mut render_return.node,
-                            scope_id,
-                            &scope.state(),
-                        );
+                        self.handle_element_return(&mut render_return, scope_id, &scope.state());
                         render_return
                     })
                 })
@@ -102,7 +98,7 @@ impl VirtualDom {
                     "Error while rendering component `{}`:\n{e}",
                     scope_state.name
                 );
-                throw_error(e.clone_mounted());
+                throw_error(e.clone());
                 e.render = VNode::placeholder();
             }
             Err(RenderError::Suspended(e)) => {

packages/core/src/scopes.rs

@@ -1,6 +1,6 @@
 use crate::{
-    any_props::BoxedAnyProps, nodes::RenderReturn, reactive_context::ReactiveContext,
-    scope_context::Scope, Runtime, VNode,
+    any_props::BoxedAnyProps, nodes::AsVNode, reactive_context::ReactiveContext,
+    scope_context::Scope, Element, Runtime, VNode,
 };
 use std::{cell::Ref, rc::Rc};
 
@@ -70,7 +70,7 @@ pub struct ScopeState {
     pub(crate) context_id: ScopeId,
     /// The last node that has been rendered for this component. This node may not ben mounted
     /// During suspense, this component can be rendered in the background multiple times
-    pub(crate) last_rendered_node: Option<RenderReturn>,
+    pub(crate) last_rendered_node: Option<Element>,
     pub(crate) props: BoxedAnyProps,
     pub(crate) reactive_context: ReactiveContext,
 }
@@ -98,7 +98,7 @@ impl ScopeState {
     ///
     /// Returns [`None`] if the tree has not been built yet.
     pub fn try_root_node(&self) -> Option<&VNode> {
-        self.last_rendered_node.as_deref()
+        self.last_rendered_node.as_ref().map(AsVNode::as_vnode)
     }
 
     /// Returns the scope id of this [`ScopeState`].

packages/core/src/suspense/component.rs

@@ -306,23 +306,17 @@ impl SuspenseBoundaryProps {
                 SuspenseContext::downcast_suspense_boundary_from_scope(&dom.runtime, scope_id)
                     .unwrap();
 
-            let children = RenderReturn {
-                node: props
-                    .children
-                    .as_ref()
-                    .map(|node| node.clone_mounted())
-                    .map_err(Clone::clone),
-            };
+            let children = props.children.clone();
 
             // First always render the children in the background. Rendering the children may cause this boundary to suspend
             suspense_context.under_suspense_boundary(&dom.runtime(), || {
-                children.create(dom, parent, None::<&mut M>);
+                children.as_vnode().create(dom, parent, None::<&mut M>);
             });
 
             // Store the (now mounted) children back into the scope state
             let scope_state = &mut dom.scopes[scope_id.0];
             let props = Self::downcast_from_props(&mut *scope_state.props).unwrap();
-            props.children = children.clone().node;
+            props.children = children.clone();
 
             let scope_state = &mut dom.scopes[scope_id.0];
             let suspense_context = scope_state
@@ -345,11 +339,8 @@ impl SuspenseBoundaryProps {
                             .unwrap();
                         suspense_context.set_suspended_nodes(children.into());
                         let suspense_placeholder = props.fallback.call(suspense_context);
-                        let node = RenderReturn {
-                            node: suspense_placeholder,
-                        };
-                        let nodes_created = node.create(dom, parent, to);
-                        (node, nodes_created)
+                        let nodes_created = suspense_placeholder.as_vnode().create(dom, parent, to);
+                        (suspense_placeholder, nodes_created)
                     });
 
                 let scope_state = &mut dom.scopes[scope_id.0];
@@ -358,9 +349,11 @@ impl SuspenseBoundaryProps {
                 nodes_created
             } else {
                 // Otherwise just render the children in the real dom
-                debug_assert!(children.mount.get().mounted());
+                debug_assert!(children.as_vnode().mount.get().mounted());
                 let nodes_created = suspense_context
-                    .under_suspense_boundary(&dom.runtime(), || children.create(dom, parent, to));
+                    .under_suspense_boundary(&dom.runtime(), || {
+                        children.as_vnode().create(dom, parent, to)
+                    });
                 let scope_state = &mut dom.scopes[scope_id.0];
                 scope_state.last_rendered_node = Some(children);
                 let suspense_context =
@@ -403,7 +396,7 @@ impl SuspenseBoundaryProps {
 
             // Get the parent of the suspense boundary to later create children with the right parent
             let currently_rendered = scope_state.last_rendered_node.as_ref().unwrap().clone();
-            let mount = currently_rendered.mount.get();
+            let mount = currently_rendered.as_vnode().mount.get();
             let parent = {
                 let mounts = dom.runtime.mounts.borrow();
                 mounts
@@ -415,11 +408,7 @@ impl SuspenseBoundaryProps {
             let props = Self::downcast_from_props(&mut *scope_state.props).unwrap();
 
             // Unmount any children to reset any scopes under this suspense boundary
-            let children = props
-                .children
-                .as_ref()
-                .map(|node| node.clone_mounted())
-                .map_err(Clone::clone);
+            let children = props.children.clone();
             let suspense_context =
                 SuspenseContext::downcast_suspense_boundary_from_scope(&dom.runtime, scope_id)
                     .unwrap();
@@ -429,23 +418,24 @@ impl SuspenseBoundaryProps {
                 node.remove_node(&mut *dom, None::<&mut M>, None);
             }
             // Replace the rendered nodes with resolved nodes
-            currently_rendered.remove_node(&mut *dom, Some(to), Some(replace_with));
+            currently_rendered
+                .as_vnode()
+                .remove_node(&mut *dom, Some(to), Some(replace_with));
 
             // Switch to only writing templates
             only_write_templates(to);
 
-            let children = RenderReturn { node: children };
-            children.mount.take();
+            children.as_vnode().mount.take();
 
             // First always render the children in the background. Rendering the children may cause this boundary to suspend
             suspense_context.under_suspense_boundary(&dom.runtime(), || {
-                children.create(dom, parent, Some(to));
+                children.as_vnode().create(dom, parent, Some(to));
             });
 
             // Store the (now mounted) children back into the scope state
             let scope_state = &mut dom.scopes[scope_id.0];
             let props = Self::downcast_from_props(&mut *scope_state.props).unwrap();
-            props.children = children.clone().node;
+            props.children = children.clone();
             scope_state.last_rendered_node = Some(children);
         })
     }
@@ -461,7 +451,7 @@ impl SuspenseBoundaryProps {
                 .unwrap()
                 .clone();
 
-            let last_rendered_node = scope.last_rendered_node.as_ref().unwrap().clone_mounted();
+            let last_rendered_node = scope.last_rendered_node.as_ref().unwrap().clone();
 
             let Self {
                 fallback, children, ..
@@ -474,17 +464,19 @@ impl SuspenseBoundaryProps {
                 // We already have suspended nodes that still need to be suspended
                 // Just diff the normal and suspended nodes
                 (Some(suspended_nodes), true) => {
-                    let new_suspended_nodes: VNode = RenderReturn { node: children }.into();
+                    let new_suspended_nodes: VNode = children.into();
 
                     // Diff the placeholder nodes in the dom
                     let new_placeholder =
                         suspense_context.in_suspense_placeholder(&dom.runtime(), || {
                             let old_placeholder = last_rendered_node;
-                            let new_placeholder = RenderReturn {
-                                node: fallback.call(suspense_context.clone()),
-                            };
+                            let new_placeholder = fallback.call(suspense_context.clone());
 
-                            old_placeholder.diff_node(&new_placeholder, dom, to);
+                            old_placeholder.as_vnode().diff_node(
+                                new_placeholder.as_vnode(),
+                                dom,
+                                to,
+                            );
                             new_placeholder
                         });
 
@@ -506,10 +498,12 @@ impl SuspenseBoundaryProps {
                 // We have no suspended nodes, and we are not suspended. Just diff the children like normal
                 (None, false) => {
                     let old_children = last_rendered_node;
-                    let new_children = RenderReturn { node: children };
+                    let new_children = children;
 
                     suspense_context.under_suspense_boundary(&dom.runtime(), || {
-                        old_children.diff_node(&new_children, dom, to);
+                        old_children
+                            .as_vnode()
+                            .diff_node(new_children.as_vnode(), dom, to);
                     });
 
                     // Set the last rendered node to the new children
@@ -517,12 +511,10 @@ impl SuspenseBoundaryProps {
                 }
                 // We have no suspended nodes, but we just became suspended. Move the children to the background
                 (None, true) => {
-                    let old_children = last_rendered_node;
-                    let new_children: VNode = RenderReturn { node: children }.into();
+                    let old_children = last_rendered_node.as_vnode();
+                    let new_children: VNode = children.into();
 
-                    let new_placeholder = RenderReturn {
-                        node: fallback.call(suspense_context.clone()),
-                    };
+                    let new_placeholder = fallback.call(suspense_context.clone());
 
                     // Move the children to the background
                     let mount = old_children.mount.get();
@@ -530,7 +522,7 @@ impl SuspenseBoundaryProps {
 
                     suspense_context.in_suspense_placeholder(&dom.runtime(), || {
                         old_children.move_node_to_background(
-                            std::slice::from_ref(&*new_placeholder),
+                            std::slice::from_ref(new_placeholder.as_vnode()),
                             parent,
                             dom,
                             to,
@@ -559,17 +551,17 @@ impl SuspenseBoundaryProps {
                     // Take the suspended nodes out of the suspense boundary so the children know that the boundary is not suspended while diffing
                     let old_suspended_nodes = suspense_context.take_suspended_nodes().unwrap();
                     let old_placeholder = last_rendered_node;
-                    let new_children = RenderReturn { node: children };
+                    let new_children = children;
 
                     // First diff the two children nodes in the background
                     suspense_context.under_suspense_boundary(&dom.runtime(), || {
-                        old_suspended_nodes.diff_node(&new_children, dom, None::<&mut M>);
+                        old_suspended_nodes.diff_node(new_children.as_vnode(), dom, None::<&mut M>);
 
                         // Then replace the placeholder with the new children
-                        let mount = old_placeholder.mount.get();
+                        let mount = old_placeholder.as_vnode().mount.get();
                         let parent = dom.get_mounted_parent(mount);
-                        old_placeholder.replace(
-                            std::slice::from_ref(&*new_children),
+                        old_placeholder.as_vnode().replace(
+                            std::slice::from_ref(new_children.as_vnode()),
                             parent,
                             dom,
                             to,

packages/core/src/suspense/mod.rs

@@ -70,15 +70,6 @@ impl SuspendedFuture {
     pub fn task(&self) -> Task {
         self.task
     }
-
-    /// Clone the future while retaining the mounted information of the future
-    pub(crate) fn clone_mounted(&self) -> Self {
-        Self {
-            task: self.task,
-            origin: self.origin,
-            placeholder: self.placeholder.clone_mounted(),
-        }
-    }
 }
 
 /// A context with information about suspended components
@@ -117,7 +108,7 @@ impl SuspenseContext {
             .suspended_nodes
             .borrow()
             .as_ref()
-            .map(|node| node.clone_mounted())
+            .map(|node| node.clone())
     }
 
     /// Set the suspense boundary's suspended nodes

packages/core/tests/diff_dynamic_node.rs

@@ -47,3 +47,68 @@ fn toggle_option_text() {
         ]
     );
 }
+
+// Regression test for https://github.com/DioxusLabs/dioxus/issues/2815
+#[test]
+fn toggle_template() {
+    fn app() -> Element {
+        rsx!(
+            Comp {
+                if true {
+                    "{true}"
+                }
+            }
+        )
+    }
+
+    #[component]
+    fn Comp(children: Element) -> Element {
+        let show = generation() % 2 == 0;
+
+        rsx! {
+            if show {
+                {children}
+            }
+        }
+    }
+
+    let mut dom = VirtualDom::new(app);
+    dom.rebuild(&mut dioxus_core::NoOpMutations);
+
+    // Rendering again should replace the placeholder with an text node
+    dom.mark_dirty(ScopeId::APP);
+    assert_eq!(
+        dom.render_immediate_to_vec().edits,
+        [
+            CreatePlaceholder { id: ElementId(2) },
+            ReplaceWith { id: ElementId(1), m: 1 },
+        ]
+    );
+
+    dom.mark_dirty(ScopeId(ScopeId::APP.0 + 1));
+    assert_eq!(
+        dom.render_immediate_to_vec().edits,
+        [
+            CreateTextNode { value: "true".to_string(), id: ElementId(1) },
+            ReplaceWith { id: ElementId(2), m: 1 },
+        ]
+    );
+
+    dom.mark_dirty(ScopeId(ScopeId::APP.0 + 1));
+    assert_eq!(
+        dom.render_immediate_to_vec().edits,
+        [
+            CreatePlaceholder { id: ElementId(2) },
+            ReplaceWith { id: ElementId(1), m: 1 },
+        ]
+    );
+
+    dom.mark_dirty(ScopeId(ScopeId::APP.0 + 1));
+    assert_eq!(
+        dom.render_immediate_to_vec().edits,
+        [
+            CreateTextNode { value: "true".to_string(), id: ElementId(1) },
+            ReplaceWith { id: ElementId(2), m: 1 },
+        ]
+    );
+}

packages/core/tests/diff_keyed_list.rs

@@ -356,3 +356,92 @@ fn no_common_keys() {
         ]
     );
 }
+
+#[test]
+fn perfect_reverse() {
+    let mut dom = VirtualDom::new(|| {
+        let order: &[_] = match generation() % 2 {
+            0 => &[1, 2, 3, 4, 5, 6, 7, 8],
+            1 => &[9, 8, 7, 6, 5, 4, 3, 2, 1, 0],
+            _ => unreachable!(),
+        };
+
+        rsx!({ order.iter().map(|i| rsx!(div { key: "{i}" })) })
+    });
+
+    dom.rebuild(&mut dioxus_core::NoOpMutations);
+
+    dom.mark_dirty(ScopeId::APP);
+    let edits = dom.render_immediate_to_vec().edits;
+    assert_eq!(
+        edits,
+        [
+            LoadTemplate { index: 0, id: ElementId(9,) },
+            InsertAfter { id: ElementId(1,), m: 1 },
+            LoadTemplate { index: 0, id: ElementId(10,) },
+            PushRoot { id: ElementId(8,) },
+            PushRoot { id: ElementId(7,) },
+            PushRoot { id: ElementId(6,) },
+            PushRoot { id: ElementId(5,) },
+            PushRoot { id: ElementId(4,) },
+            PushRoot { id: ElementId(3,) },
+            PushRoot { id: ElementId(2,) },
+            InsertBefore { id: ElementId(1,), m: 8 },
+        ]
+    )
+}
+
+#[test]
+fn old_middle_empty_left_pivot() {
+    let mut dom = VirtualDom::new(|| {
+        let order: &[_] = match generation() % 2 {
+            0 => &[/* */ /* */ 6, 7, 8, 9, 10],
+            1 => &[/* */ 4, 5, /* */ 6, 7, 8, 9, 10],
+            _ => unreachable!(),
+        };
+
+        rsx!({ order.iter().map(|i| rsx!(div { key: "{i}" })) })
+    });
+
+    dom.rebuild(&mut dioxus_core::NoOpMutations);
+
+    dom.mark_dirty(ScopeId::APP);
+    let edits = dom.render_immediate_to_vec().edits;
+    assert_eq!(
+        edits,
+        [
+            LoadTemplate { index: 0, id: ElementId(6,) },
+            LoadTemplate { index: 0, id: ElementId(7,) },
+            InsertBefore { id: ElementId(1,), m: 2 },
+        ]
+    )
+}
+
+#[test]
+fn old_middle_empty_right_pivot() {
+    let mut dom = VirtualDom::new(|| {
+        let order: &[_] = match generation() % 2 {
+            0 => &[1, 2, 3, /*       */ 6, 7, 8, 9, 10],
+            1 => &[1, 2, 3, /* */ 4, 5, 6, 7, 8, 9, 10 /* */],
+
+            // 0 => &[/* */ 6, 7, 8, 9, 10],
+            // 1 => &[/* */ 6, 7, 8, 9, 10, /* */ 4, 5],
+            _ => unreachable!(),
+        };
+
+        rsx!({ order.iter().map(|i| rsx!(div { key: "{i}" })) })
+    });
+
+    dom.rebuild(&mut dioxus_core::NoOpMutations);
+
+    dom.mark_dirty(ScopeId::APP);
+    let edits = dom.render_immediate_to_vec().edits;
+    assert_eq!(
+        edits,
+        [
+            LoadTemplate { index: 0, id: ElementId(9) },
+            LoadTemplate { index: 0, id: ElementId(10) },
+            InsertBefore { id: ElementId(4), m: 2 },
+        ]
+    );
+}