yew/vlist: optimize diffing and patching

packages/yew/src/html/component/scope.rs

@@ -170,7 +170,7 @@ impl<COMP: Component> Scope<COMP> {
     ) {
         let placeholder = {
             let placeholder: Node = document().create_text_node("").into();
-            insert_node(&placeholder, &parent, next_sibling.get());
+            insert_node(&placeholder, &parent, &next_sibling.get());
             node_ref.set(Some(placeholder.clone()));
             VNode::VRef(placeholder)
         };

packages/yew/src/html/mod.rs

@@ -64,7 +64,7 @@ pub type Html = VNode;
 /// ```
 /// ## Relevant examples
 /// - [Node Refs](https://github.com/yewstack/yew/tree/master/examples/node_refs)
-#[derive(Debug, Default, Clone)]
+#[derive(Default, Clone)]
 pub struct NodeRef(Rc<RefCell<NodeRefInner>>);
 
 impl PartialEq for NodeRef {
@@ -73,6 +73,16 @@ impl PartialEq for NodeRef {
     }
 }
 
+impl std::fmt::Debug for NodeRef {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "NodeRef {{ references: {:?} }}",
+            self.get().map(|n| crate::utils::print_node(&n))
+        )
+    }
+}
+
 #[derive(PartialEq, Debug, Default, Clone)]
 struct NodeRefInner {
     node: Option<Node>,

packages/yew/src/utils.rs

@@ -89,3 +89,13 @@ impl<IN, OUT> IntoIterator for NodeSeq<IN, OUT> {
         self.0.into_iter()
     }
 }
+
+/// Print Node contents as a string for debugging purposes
+pub fn print_node(n: &web_sys::Node) -> String {
+    use wasm_bindgen::JsCast;
+
+    match n.dyn_ref::<web_sys::Element>() {
+        Some(el) => el.outer_html(),
+        None => n.text_content().unwrap_or_default(),
+    }
+}

packages/yew/src/virtual_dom/mod.rs

@@ -353,10 +353,10 @@ pub(crate) trait VDiff {
     ) -> NodeRef;
 }
 
-pub(crate) fn insert_node(node: &Node, parent: &Element, next_sibling: Option<Node>) {
+pub(crate) fn insert_node(node: &Node, parent: &Element, next_sibling: &Option<Node>) {
     match next_sibling {
         Some(next_sibling) => parent
-            .insert_before(&node, Some(&next_sibling))
+            .insert_before(&node, Some(next_sibling))
             .expect("failed to insert tag before next sibling"),
         None => parent.append_child(node).expect("failed to append child"),
     };

packages/yew/src/virtual_dom/vcomp.rs

@@ -99,7 +99,6 @@ impl VComp {
         }
     }
 
-    #[allow(unused)]
     pub(crate) fn root_vnode(&self) -> Option<impl Deref<Target = VNode> + '_> {
         self.scope.as_ref().and_then(|scope| scope.root_vnode())
     }
@@ -250,7 +249,7 @@ impl PartialEq for VComp {
 
 impl fmt::Debug for VComp {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.write_str("VComp")
+        write!(f, "VComp {{ root: {:?} }}", self.root_vnode().as_deref())
     }
 }