initial port of the UI kit

go/wasmruntime/reconcile.go

@@ -111,6 +111,13 @@ func patch(parent js.Value, o, x *vdom.VNode) {
 	default:
 		x.Runtime = o.Runtime // adopt dom + listeners
 		dom := rt(x).dom
+		if !dom.Truthy() {
+			// o was a hydration hole (no adopted DOM node, e.g. a server/client
+			// markup mismatch). Recreate this node fresh instead of calling into an
+			// undefined DOM handle.
+			parent.Call("appendChild", createDOM(x))
+			return
+		}
 		if x.Tag == "" {
 			if x.Text != o.Text {
 				dom.Set("nodeValue", x.Text)