From 36768965337db739e75d7fbfb9e098db91b638f4 Mon Sep 17 00:00:00 2001
From: Andreas Ehrencrona <andreas.ehrencrona@velik.it>
Date: Tue, 8 Jun 2021 18:29:35 +0400
Subject: [PATCH 1/3] Improved hydration performance by less reordering of
 nodes

---
 src/runtime/internal/dom.ts | 48 +++++++++++++++++++++++++++++++++----
 1 file changed, 43 insertions(+), 5 deletions(-)

diff --git a/src/runtime/internal/dom.ts b/src/runtime/internal/dom.ts
index 40471c298058..7eed56916192 100644
--- a/src/runtime/internal/dom.ts
+++ b/src/runtime/internal/dom.ts
@@ -1,11 +1,48 @@
 import { has_prop } from './utils';
 
-export function append(target: Node, node: Node) {
-	target.appendChild(node);
-}
+interface ClaimedNode extends Node {
+  /** 
+   * When a node is claimed, we know all its children will be appended during mount.
+   * Keep track of which children have already been re-appended, so we do not reorder them multiple times.
+   */
+  appendAt?: number;
+}
+
+export function append(target: ClaimedNode, node: Node) {
+  if (target.appendAt == null) {
+    target.appendChild(node);
+  } else {
+    const appendAt = target.appendAt;
+    const childNodes = target.childNodes;
+    const nextNode = childNodes[appendAt];
+
+    if (nextNode != node) {
+      if (nextNode) {
+        target.insertBefore(node, nextNode);
+      } else {
+        target.appendChild(node);
+      }
+    }
+
+    target.appendAt = childNodes.length == appendAt + 1 ? undefined : appendAt + 1;
+  }
+}
+
+export function insert(target: ClaimedNode, node: Node, anchor?: Node) {
+	if ((target as ClaimedNode).appendAt == null) {
+		target.insertBefore(node, anchor || null);
+  } else if (anchor == null) {
+		append(target, node);
+	} else {
+    const appendAt = target.appendAt;
+    const anchorIndex = Array.prototype.indexOf.call(target.childNodes, anchor);
+
+		if (anchorIndex < appendAt) {
+			target.appendAt = target.childNodes.length == appendAt + 1 ? undefined : appendAt + 1;
+		}
 
-export function insert(target: Node, node: Node, anchor?: Node) {
-	target.insertBefore(node, anchor || null);
+    target.insertBefore(node, anchor || null);
+  }
 }
 
 export function detach(node: Node) {
@@ -168,6 +205,7 @@ export function claim_element(nodes, name, attributes, svg) {
 			for (let k = 0; k < remove.length; k++) {
 				node.removeAttribute(remove[k]);
 			}
+      (node as ClaimedNode).appendAt = 0;
 			return nodes.splice(i, 1)[0];
 		}
 	}

From be778960644f8a3b8f657311dac011379f929bec Mon Sep 17 00:00:00 2001
From: Andreas Ehrencrona <andreas.ehrencrona@velik.it>
Date: Wed, 9 Jun 2021 08:27:08 +0400
Subject: [PATCH 2/3] micro-optimization

---
 src/runtime/internal/dom.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/runtime/internal/dom.ts b/src/runtime/internal/dom.ts
index 7eed56916192..c6e2481d6dab 100644
--- a/src/runtime/internal/dom.ts
+++ b/src/runtime/internal/dom.ts
@@ -41,7 +41,7 @@ export function insert(target: ClaimedNode, node: Node, anchor?: Node) {
 			target.appendAt = target.childNodes.length == appendAt + 1 ? undefined : appendAt + 1;
 		}
 
-    target.insertBefore(node, anchor || null);
+    target.insertBefore(node, anchor);
   }
 }
 

From b1b604ac11899b78c8f02a1ee344387ab94c0918 Mon Sep 17 00:00:00 2001
From: Andreas Ehrencrona <andreas.ehrencrona@velik.it>
Date: Wed, 9 Jun 2021 08:51:25 +0400
Subject: [PATCH 3/3] unnecessary case

---
 src/runtime/internal/dom.ts | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/src/runtime/internal/dom.ts b/src/runtime/internal/dom.ts
index c6e2481d6dab..b607fe5c9142 100644
--- a/src/runtime/internal/dom.ts
+++ b/src/runtime/internal/dom.ts
@@ -17,11 +17,7 @@ export function append(target: ClaimedNode, node: Node) {
     const nextNode = childNodes[appendAt];
 
     if (nextNode != node) {
-      if (nextNode) {
-        target.insertBefore(node, nextNode);
-      } else {
-        target.appendChild(node);
-      }
+			target.insertBefore(node, nextNode);
     }
 
     target.appendAt = childNodes.length == appendAt + 1 ? undefined : appendAt + 1;