From 07609a91e77b2b106859051acc14cf44ca580206 Mon Sep 17 00:00:00 2001
From: Jovi De Croock <decroockjovi@gmail.com>
Date: Fri, 4 Sep 2026 21:16:25 +0200
Subject: [PATCH] perf: diff single-child render results without a wrapper
 array

diff() and diffElementNodes() wrapped every non-array render result in a
fresh [result] array before calling diffChildren(). The #2618 statistics
put exactly-one-child at 84% of all children diffs, so that is one
throwaway allocation per component and per element on nearly every
update. diffChildren now accepts the bare value and
constructNewChildrenArray reads it directly.

Core -6 B gz / -5 B br. Local paired bench (playwright, interleaved):
text-update -3..-6% warm, hydrate1k -3.5% cold, create/replace within noise.
---
 src/diff/children.js | 4 ++--
 src/diff/index.js    | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/diff/children.js b/src/diff/children.js
index ddf901a298..562f6f8f30 100644
--- a/src/diff/children.js
+++ b/src/diff/children.js
@@ -71,7 +71,7 @@ export function diffChildren(
 	/** @type {VNode[]} */
 	let oldChildren = oldParentVNode._children || EMPTY_ARR;
 
-	let newChildrenLength = renderResult.length;
+	let newChildrenLength = isArray(renderResult) ? renderResult.length : 1;
 
 	oldDom = constructNewChildrenArray(
 		newParentVNode,
@@ -184,7 +184,7 @@ function constructNewChildrenArray(
 	for (i = 0; i < newChildrenLength; i++) {
 		// @ts-expect-error We are reusing the childVNode variable to hold both the
 		// pre and post normalized childVNode
-		childVNode = renderResult[i];
+		childVNode = isArray(renderResult) ? renderResult[i] : renderResult;
 
 		if (
 			childVNode == NULL ||
diff --git a/src/diff/index.js b/src/diff/index.js
index 951dfb998d..e0b36aba37 100644
--- a/src/diff/index.js
+++ b/src/diff/index.js
@@ -334,7 +334,7 @@ export function diff(
 
 			oldDom = diffChildren(
 				parentDom,
-				isArray(renderResult) ? renderResult : [renderResult],
+				renderResult,
 				newVNode,
 				oldVNode,
 				globalContext,
@@ -677,7 +677,7 @@ function diffElementNodes(
 
 			diffChildren(
 				parentDom,
-				isArray(newChildren) ? newChildren : [newChildren],
+				newChildren,
 				newVNode,
 				oldVNode,
 				globalContext,