From a7bc518f16d0501f2dc9169df8c56626a825f973 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Mon, 14 Apr 2025 11:28:13 -0400
Subject: [PATCH] WIP

---
 packages/svelte/src/internal/client/proxy.js     | 16 +++++++++++++++-
 .../src/internal/client/reactivity/sources.js    |  9 ---------
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/packages/svelte/src/internal/client/proxy.js b/packages/svelte/src/internal/client/proxy.js
index 6e82a9bd6b..3df5db751b 100644
--- a/packages/svelte/src/internal/client/proxy.js
+++ b/packages/svelte/src/internal/client/proxy.js
@@ -37,6 +37,8 @@ export function proxy(value, onchange) {
 	return create_proxy(value, onchange ? [onchange] : []);
 }
 
+let batching = false;
+
 /**
  * @template T
  * @param {T} value
@@ -165,6 +167,8 @@ export function create_proxy(value, onchanges) {
 
 			if (prop === PROXY_ONCHANGE_SYMBOL) {
 				return (/** @type {(Array<() => void>)} */ callbacks, /** @type {boolean} */ remove) => {
+					if (callbacks === onchanges) return;
+
 					if (remove) {
 						let i = callbacks.length;
 						while (i--) {
@@ -258,6 +262,10 @@ export function create_proxy(value, onchanges) {
 			var s = sources.get(prop);
 			var has = prop in target;
 
+			if (is_proxied_array && prop === 'length') {
+				batching = true;
+			}
+
 			// if we are changing the length of the array we batch all the changes
 			// to the sources and the original value by calling batch_onchange and immediately
 			// invoking it...otherwise we just invoke an identity function
@@ -312,7 +320,13 @@ export function create_proxy(value, onchanges) {
 				}
 			})();
 
-			run_all(onchanges);
+			if (is_proxied_array && prop === 'length') {
+				batching = false;
+			}
+
+			if (!batching) {
+				run_all(onchanges);
+			}
 
 			var descriptor = Reflect.getOwnPropertyDescriptor(target, prop);
 
diff --git a/packages/svelte/src/internal/client/reactivity/sources.js b/packages/svelte/src/internal/client/reactivity/sources.js
index 13eb445a0f..e1d3b61275 100644
--- a/packages/svelte/src/internal/client/reactivity/sources.js
+++ b/packages/svelte/src/internal/client/reactivity/sources.js
@@ -252,15 +252,6 @@ export function internal_set(source, value) {
 
 			inspect_effects.clear();
 		}
-
-		var onchange = source.o;
-		if (onchange) {
-			if (onchange_batch) {
-				onchange_batch.add(onchange);
-			} else {
-				onchange();
-			}
-		}
 	}
 
 	return value;