From 09510c8c5c0888578446781e54f2229428e21bfc Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <trueadm@users.noreply.github.com>
Date: Tue, 21 Jan 2025 20:01:14 +0000
Subject: [PATCH] fix: address regression with untrack (#15079)

* fix: address regression with untrack

* add test
---
 .changeset/ninety-chefs-know.md               |  5 ++
 .../src/internal/client/reactivity/sources.js |  2 +-
 .../untracked-derived-local/_config.js        |  5 ++
 .../untracked-derived-local/main.svelte       | 47 +++++++++++++++++++
 4 files changed, 58 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/ninety-chefs-know.md
 create mode 100644 packages/svelte/tests/runtime-runes/samples/untracked-derived-local/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/untracked-derived-local/main.svelte

diff --git a/.changeset/ninety-chefs-know.md b/.changeset/ninety-chefs-know.md
new file mode 100644
index 0000000000..b5eac6a07a
--- /dev/null
+++ b/.changeset/ninety-chefs-know.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: address regression with untrack
diff --git a/packages/svelte/src/internal/client/reactivity/sources.js b/packages/svelte/src/internal/client/reactivity/sources.js
index d10008dae2..c2448c9ee5 100644
--- a/packages/svelte/src/internal/client/reactivity/sources.js
+++ b/packages/svelte/src/internal/client/reactivity/sources.js
@@ -116,7 +116,7 @@ export function mutable_state(v, immutable = false) {
  */
 /*#__NO_SIDE_EFFECTS__*/
 function push_derived_source(source) {
-	if (active_reaction !== null && (active_reaction.f & DERIVED) !== 0) {
+	if (active_reaction !== null && !untracking && (active_reaction.f & DERIVED) !== 0) {
 		if (derived_sources === null) {
 			set_derived_sources([source]);
 		} else {
diff --git a/packages/svelte/tests/runtime-runes/samples/untracked-derived-local/_config.js b/packages/svelte/tests/runtime-runes/samples/untracked-derived-local/_config.js
new file mode 100644
index 0000000000..1fe92ed2d7
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/untracked-derived-local/_config.js
@@ -0,0 +1,5 @@
+import { test } from '../../test';
+
+export default test({
+	html: `3`
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/untracked-derived-local/main.svelte b/packages/svelte/tests/runtime-runes/samples/untracked-derived-local/main.svelte
new file mode 100644
index 0000000000..0873eb741d
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/untracked-derived-local/main.svelte
@@ -0,0 +1,47 @@
+<script module>
+	import { untrack } from 'svelte'
+	import { SvelteMap } from 'svelte/reactivity'
+
+	class Foo {
+		id
+		updateTime = $state(Date.now())
+
+		constructor(id) {
+			this.id = id
+		}
+	}
+
+	class Store {
+		cache = new SvelteMap()
+		ids = $state([1, 2, 3])
+
+		getOrDefault(id) {
+			let ret = this.cache.get(id)
+
+			if (ret) {
+				return ret
+			}
+
+			ret = untrack(() => {
+				ret = new Foo(id)
+				this.cache.set(id, ret)
+				return ret
+			})
+			this.cache.get(id)
+
+			return ret
+		}
+
+		get values() {
+			return this.ids.map(id => this.getOrDefault(id)).sort((a, b) => b.updateTime - a.updateTime)
+		}
+	}
+
+	const store = new Store()
+</script>
+
+<script>
+	const test = $derived.by(() => store.values.length)
+</script>
+
+{test}