fix: ensure child effects are removed from parent branches

.changeset/silly-lies-film.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: child effects are removed from parent branches

packages/svelte/src/internal/client/reactivity/deriveds.js

@@ -70,19 +70,22 @@ export function derived_safe_equal(fn) {
  * @returns {void}
  */
 function destroy_derived_children(signal) {
+	var effects = signal.effects;
+
 	// TODO: should it be possible to create effects in deriveds given they're meant to be pure?
-	if (signal.effects) {
-		for (var i = 0; i < signal.effects.length; i += 1) {
-			destroy_effect(signal.effects[i]);
-		}
+	if (effects !== null) {
 		signal.effects = null;
+		for (var i = 0; i < effects.length; i += 1) {
+			destroy_effect(effects[i]);
+		}
 	}
+	var deriveds = signal.deriveds;
 
-	if (signal.deriveds) {
-		for (i = 0; i < signal.deriveds.length; i += 1) {
-			destroy_derived(signal.deriveds[i]);
-		}
+	if (deriveds !== null) {
 		signal.deriveds = null;
+		for (i = 0; i < deriveds.length; i += 1) {
+			destroy_derived(deriveds[i]);
+		}
 	}
 }
 

packages/svelte/src/internal/client/reactivity/effects.js

@@ -237,11 +237,22 @@ export function destroy_effect(effect) {
 		remove(effect.dom);
 	}
 
+	var parent = effect.parent;
+
+	if (parent !== null && (effect.f & BRANCH_EFFECT) !== 0) {
+		var effects = parent.effects;
+		if (effects !== null) {
+			var index = effects.indexOf(effect);
+			effects.splice(index, 1);
+		}
+	}
+
 	effect.effects =
 		effect.teardown =
 		effect.ctx =
 		effect.dom =
 		effect.deps =
+		effect.parent =
 		// @ts-expect-error
 		effect.fn =
 			null;

packages/svelte/src/internal/client/runtime.js

@@ -353,11 +353,13 @@ export function remove_reactions(signal, start_index) {
  * @returns {void}
  */
 export function destroy_children(signal) {
-	if (signal.effects) {
-		for (var i = 0; i < signal.effects.length; i += 1) {
-			destroy_effect(signal.effects[i]);
-		}
+	var effects = signal.effects;
+
+	if (effects !== null) {
 		signal.effects = null;
+		for (var i = 0; i < effects.length; i += 1) {
+			destroy_effect(effects[i]);
+		}
 	}
 }