mirror some changes from main

packages/svelte/src/internal/client/dom/task.js

@@ -1,7 +1,7 @@
 import { run_all } from '../../shared/utils.js';
 
 // Fallback for when requestIdleCallback is not available
-export const request_idle_callback =
+const request_idle_callback =
 	typeof requestIdleCallback === 'undefined'
 		? (/** @type {() => void} */ cb) => setTimeout(cb, 1)
 		: requestIdleCallback;
@@ -11,10 +11,12 @@ let is_idle_task_queued = false;
 
 /** @type {Array<() => void>} */
 let queued_boundary_microtasks = [];
+
 /** @type {Array<() => void>} */
 let queued_post_microtasks = [];
+
 /** @type {Array<() => void>} */
-let queued_idle_tasks = [];
+let idle_tasks = [];
 
 export function flush_boundary_micro_tasks() {
 	const tasks = queued_boundary_microtasks.slice();
@@ -28,13 +30,10 @@ export function flush_post_micro_tasks() {
 	run_all(tasks);
 }
 
-export function flush_idle_tasks() {
+export function run_idle_tasks() {
-	if (is_idle_task_queued) {
+	var tasks = idle_tasks;
-		is_idle_task_queued = false;
+	idle_tasks = [];
-		const tasks = queued_idle_tasks.slice();
+	run_all(tasks);
-		queued_idle_tasks = [];
-		run_all(tasks);
-	}
 }
 
 function flush_all_micro_tasks() {
@@ -71,9 +70,9 @@ export function queue_micro_task(fn) {
  * @param {() => void} fn
  */
 export function queue_idle_task(fn) {
-	if (!is_idle_task_queued) {
+	if (idle_tasks.length === 0) {
-		is_idle_task_queued = true;
+		request_idle_callback(run_idle_tasks);
-		request_idle_callback(flush_idle_tasks);
 	}
-	queued_idle_tasks.push(fn);
+
+	idle_tasks.push(fn);
 }

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

@@ -27,11 +27,7 @@ import {
 	REACTION_IS_UPDATING,
 	EFFECT_ASYNC
 } from './constants.js';
-import {
+import { flush_boundary_micro_tasks, flush_post_micro_tasks, run_idle_tasks } from './dom/task.js';
-	flush_idle_tasks,
-	flush_boundary_micro_tasks,
-	flush_post_micro_tasks
-} from './dom/task.js';
 import { internal_set } from './reactivity/sources.js';
 import {
 	destroy_derived_effects,
@@ -937,7 +933,7 @@ export function flush_sync(fn) {
 
 		flush_boundary_micro_tasks();
 		flush_post_micro_tasks();
-		flush_idle_tasks();
+		run_idle_tasks();
 		if (queued_root_effects.length > 0 || root_effects.length > 0) {
 			flush_sync();
 		}