breaking: avoid flushing queued updates on mount/hydrat

Author: trueadm

.changeset/slow-gorillas-yawn.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+breaking: avoid flushing queued updates on mount/hydrate

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

@@ -79,8 +79,7 @@ export function set_text(text, value) {
  */
 export function mount(component, options) {
 	const anchor = options.anchor ?? options.target.appendChild(empty());
-	// Don't flush previous effects to ensure order of outer effects stays consistent
-	return flush_sync(() => _mount(component, { ...options, anchor }), false);
+	return _mount(component, { ...options, anchor });
 }
 
 /**

packages/svelte/tests/runtime-browser/samples/bind-playbackrate/_config.js

@@ -1,8 +1,10 @@
+import { flushSync } from 'svelte';
 import { test, ok } from '../../assert';
 
 export default test({
 	mode: ['client'],
 	async test({ assert, target }) {
+		flushSync();
 		const audio = target.querySelector('audio');
 		const button = target.querySelector('button');
 		ok(audio);

packages/svelte/tests/runtime-browser/samples/head-script/_config.js

@@ -1,7 +1,9 @@
+import { flushSync } from 'svelte';
 import { test } from '../../assert';
 
 export default test({
 	test({ assert, window }) {
+		flushSync();
 		document.dispatchEvent(new Event('DOMContentLoaded'));
 		assert.equal(window.document.querySelector('button')?.textContent, 'Hello world');
 	}

packages/svelte/tests/runtime-browser/samples/sole-script-tag/_config.js

@@ -1,10 +1,12 @@
+import { flushSync } from 'svelte';
 import { test } from '../../assert';
 
 export default test({
 	// Test that template with sole script tag does execute when instantiated in the client.
 	// Needs to be in this test suite because JSDOM does not quite get this right.
 	mode: ['client'],
 	test({ window, assert }) {
+		flushSync();
 		// In here to give effects etc time to execute
 		assert.htmlEqual(window.document.body.innerHTML, 'this should be executed');
 	}