fix: prevent component pre-mounting in async boundaries

packages/svelte/src/internal/client/dom/blocks/svelte-component.js

@@ -4,7 +4,7 @@ import { EFFECT_TRANSPARENT } from '#client/constants';
 import { block, branch, pause_effect } from '../../reactivity/effects.js';
 import { current_batch } from '../../reactivity/batch.js';
 import { hydrate_next, hydrate_node, hydrating } from '../hydration.js';
-import { create_text, should_defer_append } from '../operations.js';
+import { should_defer_append } from '../operations.js';
 
 /**
  * @template P
@@ -27,19 +27,13 @@ export function component(node, get_component, render_fn) {
 	/** @type {Effect | null} */
 	var effect;
 
-	/** @type {DocumentFragment | null} */
-	var offscreen_fragment = null;
-
 	/** @type {Effect | null} */
 	var pending_effect = null;
 
 	function commit() {
-		if (offscreen_fragment) {
+		if (effect) {
-			// remove the anchor
+			pause_effect(effect);
-			/** @type {Text} */ (offscreen_fragment.lastChild).remove();
+			effect = null;
-
-			anchor.before(offscreen_fragment);
-			offscreen_fragment = null;
 		}
 
 		effect = pending_effect;
@@ -51,25 +45,23 @@ export function component(node, get_component, render_fn) {
 
 		var defer = should_defer_append();
 
-		if (effect) {
-			pause_effect(effect);
-			effect = null;
-		}
-
 		if (component) {
-			var target = anchor;
-
 			if (defer) {
-				offscreen_fragment = document.createDocumentFragment();
-				offscreen_fragment.append((target = create_text()));
 				if (effect) {
 					/** @type {Batch} */ (current_batch).skipped_effects.add(effect);
 				}
+				/** @type {Batch} */ (current_batch).add_callback(() => {
+					if (effect) {
+						pause_effect(effect);
+						effect = null;
 					}
-			pending_effect = branch(() => render_fn(target, component));
+					effect = branch(() => render_fn(anchor, component));
+				});
+			} else {
+				pending_effect = branch(() => render_fn(anchor, component));
+				commit();
 			}
-
+		} else if (defer) {
-		if (defer) {
 			/** @type {Batch} */ (current_batch).add_callback(commit);
 		} else {
 			commit();