Fix Svelte 5 slots change

.changeset/nine-carpets-doubt.md

@@ -0,0 +1,5 @@
+---
+'@astrojs/svelte': minor
+---
+
+Bumps Svelte 5 peer dependency to `^5.0.0-next.190` and support the latest slots/snippets API

packages/integrations/svelte/client-v5.js

@@ -1,8 +1,4 @@
-import { hydrate, mount, unmount } from 'svelte';
-import { add_snippet_symbol } from 'svelte/internal/client';
-
-// Allow a slot to be rendered as a snippet (dev validation only)
-const tagSlotAsSnippet = import.meta.env.DEV ? add_snippet_symbol : (s) => s;
+import { createRawSnippet, hydrate, mount, unmount } from 'svelte';
 
 export default (element) => {
 	return async (Component, props, slotted, { client }) => {
@@ -11,11 +7,16 @@ export default (element) => {
 		let children = undefined;
 		let $$slots = undefined;
 		for (const [key, value] of Object.entries(slotted)) {
+			$$slots ??= {};
 			if (key === 'default') {
-				children = createSlotDefinition(key, value);
+				$$slots.default = true;
+				children = createRawSnippet(() => ({
+					render: () => `<astro-slot>${value}</astro-slot>`,
+				}));
 			} else {
-				$$slots ??= {};
-				$$slots[key] = createSlotDefinition(key, value);
+				$$slots[key] = createRawSnippet(() => ({
+					render: () => `<astro-slot name="${key}">${value}</astro-slot>`,
+				}));
 			}
 		}
 
@@ -33,18 +34,3 @@ export default (element) => {
 		element.addEventListener('astro:unmount', () => unmount(component), { once: true });
 	};
 };
-
-function createSlotDefinition(key, children) {
-	/**
-	 * @param {Comment} $$anchor A comment node for slots in Svelte 5
-	 */
-	const fn = ($$anchor, _$$slotProps) => {
-		const parent = $$anchor.parentNode;
-		const el = document.createElement('div');
-		el.innerHTML = `<astro-slot${
-			key === 'default' ? '' : ` name="${key}"`
-		}>${children}</astro-slot>`;
-		parent.insertBefore(el.children[0], $$anchor);
-	};
-	return tagSlotAsSnippet(fn);
-}

packages/integrations/svelte/package.json

@@ -61,7 +61,7 @@
   },
   "peerDependencies": {
     "astro": "^4.0.0",
-    "svelte": "^4.0.0 || ^5.0.0-next.90",
+    "svelte": "^4.0.0 || ^5.0.0-next.190",
     "typescript": "^5.3.3"
   },
   "engines": {

packages/integrations/svelte/server-v5.js

@@ -1,9 +1,6 @@
-import { add_snippet_symbol } from 'svelte/internal/server';
+import { createRawSnippet } from 'svelte';
 import { render } from 'svelte/server';
 
-// Allow a slot to be rendered as a snippet (dev validation only)
-const tagSlotAsSnippet = import.meta.env.DEV ? add_snippet_symbol : (s) => s;
-
 function check(Component) {
 	// Svelte 5 generated components always accept these two props
 	const str = Component.toString();
@@ -21,22 +18,27 @@ async function renderToStaticMarkup(Component, props, slotted, metadata) {
 	let children = undefined;
 	let $$slots = undefined;
 	for (const [key, value] of Object.entries(slotted)) {
+		$$slots ??= {};
 		if (key === 'default') {
-			children = tagSlotAsSnippet(() => `<${tagName}>${value}</${tagName}>`);
+			$$slots.default = true;
+			children = createRawSnippet(() => ({
+				render: () => `<${tagName}>${value}</${tagName}>`,
+			}));
 		} else {
-			$$slots ??= {};
-			$$slots[key] = tagSlotAsSnippet(() => `<${tagName} name="${key}">${value}</${tagName}>`);
+			$$slots[key] = createRawSnippet(() => ({
+				render: () => `<${tagName} name="${key}">${value}</${tagName}>`,
+			}));
 		}
 	}
 
-	const { html } = render(Component, {
+	const result = render(Component, {
 		props: {
 			...props,
 			children,
 			$$slots,
 		},
 	});
-	return { html };
+	return { html: result.body };
 }
 
 export default {