Update to svelte 5 (#12364)

Co-authored-by: bluwy <bjornlu.dev@gmail.com>

1 files changed, 79 insertions, 0 deletions

diff --git a/packages/integrations/svelte/client.svelte.js b/packages/integrations/svelte/client.svelte.js
new file mode 100644
index 000000000..1bff1bf24
--- /dev/null
+++ b/packages/integrations/svelte/client.svelte.js
@@ -0,0 +1,79 @@
+import { createRawSnippet, hydrate, mount, unmount } from 'svelte';
+
+/** @type {WrakMap<any, ReturnType<typeof createComponent>} */
+const existingApplications = new WeakMap();
+
+export default (element) => {
+	return async (Component, props, slotted, { client }) => {
+		if (!element.hasAttribute('ssr')) return;
+
+		let children = undefined;
+		let _$$slots = undefined;
+		let renderFns = {};
+
+		for (const [key, value] of Object.entries(slotted)) {
+			// Legacy slot support
+			_$$slots ??= {};
+			if (key === 'default') {
+				_$$slots.default = true;
+				children = createRawSnippet(() => ({
+					render: () => `<astro-slot>${value}</astro-slot>`,
+				}));
+			} else {
+				_$$slots[key] = createRawSnippet(() => ({
+					render: () => `<astro-slot name="${key}">${value}</astro-slot>`,
+				}));
+			}
+			// @render support for Svelte ^5.0
+			if (key === 'default') {
+				renderFns.children = createRawSnippet(() => ({
+					render: () => `<astro-slot>${value}</astro-slot>`,
+				}));
+			} else {
+				renderFns[key] = createRawSnippet(() => ({
+					render: () => `<astro-slot name="${key}">${value}</astro-slot>`,
+				}));
+			}
+		}
+
+		const resolvedProps = {
+			...props,
+			children,
+			$$slots: _$$slots,
+			...renderFns,
+		};
+		if (existingApplications.has(element)) {
+			existingApplications.get(element).setProps(resolvedProps);
+		} else {
+			const component = createComponent(Component, element, resolvedProps, client !== 'only');
+			existingApplications.set(element, component);
+			element.addEventListener('astro:unmount', () => component.destroy(), { once: true });
+		}
+	};
+};
+
+/**
+ * @param {any} Component
+ * @param {HTMLElement} target
+ * @param {Record<string, any>} props
+ * @param {boolean} shouldHydrate
+ */
+function createComponent(Component, target, props, shouldHydrate) {
+	let propsState = $state(props);
+	const bootstrap = shouldHydrate ? hydrate : mount;
+	const component = bootstrap(Component, { target, props: propsState });
+	return {
+		setProps(newProps) {
+			Object.assign(propsState, newProps);
+			// Remove props in `propsState` but not in `newProps`
+			for (const key in propsState) {
+				if (!(key in newProps)) {
+					delete propsState[key];
+				}
+			}
+		},
+		destroy() {
+			unmount(component);
+		},
+	};
+}