4 files changed, 42 insertions, 24 deletions

diff --git a/packages/integrations/svelte/client.svelte.js b/packages/integrations/svelte/src/client.svelte.ts
index 3bc9369f8..102f99490 100644
--- a/packages/integrations/svelte/client.svelte.js
+++ b/packages/integrations/svelte/src/client.svelte.ts
@@ -1,15 +1,19 @@
 import { createRawSnippet, hydrate, mount, unmount } from 'svelte';
 
-/** @type {WeakMap<any, ReturnType<typeof createComponent>} */
-const existingApplications = new WeakMap();
+const existingApplications = new WeakMap<HTMLElement, ReturnType<typeof createComponent>>();
 
-export default (element) => {
-	return async (Component, props, slotted, { client }) => {
+export default (element: HTMLElement) => {
+	return async (
+		Component: any,
+		props: Record<string, any>,
+		slotted: Record<string, any>,
+		{ client }: Record<string, string>,
+	) => {
 		if (!element.hasAttribute('ssr')) return;
 
 		let children = undefined;
-		let _$$slots = undefined;
-		let renderFns = {};
+		let _$$slots: Record<string, any> | undefined = undefined;
+		let renderFns: Record<string, any> = {};
 
 		for (const [key, value] of Object.entries(slotted)) {
 			// Legacy slot support
@@ -43,7 +47,7 @@ export default (element) => {
 			...renderFns,
 		};
 		if (existingApplications.has(element)) {
-			existingApplications.get(element).setProps(resolvedProps);
+			existingApplications.get(element)!.setProps(resolvedProps);
 		} else {
 			const component = createComponent(Component, element, resolvedProps, client !== 'only');
 			existingApplications.set(element, component);
@@ -52,13 +56,13 @@ export default (element) => {
 	};
 };
 
-/**
- * @param {any} Component
- * @param {HTMLElement} target
- * @param {Record<string, any>} props
- * @param {boolean} shouldHydrate
- */
-function createComponent(Component, target, props, shouldHydrate) {
+
+function createComponent(
+	Component: any,
+	target: HTMLElement,
+	props: Record<string, any>,
+	shouldHydrate: boolean,
+) {
 	let propsState = $state(props);
 	const bootstrap = shouldHydrate ? hydrate : mount;
 	if (!shouldHydrate) {
@@ -66,7 +70,7 @@ function createComponent(Component, target, props, shouldHydrate) {
 	}
 	const component = bootstrap(Component, { target, props: propsState });
 	return {
-		setProps(newProps) {
+		setProps(newProps: Record<string, any>) {
 			Object.assign(propsState, newProps);
 			// Remove props in `propsState` but not in `newProps`
 			for (const key in propsState) {
diff --git a/packages/integrations/svelte/context.js b/packages/integrations/svelte/src/context.ts
index faec823a0..833755044 100644
--- a/packages/integrations/svelte/context.js
+++ b/packages/integrations/svelte/src/context.ts
@@ -1,8 +1,10 @@
-const contexts = new WeakMap();
+import type { SSRResult } from 'astro';
+
+const contexts = new WeakMap<SSRResult, { currentIndex: number; readonly id: string }>();
 
 const ID_PREFIX = 's';
 
-function getContext(rendererContextResult) {
+function getContext(rendererContextResult: SSRResult) {
 	if (contexts.has(rendererContextResult)) {
 		return contexts.get(rendererContextResult);
 	}
@@ -16,8 +18,8 @@ function getContext(rendererContextResult) {
 	return ctx;
 }
 
-export function incrementId(rendererContextResult) {
-	const ctx = getContext(rendererContextResult);
+export function incrementId(rendererContextResult: SSRResult) {
+	const ctx = getContext(rendererContextResult)!;
 	const id = ctx.id;
 	ctx.currentIndex++;
 	return id;
diff --git a/packages/integrations/svelte/server.js b/packages/integrations/svelte/src/server.ts
index 6ebb62adc..4b0fccb3d 100644
--- a/packages/integrations/svelte/server.js
+++ b/packages/integrations/svelte/src/server.ts
@@ -1,8 +1,10 @@
+import type { AstroComponentMetadata } from 'astro';
 import { createRawSnippet } from 'svelte';
 import { render } from 'svelte/server';
 import { incrementId } from './context.js';
+import type { RendererContext } from './types.js';
 
-function check(Component) {
+function check(Component: any) {
 	if (typeof Component !== 'function') return false;
 	// Svelte 5 generated components always accept a `$$payload` prop.
 	// This assumes that the SSR build does not minify it (which Astro enforces by default).
@@ -11,21 +13,27 @@ function check(Component) {
 	return Component.toString().includes('$$payload');
 }
 
-function needsHydration(metadata) {
+function needsHydration(metadata: AstroComponentMetadata) {
 	// Adjust how this is hydrated only when the version of Astro supports `astroStaticSlot`
 	return metadata.astroStaticSlot ? !!metadata.hydrate : true;
 }
 
-async function renderToStaticMarkup(Component, props, slotted, metadata) {
+async function renderToStaticMarkup(
+	this: RendererContext,
+	Component: any,
+	props: Record<string, any>,
+	slotted: Record<string, any>,
+	metadata: AstroComponentMetadata,
+) {
 	const tagName = needsHydration(metadata) ? 'astro-slot' : 'astro-static-slot';
 
 	let children = undefined;
-	let $$slots = undefined;
+	let $$slots: Record<string, any> | undefined = undefined;
 	let idPrefix;
 	if (this && this.result) {
 		idPrefix = incrementId(this.result);
 	}
-	const renderProps = {};
+	const renderProps: Record<string, any> = {};
 	for (const [key, value] of Object.entries(slotted)) {
 		// Legacy slot support
 		$$slots ??= {};
diff --git a/packages/integrations/svelte/src/types.ts b/packages/integrations/svelte/src/types.ts
new file mode 100644
index 000000000..86834336e
--- /dev/null
+++ b/packages/integrations/svelte/src/types.ts
@@ -0,0 +1,4 @@
+import type { SSRResult } from 'astro';
+export type RendererContext = {
+	result: SSRResult;
+};
\ No newline at end of file