feat: more accurate render/mount/hydrate options (#12111)

make the props parameter optional only when there are no or only optional props

---------

Co-authored-by: Simon Holthausen <[email protected]>
Co-authored-by: Simon H <[email protected]>

Author: Rich-Harris

.changeset/famous-chairs-notice.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+feat: more accurate `render`/`mount`/`hydrate` options

packages/svelte/scripts/generate-types.js

@@ -30,7 +30,7 @@ await createBundle({
 		[`${pkg.name}/legacy`]: `${dir}/src/legacy/legacy-client.js`,
 		[`${pkg.name}/motion`]: `${dir}/src/motion/public.d.ts`,
 		[`${pkg.name}/reactivity`]: `${dir}/src/reactivity/index-client.js`,
-		[`${pkg.name}/server`]: `${dir}/src/server/index.js`,
+		[`${pkg.name}/server`]: `${dir}/src/server/index.d.ts`,
 		[`${pkg.name}/store`]: `${dir}/src/store/public.d.ts`,
 		[`${pkg.name}/transition`]: `${dir}/src/transition/public.d.ts`,
 		[`${pkg.name}/events`]: `${dir}/src/events/index.js`,

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

@@ -72,13 +72,20 @@ export function slot(anchor, slot_fn, slot_props, fallback_fn) {
  * @template {Record<string, any>} Props
  * @template {Record<string, any>} Exports
  * @param {import('../../index.js').ComponentType<import('../../index.js').SvelteComponent<Props>> | import('../../index.js').Component<Props, Exports, any>} component
- * @param {{
+ * @param {{} extends Props ? {
  * 		target: Document | Element | ShadowRoot;
  * 		anchor?: Node;
  * 		props?: Props;
  * 		events?: Record<string, (e: any) => any>;
  * 		context?: Map<any, any>;
  * 		intro?: boolean;
+ * 	}: {
+ * 		target: Document | Element | ShadowRoot;
+ * 		props: Props;
+ * 		anchor?: Node;
+ * 		events?: Record<string, (e: any) => any>;
+ * 		context?: Map<any, any>;
+ * 		intro?: boolean;
  * 	}} options
  * @returns {Exports}
  */
@@ -98,13 +105,20 @@ export function mount(component, options) {
  * @template {Record<string, any>} Props
  * @template {Record<string, any>} Exports
  * @param {import('../../index.js').ComponentType<import('../../index.js').SvelteComponent<Props>> | import('../../index.js').Component<Props, Exports, any>} component
- * @param {{
+ * @param {{} extends Props ? {
  * 		target: Document | Element | ShadowRoot;
  * 		props?: Props;
  * 		events?: Record<string, (e: any) => any>;
  *  	context?: Map<any, any>;
  * 		intro?: boolean;
  * 		recover?: boolean;
+ * 	} : {
+ * 		target: Document | Element | ShadowRoot;
+ * 		props: Props;
+ * 		events?: Record<string, (e: any) => any>;
+ *  	context?: Map<any, any>;
+ * 		intro?: boolean;
+ * 		recover?: boolean;
  * 	}} options
  * @returns {Exports}
  */

packages/svelte/src/internal/server/index.js

@@ -97,10 +97,10 @@ export let on_destroy = [];
  * Takes a component and returns an object with `body` and `head` properties on it, which you can use to populate the HTML when server-rendering your app.
  * @template {Record<string, any>} Props
  * @param {import('svelte').Component<Props> | import('svelte').ComponentType<import('svelte').SvelteComponent<Props>>} component
- * @param {{ props: Omit<Props, '$$slots' | '$$events'>; context?: Map<any, any> }} options
+ * @param {{ props?: Omit<Props, '$$slots' | '$$events'>; context?: Map<any, any> }} [options]
  * @returns {import('#server').RenderOutput}
  */
-export function render(component, options) {
+export function render(component, options = {}) {
 	const payload = create_payload();
 
 	const prev_on_destroy = on_destroy;

packages/svelte/src/server/index.d.ts

@@ -0,0 +1,21 @@
+import type { RenderOutput } from '#server';
+import type { ComponentProps, Component, SvelteComponent, ComponentType } from 'svelte';
+
+/**
+ * Only available on the server and when compiling with the `server` option.
+ * Takes a component and returns an object with `body` and `head` properties on it, which you can use to populate the HTML when server-rendering your app.
+ */
+export function render<
+	Comp extends SvelteComponent<any> | Component<any>,
+	Props extends ComponentProps<Comp> = ComponentProps<Comp>
+>(
+	...args: {} extends Props
+		? [
+				component: Comp extends SvelteComponent<any> ? ComponentType<Comp> : Comp,
+				options?: { props?: Omit<Props, '$$slots' | '$$events'>; context?: Map<any, any> }
+			]
+		: [
+				component: Comp extends SvelteComponent<any> ? ComponentType<Comp> : Comp,
+				options: { props: Omit<Props, '$$slots' | '$$events'>; context?: Map<any, any> }
+			]
+): RenderOutput;

packages/svelte/tests/types/component.ts

@@ -131,6 +131,13 @@ mount(NewComponent, {
 	intro: false,
 	recover: false
 });
+mount(
+	NewComponent,
+	// @ts-expect-error props missing
+	{ target: null as any }
+);
+// if component receives no args, props can be omitted
+mount(null as any as typeof SvelteComponent<{}>, { target: null as any });
 
 hydrate(NewComponent, {
 	target: null as any as Document | Element | ShadowRoot,
@@ -148,6 +155,13 @@ hydrate(NewComponent, {
 	intro: false,
 	recover: false
 });
+hydrate(
+	NewComponent,
+	// @ts-expect-error props missing
+	{ target: null as any }
+);
+// if component receives no args, props can be omitted
+hydrate(null as any as typeof SvelteComponent<{}>, { target: null as any });
 
 render(NewComponent, {
 	props: {
@@ -156,6 +170,14 @@ render(NewComponent, {
 		x: ''
 	}
 });
+// @ts-expect-error
+render(NewComponent);
+render(NewComponent, {
+	props: {
+		// @ts-expect-error
+		prop: 1
+	}
+});
 
 // --------------------------------------------------------------------------- interop
 
@@ -255,6 +277,13 @@ mount(functionComponent, {
 		readonly: 1
 	}
 });
+mount(
+	functionComponent,
+	// @ts-expect-error props missing
+	{ target: null as any }
+);
+// if component receives no args, props can be omitted
+mount(null as any as Component<{}>, { target: null as any });
 
 hydrate(functionComponent, {
 	target: null as any as Document | Element | ShadowRoot,
@@ -272,13 +301,33 @@ hydrate(functionComponent, {
 		binding: true
 	}
 });
+hydrate(
+	functionComponent,
+	// @ts-expect-error props missing
+	{ target: null as any }
+);
+// if component receives no args, props can be omitted
+hydrate(null as any as Component<{}>, { target: null as any });
 
 render(functionComponent, {
 	props: {
 		binding: true,
-		readonly: 'foo',
+		readonly: 'foo'
+	}
+});
+// @ts-expect-error
+render(functionComponent);
+render(functionComponent, {
+	// @ts-expect-error
+	props: {
+		binding: true
+	}
+});
+render(functionComponent, {
+	props: {
+		binding: true,
 		// @ts-expect-error
-		x: ''
+		readonly: 1
 	}
 });
 

packages/svelte/tsconfig.json

@@ -23,7 +23,7 @@
 			"svelte/internal/client": ["./src/internal/client/index.js"],
 			"svelte/legacy": ["./src/legacy/legacy-client.js"],
 			"svelte/motion": ["./src/motion/public.d.ts"],
-			"svelte/server": ["./src/server/index.js"],
+			"svelte/server": ["./src/server/index.d.ts"],
 			"svelte/store": ["./src/store/public.d.ts"],
 			"#compiler": ["./src/compiler/types/index.d.ts"],
 			"#client": ["./src/internal/client/types.d.ts"],

packages/svelte/types/index.d.ts

@@ -350,25 +350,39 @@ declare module 'svelte' {
 	 * Mounts a component to the given target and returns the exports and potentially the props (if compiled with `accessors: true`) of the component
 	 *
 	 * */
-	export function mount<Props extends Record<string, any>, Exports extends Record<string, any>>(component: ComponentType<SvelteComponent<Props, any, any>> | Component<Props, Exports, any>, options: {
+	export function mount<Props extends Record<string, any>, Exports extends Record<string, any>>(component: ComponentType<SvelteComponent<Props, any, any>> | Component<Props, Exports, any>, options: {} extends Props ? {
 		target: Document | Element | ShadowRoot;
 		anchor?: Node | undefined;
 		props?: Props | undefined;
 		events?: Record<string, (e: any) => any> | undefined;
 		context?: Map<any, any> | undefined;
 		intro?: boolean | undefined;
+	} : {
+		target: Document | Element | ShadowRoot;
+		props: Props;
+		anchor?: Node | undefined;
+		events?: Record<string, (e: any) => any> | undefined;
+		context?: Map<any, any> | undefined;
+		intro?: boolean | undefined;
 	}): Exports;
 	/**
 	 * Hydrates a component on the given target and returns the exports and potentially the props (if compiled with `accessors: true`) of the component
 	 *
 	 * */
-	export function hydrate<Props extends Record<string, any>, Exports extends Record<string, any>>(component: ComponentType<SvelteComponent<Props, any, any>> | Component<Props, Exports, any>, options: {
+	export function hydrate<Props extends Record<string, any>, Exports extends Record<string, any>>(component: ComponentType<SvelteComponent<Props, any, any>> | Component<Props, Exports, any>, options: {} extends Props ? {
 		target: Document | Element | ShadowRoot;
 		props?: Props | undefined;
 		events?: Record<string, (e: any) => any> | undefined;
 		context?: Map<any, any> | undefined;
 		intro?: boolean | undefined;
 		recover?: boolean | undefined;
+	} : {
+		target: Document | Element | ShadowRoot;
+		props: Props;
+		events?: Record<string, (e: any) => any> | undefined;
+		context?: Map<any, any> | undefined;
+		intro?: boolean | undefined;
+		recover?: boolean | undefined;
 	}): Exports;
 	/**
 	 * Unmounts a component that was previously mounted using `mount` or `hydrate`.
@@ -2110,14 +2124,25 @@ declare module 'svelte/reactivity' {
 }
 
 declare module 'svelte/server' {
+	import type { ComponentProps, Component, SvelteComponent, ComponentType } from 'svelte';
 	/**
 	 * Only available on the server and when compiling with the `server` option.
 	 * Takes a component and returns an object with `body` and `head` properties on it, which you can use to populate the HTML when server-rendering your app.
-	 * */
-	export function render<Props extends Record<string, any>>(component: import("svelte").Component<Props, any, string> | import("svelte").ComponentType<import("svelte").SvelteComponent<Props, any, any>>, options: {
-		props: Omit<Props, "$$slots" | "$$events">;
-		context?: Map<any, any> | undefined;
-	}): RenderOutput;
+	 */
+	export function render<
+		Comp extends SvelteComponent<any> | Component<any>,
+		Props extends ComponentProps<Comp> = ComponentProps<Comp>
+	>(
+		...args: {} extends Props
+			? [
+					component: Comp extends SvelteComponent<any> ? ComponentType<Comp> : Comp,
+					options?: { props?: Omit<Props, '$$slots' | '$$events'>; context?: Map<any, any> }
+				]
+			: [
+					component: Comp extends SvelteComponent<any> ? ComponentType<Comp> : Comp,
+					options: { props: Omit<Props, '$$slots' | '$$events'>; context?: Map<any, any> }
+				]
+	): RenderOutput;
 	interface RenderOutput {
 		/** HTML that goes into the `<head>` */
 		head: string;

playgrounds/demo/src/entry-server.ts

@@ -1,7 +1,5 @@
-// @ts-ignore
 import { render } from 'svelte/server';
 // @ts-ignore you need to create this file
 import App from './App.svelte';
 
-// @ts-ignore
-export const { head, body, css } = render(App, { props: { initialCount: 0 } });
+export const { head, body } = render(App);