support $$props and $$restProps for custom elements

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+* Fix `$$props` and `$$restProps` when compiling to a custom element ([#5482](https://github.com/sveltejs/svelte/issues/5482))
 * Add `Element` and `Node` to known globals ([#5586](https://github.com/sveltejs/svelte/issues/5586))
 
 ## 3.29.4

src/compiler/compile/render_dom/index.ts

@@ -474,7 +474,7 @@ export default function dom(
 
 					${css.code && b`this.shadowRoot.innerHTML = \`<style>${css.code.replace(/\\/g, '\\\\')}${options.dev ? `\n/*# sourceMappingURL=${css.map.toUrl()} */` : ''}</style>\`;`}
 
-					@init(this, { target: this.shadowRoot }, ${definition}, ${has_create_fragment ? 'create_fragment': 'null'}, ${not_equal}, ${prop_indexes}, ${dirty});
+					@init(this, { target: this.shadowRoot, props: @attribute_to_object(this.attributes) }, ${definition}, ${has_create_fragment ? 'create_fragment': 'null'}, ${not_equal}, ${prop_indexes}, ${dirty});
 
 					${dev_props_check}
 

src/runtime/internal/dom.ts

@@ -360,3 +360,11 @@ export class HtmlTag {
 		this.n.forEach(detach);
 	}
 }
+
+export function attribute_to_object(attributes) {
+	const result = {};
+	for (const attribute of attributes) {
+		result[attribute.name] = attribute.value;
+	}
+	return result;
+}

test/custom-elements/assert.js

@@ -31,3 +31,24 @@ export function equal(a, b, message) {
 export function ok(condition, message) {
 	if (!condition) throw new Error(message || `Expected ${condition} to be truthy`);
 }
+
+export function htmlEqual(actual, expected, message) {
+	return deepEqual(
+		normalizeHtml(window, actual),
+		normalizeHtml(window, expected),
+		message
+	);
+}
+
+function normalizeHtml(window, html) {
+	try {
+		const node = window.document.createElement('div');
+		node.innerHTML = html
+			.replace(/<!--.*?-->/g, '')
+			.replace(/>[\s\r\n]+</g, '><')
+			.trim();
+		return node.innerHTML.replace(/<\/?noscript\/?>/g, '');
+	} catch (err) {
+		throw new Error(`Failed to normalize HTML:\n${html}`);
+	}
+}

test/custom-elements/samples/$$props/main.svelte

@@ -0,0 +1,10 @@
+<svelte:options tag="custom-element"/>
+
+<script>
+	export let name;
+</script>
+
+<p>name: {name}</p>
+<p>$$props: {JSON.stringify($$props)}</p>
+<p>$$restProps: {JSON.stringify($$restProps)}</p>
+

test/custom-elements/samples/$$props/test.js

@@ -0,0 +1,13 @@
+import * as assert from 'assert';
+import './main.svelte';
+
+export default function (target) {
+	target.innerHTML = '<custom-element name="world" answer="42" test="svelte"></custom-element>';
+	const el = target.querySelector('custom-element');
+
+	assert.htmlEqual(el.shadowRoot.innerHTML, `
+		<p>name: world</p>
+		<p>$$props: {"name":"world","answer":"42","test":"svelte"}</p>
+		<p>$$restProps: {"answer":"42","test":"svelte"}</p>
+	`);
+}

test/js/samples/css-shadow-dom-keyframes/expected.js

@@ -1,6 +1,7 @@
 /* generated by Svelte vX.Y.Z */
 import {
 	SvelteElement,
+	attribute_to_object,
 	detach,
 	element,
 	init,
@@ -34,7 +35,18 @@ class Component extends SvelteElement {
 	constructor(options) {
 		super();
 		this.shadowRoot.innerHTML = `<style>div{animation:foo 1s}@keyframes foo{0%{opacity:0}100%{opacity:1}}</style>`;
-		init(this, { target: this.shadowRoot }, null, create_fragment, safe_not_equal, {});
+
+		init(
+			this,
+			{
+				target: this.shadowRoot,
+				props: attribute_to_object(this.attributes)
+			},
+			null,
+			create_fragment,
+			safe_not_equal,
+			{}
+		);
 
 		if (options) {
 			if (options.target) {