fix: class:directive not working with $$restProps (#15389)

* add spread to test

* fix #15386

* do no set cssHash on non-scoped element

* changeset

.changeset/lemon-cougars-buy.md

@@ -0,0 +1,6 @@
+---
+'svelte': patch
+---
+
+fix: class:directive not working with $$restProps #15386
+fix: spread add an useless cssHash on non-scoped element

packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/element.js

@@ -88,7 +88,9 @@ export function build_set_attributes(
 		element_id,
 		is_dynamic ? attributes_id : b.literal(null),
 		b.object(values),
-		context.state.analysis.css.hash !== '' && b.literal(context.state.analysis.css.hash),
+		element.metadata.scoped &&
+			context.state.analysis.css.hash !== '' &&
+			b.literal(context.state.analysis.css.hash),
 		preserve_attribute_case,
 		is_custom_element,
 		is_ignored(element, 'hydration_attribute_changed') && b.true

packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/element.js

@@ -368,9 +368,10 @@ function build_element_spread_attributes(
 		})
 	);
 
-	const css_hash = context.state.analysis.css.hash
-		? b.literal(context.state.analysis.css.hash)
-		: b.null;
+	const css_hash =
+		element.metadata.scoped && context.state.analysis.css.hash
+			? b.literal(context.state.analysis.css.hash)
+			: b.null;
 
 	const args = [object, css_hash, classes, styles, flags ? b.literal(flags) : undefined];
 	context.state.template.push(b.call('$.spread_attributes', ...args));

packages/svelte/src/internal/client/dom/elements/attributes.js

@@ -326,8 +326,16 @@ export function set_attributes(
 			continue;
 		}
 
+		if (key === 'class') {
+			var is_html = element.namespaceURI === 'http://www.w3.org/1999/xhtml';
+			set_class(element, is_html, value, css_hash, prev?.[CLASS], next[CLASS]);
+			current[key] = value;
+			current[CLASS] = next[CLASS];
+			continue;
+		}
+
 		var prev_value = current[key];
-		if (value === prev_value && key !== 'class') continue;
+		if (value === prev_value) continue;
 
 		current[key] = value;
 
@@ -377,9 +385,6 @@ export function set_attributes(
 				// @ts-ignore
 				element[`__${event_name}`] = undefined;
 			}
-		} else if (key === 'class') {
-			var is_html = element.namespaceURI === 'http://www.w3.org/1999/xhtml';
-			set_class(element, is_html, value, css_hash, prev?.[CLASS], next[CLASS]);
 		} else if (key === 'style' && value != null) {
 			element.style.cssText = value + '';
 		} else if (key === 'autofocus') {

packages/svelte/src/internal/client/dom/elements/class.js

@@ -6,8 +6,8 @@ import { hydrating } from '../hydration.js';
  * @param {boolean | number} is_html
  * @param {string | null} value
  * @param {string} [hash]
- * @param {Record<string, boolean>} [prev_classes]
- * @param {Record<string, boolean>} [next_classes]
+ * @param {Record<string, any>} [prev_classes]
+ * @param {Record<string, any>} [next_classes]
  * @returns {Record<string, boolean> | undefined}
  */
 export function set_class(dom, is_html, value, hash, prev_classes, next_classes) {
@@ -34,12 +34,10 @@ export function set_class(dom, is_html, value, hash, prev_classes, next_classes)
 		// @ts-expect-error need to add __className to patched prototype
 		dom.__className = value;
 	} else if (next_classes) {
-		prev_classes ??= {};
-
 		for (var key in next_classes) {
 			var is_present = !!next_classes[key];
 
-			if (is_present !== !!prev_classes[key]) {
+			if (prev_classes == null || is_present !== !!prev_classes[key]) {
 				dom.classList.toggle(key, is_present);
 			}
 		}

packages/svelte/tests/runtime-runes/samples/class-directive-mutations/_config.js

@@ -1,4 +1,4 @@
-import { flushSync } from 'svelte';
+import { flushSync, tick } from 'svelte';
 import { test } from '../../test';
 
 // This test counts mutations on hydration
@@ -16,7 +16,12 @@ export default test({
 
 	html: `
 		<main id="main" class="browser">
-			<div class="custom svelte-1cjqok6 foo bar"></div>
+			<div class="custom svelte-1cjqok6 foo bar" title="a title"></div>
+			<span class="svelte-1cjqok6 foo bar"></span>
+			<b class="custom foo bar"></b>
+			<i class="foo bar"></i>
+
+			<div class="custom svelte-1cjqok6 foo bar" title="a title"></div>
 			<span class="svelte-1cjqok6 foo bar"></span>
 			<b class="custom foo bar"></b>
 			<i class="foo bar"></i>
@@ -25,19 +30,97 @@ export default test({
 
 	ssrHtml: `
 		<main id="main">
-			<div class="custom svelte-1cjqok6 foo bar"></div>
+			<div class="custom svelte-1cjqok6 foo bar" title="a title"></div>
+			<span class="svelte-1cjqok6 foo bar"></span>
+			<b class="custom foo bar"></b>
+			<i class="foo bar"></i>
+
+			<div class="custom svelte-1cjqok6 foo bar" title="a title"></div>
 			<span class="svelte-1cjqok6 foo bar"></span>
 			<b class="custom foo bar"></b>
 			<i class="foo bar"></i>
 		</main>
 	`,
 
-	async test({ assert, component, instance }) {
+	async test({ target, assert, component, instance }) {
 		flushSync();
+		tick();
 		assert.deepEqual(instance.get_and_clear_mutations(), ['MAIN']);
 
 		component.foo = false;
 		flushSync();
-		assert.deepEqual(instance.get_and_clear_mutations(), ['DIV', 'SPAN', 'B', 'I']);
+		tick();
+		assert.deepEqual(
+			instance.get_and_clear_mutations(),
+			['DIV', 'SPAN', 'B', 'I', 'DIV', 'SPAN', 'B', 'I'],
+			'first mutation'
+		);
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<main id="main" class="browser">
+				<div class="custom svelte-1cjqok6 bar" title="a title"></div>
+				<span class="svelte-1cjqok6 bar"></span>
+				<b class="custom bar"></b>
+				<i class="bar"></i>
+
+				<div class="custom svelte-1cjqok6 bar" title="a title"></div>
+				<span class="svelte-1cjqok6 bar"></span>
+				<b class="custom bar"></b>
+				<i class="bar"></i>
+			</main>
+			`
+		);
+
+		component.foo = true;
+		flushSync();
+		assert.deepEqual(
+			instance.get_and_clear_mutations(),
+			['DIV', 'SPAN', 'B', 'I', 'DIV', 'SPAN', 'B', 'I'],
+			'second mutation'
+		);
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<main id="main" class="browser">
+				<div class="custom svelte-1cjqok6 bar foo" title="a title"></div>
+				<span class="svelte-1cjqok6 bar foo"></span>
+				<b class="custom bar foo"></b>
+				<i class="bar foo"></i>
+
+				<div class="custom svelte-1cjqok6 bar foo" title="a title"></div>
+				<span class="svelte-1cjqok6 bar foo"></span>
+				<b class="custom bar foo"></b>
+				<i class="bar foo"></i>
+			</main>
+			`
+		);
+
+		component.classname = 'another';
+		flushSync();
+		assert.deepEqual(
+			instance.get_and_clear_mutations(),
+			['DIV', 'B', 'DIV', 'B'],
+			'class mutation'
+		);
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<main id="main" class="browser">
+				<div class="another svelte-1cjqok6 foo bar" title="a title"></div>
+				<span class="svelte-1cjqok6 bar foo"></span>
+				<b class="another foo bar"></b>
+				<i class="bar foo"></i>
+
+				<div class="another svelte-1cjqok6 foo bar" title="a title"></div>
+				<span class="svelte-1cjqok6 bar foo"></span>
+				<b class="another foo bar"></b>
+				<i class="bar foo"></i>
+			</main>
+			`
+		);
 	}
 });

packages/svelte/tests/runtime-runes/samples/class-directive-mutations/main.svelte

@@ -33,10 +33,15 @@
 </script>
 
 <main id="main" class:browser>
-	<div class={classname} class:foo class:bar></div>
+	<div class={classname} title="a title" class:foo class:bar></div>
 	<span class:foo class:bar></span>
 	<b class={classname} class:foo class:bar></b>
 	<i class:foo class:bar></i>
+
+	<div {...{class:classname, title:"a title"}} class:foo class:bar></div>
+	<span {...{}} class:foo class:bar></span>
+	<b {...{class:classname}} class:foo class:bar></b>
+	<i {...{}} class:foo class:bar></i>	
 </main>
 
 <style>