From ac7e16002939f627bd961a9194e497f53ff466f9 Mon Sep 17 00:00:00 2001
From: LeeWxx <99359120+LeeWxx@users.noreply.github.com>
Date: Thu, 25 Sep 2025 01:35:51 +0900
Subject: [PATCH] fix: SSR scoped classes for <select value> elements (#16821)

* fix: preserve scoped classes on select during ssr

* test: cover select scoped class regression

* chore: changeset

* chore: format files after lint

* fix: unify <select> attribute handling and prevent double-await

* test: update renderer.select call order

* fix: restore scoped classes on <option>

* test: cover scoped class for <option>

* dry

* de-diff

* tweak changeset

---------

Co-authored-by: 7nik <kifiranet@gmail.com>
Co-authored-by: Rich Harris <rich.harris@vercel.com>
---
 .changeset/nasty-comics-play.md               |   5 +
 .../server/visitors/RegularElement.js         |  71 +++++-------
 .../server/visitors/shared/element.js         | 103 ++++++++++++++----
 .../svelte/src/internal/server/renderer.js    |  19 +++-
 .../src/internal/server/renderer.test.ts      |  18 +++
 .../option-scoped-class/_expected.html        |   2 +
 .../samples/option-scoped-class/main.svelte   |  10 ++
 .../select-value-scoped-class/_expected.html  |   1 +
 .../select-value-scoped-class/main.svelte     |   9 ++
 9 files changed, 172 insertions(+), 66 deletions(-)
 create mode 100644 .changeset/nasty-comics-play.md
 create mode 100644 packages/svelte/tests/server-side-rendering/samples/option-scoped-class/_expected.html
 create mode 100644 packages/svelte/tests/server-side-rendering/samples/option-scoped-class/main.svelte
 create mode 100644 packages/svelte/tests/server-side-rendering/samples/select-value-scoped-class/_expected.html
 create mode 100644 packages/svelte/tests/server-side-rendering/samples/select-value-scoped-class/main.svelte

diff --git a/.changeset/nasty-comics-play.md b/.changeset/nasty-comics-play.md
new file mode 100644
index 0000000000..b75c82c493
--- /dev/null
+++ b/.changeset/nasty-comics-play.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: SSR regression of processing attributes of `<select>` and `<option>`
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/RegularElement.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/RegularElement.js
index 14f48d1ce7..df3e2fc37f 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/RegularElement.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/RegularElement.js
@@ -7,11 +7,10 @@ import { is_void } from '../../../../../utils.js';
 import { dev, locator } from '../../../../state.js';
 import * as b from '#compiler/builders';
 import { clean_nodes, determine_namespace_for_children } from '../../utils.js';
-import { build_element_attributes, build_spread_object } from './shared/element.js';
+import { build_element_attributes, prepare_element_spread_object } from './shared/element.js';
 import {
 	process_children,
 	build_template,
-	build_attribute_value,
 	create_child_block,
 	PromiseOptimiser
 } from './shared/utils.js';
@@ -37,9 +36,27 @@ export function RegularElement(node, context) {
 
 	const optimiser = new PromiseOptimiser();
 
-	state.template.push(b.literal(`<${node.name}`));
-	const body = build_element_attributes(node, { ...context, state }, optimiser.transform);
-	state.template.push(b.literal(node_is_void ? '/>' : '>')); // add `/>` for XHTML compliance
+	// If this element needs special handling (like <select value> / <option>),
+	// avoid calling build_element_attributes here to prevent evaluating/awaiting
+	// attribute expressions twice. We'll handle attributes in the special branch.
+	const is_select_special =
+		node.name === 'select' &&
+		node.attributes.some(
+			(attribute) =>
+				((attribute.type === 'Attribute' || attribute.type === 'BindDirective') &&
+					attribute.name === 'value') ||
+				attribute.type === 'SpreadAttribute'
+		);
+	const is_option_special = node.name === 'option';
+	const is_special = is_select_special || is_option_special;
+
+	let body = /** @type {Expression | null} */ (null);
+	if (!is_special) {
+		// only open the tag in the non-special path
+		state.template.push(b.literal(`<${node.name}`));
+		body = build_element_attributes(node, { ...context, state }, optimiser.transform);
+		state.template.push(b.literal(node_is_void ? '/>' : '>')); // add `/>` for XHTML compliance
+	}
 
 	if ((node.name === 'script' || node.name === 'style') && node.fragment.nodes.length === 1) {
 		state.template.push(
@@ -95,27 +112,7 @@ export function RegularElement(node, context) {
 		);
 	}
 
-	if (
-		node.name === 'select' &&
-		node.attributes.some(
-			(attribute) =>
-				((attribute.type === 'Attribute' || attribute.type === 'BindDirective') &&
-					attribute.name === 'value') ||
-				attribute.type === 'SpreadAttribute'
-		)
-	) {
-		const attributes = build_spread_object(
-			node,
-			node.attributes.filter(
-				(attribute) =>
-					attribute.type === 'Attribute' ||
-					attribute.type === 'BindDirective' ||
-					attribute.type === 'SpreadAttribute'
-			),
-			context,
-			optimiser.transform
-		);
-
+	if (is_select_special) {
 		const inner_state = { ...state, template: [], init: [] };
 		process_children(trimmed, { ...context, state: inner_state });
 
@@ -124,7 +121,9 @@ export function RegularElement(node, context) {
 			b.block([...state.init, ...build_template(inner_state.template)])
 		);
 
-		const statement = b.stmt(b.call('$$renderer.select', attributes, fn));
+		const [attributes, ...rest] = prepare_element_spread_object(node, context, optimiser.transform);
+
+		const statement = b.stmt(b.call('$$renderer.select', attributes, fn, ...rest));
 
 		if (optimiser.expressions.length > 0) {
 			context.state.template.push(
@@ -137,19 +136,7 @@ export function RegularElement(node, context) {
 		return;
 	}
 
-	if (node.name === 'option') {
-		const attributes = build_spread_object(
-			node,
-			node.attributes.filter(
-				(attribute) =>
-					attribute.type === 'Attribute' ||
-					attribute.type === 'BindDirective' ||
-					attribute.type === 'SpreadAttribute'
-			),
-			context,
-			optimiser.transform
-		);
-
+	if (is_option_special) {
 		let body;
 
 		if (node.metadata.synthetic_value_node) {
@@ -167,7 +154,9 @@ export function RegularElement(node, context) {
 			);
 		}
 
-		const statement = b.stmt(b.call('$$renderer.option', attributes, body));
+		const [attributes, ...rest] = prepare_element_spread_object(node, context, optimiser.transform);
+
+		const statement = b.stmt(b.call('$$renderer.option', attributes, body, ...rest));
 
 		if (optimiser.expressions.length > 0) {
 			context.state.template.push(
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/element.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/element.js
index 3b5f2423a3..cfb87b0ce7 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/element.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/element.js
@@ -358,17 +358,86 @@ function build_element_spread_attributes(
 	context,
 	transform
 ) {
+	const args = prepare_element_spread(
+		element,
+		/** @type {Array<AST.Attribute | AST.SpreadAttribute | AST.BindDirective>} */ (attributes),
+		style_directives,
+		class_directives,
+		context,
+		transform
+	);
+
+	let call = b.call('$.attributes', ...args);
+
+	context.state.template.push(call);
+}
+
+/**
+ * Prepare args for $.attributes(...): compute object, css_hash, classes, styles and flags.
+ * @param {AST.RegularElement | AST.SvelteElement} element
+ * @param {ComponentContext} context
+ * @param {(expression: Expression, metadata: ExpressionMetadata) => Expression} transform
+ * @returns {[ObjectExpression,Literal | undefined, ObjectExpression | undefined, ObjectExpression | undefined, Literal | undefined]}
+ */
+export function prepare_element_spread_object(element, context, transform) {
+	/** @type {Array<AST.Attribute | AST.SpreadAttribute | AST.BindDirective>} */
+	const select_attributes = [];
+	/** @type {AST.ClassDirective[]} */
+	const class_directives = [];
+	/** @type {AST.StyleDirective[]} */
+	const style_directives = [];
+
+	for (const attribute of element.attributes) {
+		if (
+			attribute.type === 'Attribute' ||
+			attribute.type === 'BindDirective' ||
+			attribute.type === 'SpreadAttribute'
+		) {
+			select_attributes.push(attribute);
+		} else if (attribute.type === 'ClassDirective') {
+			class_directives.push(attribute);
+		} else if (attribute.type === 'StyleDirective') {
+			style_directives.push(attribute);
+		}
+	}
+
+	return prepare_element_spread(
+		element,
+		select_attributes,
+		style_directives,
+		class_directives,
+		context,
+		transform
+	);
+}
+
+/**
+ * Prepare args for $.attributes(...): compute object, css_hash, classes, styles and flags.
+ * @param {AST.RegularElement | AST.SvelteElement} element
+ * @param {Array<AST.Attribute | AST.SpreadAttribute | AST.BindDirective>} attributes
+ * @param {AST.StyleDirective[]} style_directives
+ * @param {AST.ClassDirective[]} class_directives
+ * @param {ComponentContext} context
+ * @param {(expression: Expression, metadata: ExpressionMetadata) => Expression} transform
+ * @returns {[ObjectExpression,Literal | undefined, ObjectExpression | undefined, ObjectExpression | undefined, Literal | undefined]}
+ */
+export function prepare_element_spread(
+	element,
+	attributes,
+	style_directives,
+	class_directives,
+	context,
+	transform
+) {
+	/** @type {ObjectExpression | undefined} */
 	let classes;
+	/** @type {ObjectExpression | undefined} */
 	let styles;
 	let flags = 0;
 
-	let has_await = false;
-
 	if (class_directives.length) {
-		const properties = class_directives.map((directive) => {
-			has_await ||= directive.metadata.expression.has_await;
-
-			return b.init(
+		const properties = class_directives.map((directive) =>
+			b.init(
 				directive.name,
 				directive.expression.type === 'Identifier' && directive.expression.name === directive.name
 					? b.id(directive.name)
@@ -376,24 +445,21 @@ function build_element_spread_attributes(
 							/** @type {Expression} */ (context.visit(directive.expression)),
 							directive.metadata.expression
 						)
-			);
-		});
+			)
+		);
 
 		classes = b.object(properties);
 	}
 
 	if (style_directives.length > 0) {
-		const properties = style_directives.map((directive) => {
-			has_await ||= directive.metadata.expression.has_await;
-
-			return b.init(
+		const properties = style_directives.map((directive) =>
+			b.init(
 				directive.name,
 				directive.value === true
 					? b.id(directive.name)
 					: build_attribute_value(directive.value, context, transform, true)
-			);
-		});
-
+			)
+		);
 		styles = b.object(properties);
 	}
 
@@ -406,17 +472,12 @@ function build_element_spread_attributes(
 	}
 
 	const object = build_spread_object(element, attributes, context, transform);
-
 	const css_hash =
 		element.metadata.scoped && context.state.analysis.css.hash
 			? b.literal(context.state.analysis.css.hash)
 			: undefined;
 
-	const args = [object, css_hash, classes, styles, flags ? b.literal(flags) : undefined];
-
-	let call = b.call('$.attributes', ...args);
-
-	context.state.template.push(call);
+	return [object, css_hash, classes, styles, flags ? b.literal(flags) : undefined];
 }
 
 /**
diff --git a/packages/svelte/src/internal/server/renderer.js b/packages/svelte/src/internal/server/renderer.js
index 6971f200a0..bbb43a6f3b 100644
--- a/packages/svelte/src/internal/server/renderer.js
+++ b/packages/svelte/src/internal/server/renderer.js
@@ -160,9 +160,16 @@ export class Renderer {
 	/**
 	 * @param {Record<string, any>} attrs
 	 * @param {(renderer: Renderer) => void} fn
+	 * @param {string | undefined} [css_hash]
+	 * @param {Record<string, boolean> | undefined} [classes]
+	 * @param {Record<string, string> | undefined} [styles]
+	 * @param {number | undefined} [flags]
+	 * @returns {void}
 	 */
-	select({ value, ...attrs }, fn) {
-		this.push(`<select${attributes(attrs)}>`);
+	select(attrs, fn, css_hash, classes, styles, flags) {
+		const { value, ...select_attrs } = attrs;
+
+		this.push(`<select${attributes(select_attrs, css_hash, classes, styles, flags)}>`);
 		this.child((renderer) => {
 			renderer.local.select_value = value;
 			fn(renderer);
@@ -173,9 +180,13 @@ export class Renderer {
 	/**
 	 * @param {Record<string, any>} attrs
 	 * @param {string | number | boolean | ((renderer: Renderer) => void)} body
+	 * @param {string | undefined} [css_hash]
+	 * @param {Record<string, boolean> | undefined} [classes]
+	 * @param {Record<string, string> | undefined} [styles]
+	 * @param {number | undefined} [flags]
 	 */
-	option(attrs, body) {
-		this.#out.push(`<option${attributes(attrs)}`);
+	option(attrs, body, css_hash, classes, styles, flags) {
+		this.#out.push(`<option${attributes(attrs, css_hash, classes, styles, flags)}`);
 
 		/**
 		 * @param {Renderer} renderer
diff --git a/packages/svelte/src/internal/server/renderer.test.ts b/packages/svelte/src/internal/server/renderer.test.ts
index 88fbee855a..8e9a377a5b 100644
--- a/packages/svelte/src/internal/server/renderer.test.ts
+++ b/packages/svelte/src/internal/server/renderer.test.ts
@@ -207,6 +207,24 @@ test('selects an option with an implicit value', () => {
 	);
 });
 
+test('select merges scoped css hash with static class', () => {
+	const component = (renderer: Renderer) => {
+		renderer.select(
+			{ class: 'foo', value: 'foo' },
+			(renderer) => {
+				renderer.option({ value: 'foo' }, (renderer) => renderer.push('foo'));
+			},
+			'svelte-hash'
+		);
+	};
+
+	const { head, body } = Renderer.render(component as unknown as Component);
+	expect(head).toBe('');
+	expect(body).toBe(
+		'<!--[--><select class="foo svelte-hash"><option value="foo" selected>foo</option></select><!--]-->'
+	);
+});
+
 describe('async', () => {
 	beforeAll(() => {
 		enable_async_mode_flag();
diff --git a/packages/svelte/tests/server-side-rendering/samples/option-scoped-class/_expected.html b/packages/svelte/tests/server-side-rendering/samples/option-scoped-class/_expected.html
new file mode 100644
index 0000000000..b30e5ff4a1
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/option-scoped-class/_expected.html
@@ -0,0 +1,2 @@
+<select><option class="opt svelte-1l69ci" value="foo" selected>foo</option></select>
+
diff --git a/packages/svelte/tests/server-side-rendering/samples/option-scoped-class/main.svelte b/packages/svelte/tests/server-side-rendering/samples/option-scoped-class/main.svelte
new file mode 100644
index 0000000000..657f1e949d
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/option-scoped-class/main.svelte
@@ -0,0 +1,10 @@
+<select value="foo">
+	<option class="opt" value="foo">foo</option>
+</select>
+
+<style>
+	option {
+		color: red;
+	}
+</style>
+
diff --git a/packages/svelte/tests/server-side-rendering/samples/select-value-scoped-class/_expected.html b/packages/svelte/tests/server-side-rendering/samples/select-value-scoped-class/_expected.html
new file mode 100644
index 0000000000..d74fc96d9c
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/select-value-scoped-class/_expected.html
@@ -0,0 +1 @@
+<select class="foo svelte-18avu97"><option value="foo" selected>foo</option></select>
diff --git a/packages/svelte/tests/server-side-rendering/samples/select-value-scoped-class/main.svelte b/packages/svelte/tests/server-side-rendering/samples/select-value-scoped-class/main.svelte
new file mode 100644
index 0000000000..9ad3a6b4d2
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/select-value-scoped-class/main.svelte
@@ -0,0 +1,9 @@
+<select class="foo" value="foo">
+	<option value="foo">foo</option>
+</select>
+
+<style>
+	select {
+		color: red;
+	}
+</style>