feat: ssr select value

.changeset/new-turkeys-exercise.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: correctly mark <option> elements as selected during SSR

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

@@ -1,3 +1,4 @@
+/** @import { Expression } from 'estree' */
 /** @import { Location } from 'locate-character' */
 /** @import { AST } from '#compiler' */
 /** @import { ComponentContext, ComponentServerTransformState } from '../types.js' */
@@ -6,8 +7,8 @@ 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 } from './shared/element.js';
-import { process_children, build_template } from './shared/utils.js';
+import { build_element_attributes, build_spread_object } from './shared/element.js';
+import { process_children, build_template, build_attribute_value } from './shared/utils.js';
 
 /**
  * @param {AST.RegularElement} node
@@ -71,21 +72,96 @@ export function RegularElement(node, context) {
 		);
 	}
 
-	if (body === null) {
-		process_children(trimmed, { ...context, state });
-	} else {
-		let id = body;
+	let select_with_value = false;
 
-		if (body.type !== 'Identifier') {
-			id = b.id(state.scope.generate('$$body'));
-			state.template.push(b.const(id, body));
+	if (node.name === 'select') {
+		const value = node.attributes.find(
+			(attribute) =>
+				(attribute.type === 'Attribute' || attribute.type === 'BindDirective') &&
+				attribute.name === 'value'
+		);
+		if (node.attributes.some((attribute) => attribute.type === 'SpreadAttribute')) {
+			select_with_value = true;
+			state.template.push(
+				b.stmt(
+					b.assignment(
+						'=',
+						b.id('$$payload.select_value'),
+						b.member(
+							build_spread_object(
+								node,
+								node.attributes.filter(
+									(attribute) =>
+										attribute.type === 'Attribute' ||
+										attribute.type === 'BindDirective' ||
+										attribute.type === 'SpreadAttribute'
+								),
+								context
+							),
+							'value',
+							false,
+							true
+						)
+					)
+				)
+			);
+		} else if (value) {
+			select_with_value = true;
+			const left = b.id('$$payload.select_value');
+			if (value.type === 'Attribute') {
+				state.template.push(
+					b.stmt(b.assignment('=', left, build_attribute_value(value.value, context)))
+				);
+			} else if (value.type === 'BindDirective') {
+				state.template.push(
+					b.stmt(
+						b.assignment(
+							'=',
+							left,
+							value.expression.type === 'SequenceExpression'
+								? b.call(value.expression.expressions[0])
+								: value.expression
+						)
+					)
+				);
+			}
 		}
+	}
+
+	if (
+		node.name === 'option' &&
+		!node.attributes.some(
+			(attribute) =>
+				attribute.type === 'SpreadAttribute' ||
+				((attribute.type === 'Attribute' || attribute.type === 'BindDirective') &&
+					attribute.name === 'value')
+		)
+	) {
+		const inner_state = { ...state, template: [], init: [] };
+		process_children(trimmed, { ...context, state: inner_state });
 
+		state.template.push(
+			b.stmt(
+				b.call(
+					'$.valueless_option',
+					b.id('$$payload'),
+					b.thunk(b.block([...inner_state.init, ...build_template(inner_state.template)]))
+				)
+			)
+		);
+	} else if (body !== null) {
 		// if this is a `<textarea>` value or a contenteditable binding, we only add
 		// the body if the attribute/binding is falsy
 		const inner_state = { ...state, template: [], init: [] };
 		process_children(trimmed, { ...context, state: inner_state });
 
+		let id = /** @type {Expression} */ (body);
+
+		if (body.type !== 'Identifier') {
+			id = b.id(state.scope.generate('$$body'));
+			state.template.push(b.const(id, body));
+		}
+
 		// Use the body expression as the body if it's truthy, otherwise use the inner template
 		state.template.push(
 			b.if(
@@ -94,6 +170,12 @@ export function RegularElement(node, context) {
 				b.block([...inner_state.init, ...build_template(inner_state.template)])
 			)
 		);
+	} else {
+		process_children(trimmed, { ...context, state });
+	}
+
+	if (select_with_value) {
+		state.template.push(b.stmt(b.assignment('=', b.id('$$payload.select_value'), b.void0)));
 	}
 
 	if (!node_is_void) {

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

@@ -202,6 +202,29 @@ export function build_element_attributes(node, context) {
 
 	if (has_spread) {
 		build_element_spread_attributes(node, attributes, style_directives, class_directives, context);
+		if (node.name === 'option') {
+			context.state.template.push(
+				b.call(
+					'$.maybe_selected',
+					b.id('$$payload'),
+					b.member(
+						build_spread_object(
+							node,
+							node.attributes.filter(
+								(attribute) =>
+									attribute.type === 'Attribute' ||
+									attribute.type === 'BindDirective' ||
+									attribute.type === 'SpreadAttribute'
+							),
+							context
+						),
+						'value',
+						false,
+						true
+					)
+				)
+			);
+		}
 	} else {
 		const css_hash = node.metadata.scoped ? context.state.analysis.css.hash : null;
 
@@ -236,6 +259,16 @@ export function build_element_attributes(node, context) {
 					);
 				}
 
+				if (node.name === 'option' && name === 'value') {
+					context.state.template.push(
+						b.call(
+							'$.maybe_selected',
+							b.id('$$payload'),
+							literal_value != null ? b.literal(/** @type {any} */ (literal_value)) : b.void0
+						)
+					);
+				}
+
 				continue;
 			}
 
@@ -260,6 +293,10 @@ export function build_element_attributes(node, context) {
 					b.call('$.attr', b.literal(name), value, is_boolean_attribute(name) && b.true)
 				);
 			}
+
+			if (name === 'value' && node.name === 'option') {
+				context.state.template.push(b.call('$.maybe_selected', b.id('$$payload'), value));
+			}
 		}
 	}
 
@@ -274,7 +311,7 @@ export function build_element_attributes(node, context) {
 
 /**
  * @param {AST.RegularElement | AST.SvelteElement} element
- * @param {AST.Attribute} attribute
+ * @param {AST.Attribute | AST.BindDirective} attribute
  */
 function get_attribute_name(element, attribute) {
 	let name = attribute.name;
@@ -286,6 +323,36 @@ function get_attribute_name(element, attribute) {
 	return name;
 }
 
+/**
+ * @param {AST.RegularElement | AST.SvelteElement} element
+ * @param {Array<AST.Attribute | AST.SpreadAttribute | AST.BindDirective>} attributes
+ * @param {ComponentContext} context
+ */
+export function build_spread_object(element, attributes, context) {
+	return b.object(
+		attributes.map((attribute) => {
+			if (attribute.type === 'Attribute') {
+				const name = get_attribute_name(element, attribute);
+				const value = build_attribute_value(
+					attribute.value,
+					context,
+					WHITESPACE_INSENSITIVE_ATTRIBUTES.includes(name)
+				);
+				return b.prop('init', b.key(name), value);
+			} else if (attribute.type === 'BindDirective') {
+				const name = get_attribute_name(element, attribute);
+				const value =
+					attribute.expression.type === 'SequenceExpression'
+						? b.call(attribute.expression.expressions[0])
+						: /** @type {Expression} */ (context.visit(attribute.expression));
+				return b.prop('init', b.key(name), value);
+			}
+
+			return b.spread(/** @type {Expression} */ (context.visit(attribute)));
+		})
+	);
+}
+
 /**
  *
  * @param {AST.RegularElement | AST.SvelteElement} element
@@ -336,21 +403,7 @@ function build_element_spread_attributes(
 		flags |= ELEMENT_PRESERVE_ATTRIBUTE_CASE;
 	}
 
-	const object = b.object(
-		attributes.map((attribute) => {
-			if (attribute.type === 'Attribute') {
-				const name = get_attribute_name(element, attribute);
-				const value = build_attribute_value(
-					attribute.value,
-					context,
-					WHITESPACE_INSENSITIVE_ATTRIBUTES.includes(name)
-				);
-				return b.prop('init', b.key(name), value);
-			}
-
-			return b.spread(/** @type {Expression} */ (context.visit(attribute)));
-		})
-	);
+	const object = build_spread_object(element, attributes, context);
 
 	const css_hash =
 		element.metadata.scoped && context.state.analysis.css.hash

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

@@ -535,3 +535,30 @@ export function derived(fn) {
 		return updated_value;
 	};
 }
+
+/**
+ *
+ * @param {Payload} payload
+ * @param {*} value
+ */
+export function maybe_selected(payload, value) {
+	return value === payload.select_value ? ' selected' : '';
+}
+
+/**
+ * @param {Payload} payload
+ * @param {() => void} children
+ * @returns {void}
+ */
+export function valueless_option(payload, children) {
+	var i = payload.out.length;
+
+	children();
+
+	var body = payload.out.slice(i);
+
+	if (body.replace(/<!---->/g, '') === payload.select_value) {
+		// replace '>' with ' selected>' (closing tag will be added later)
+		payload.out = payload.out.slice(0, i - 1) + ' selected>' + body;
+	}
+}

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

@@ -18,6 +18,7 @@ export class Payload {
 	css = new Set();
 	out = '';
 	uid = () => '';
+	select_value = undefined;
 
 	head = new HeadPayload();
 

packages/svelte/tests/runtime-legacy/samples/binding-circular/_config.js

@@ -1,9 +1,9 @@
 import { test } from '../../test';
 
 export default test({
-	html: `
+	ssrHtml: `
 		<select>
-			<option value="[object Object]">wheeee</option>
+			<option selected value="[object Object]">wheeee</option>
 		</select>
 	`
 });

packages/svelte/tests/runtime-legacy/samples/binding-indirect/_config.js

@@ -17,9 +17,9 @@ export default test({
 		return { tasks, selected: tasks[0] };
 	},
 
-	html: `
+	ssrHtml: `
 		<select>
-			<option value='[object Object]'>put your left leg in</option>
+			<option selected value='[object Object]'>put your left leg in</option>
 			<option value='[object Object]'>your left leg out</option>
 			<option value='[object Object]'>in, out, in, out</option>
 			<option value='[object Object]'>shake it all about</option>
@@ -36,7 +36,28 @@ export default test({
 		<p>shake it all about</p>
 	`,
 
-	async test({ assert, component, target, window }) {
+	async test({ assert, component, target, window, variant }) {
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<select>
+				<option ${variant === 'hydrate' ? 'selected ' : ''}value='[object Object]'>put your left leg in</option>
+				<option value='[object Object]'>your left leg out</option>
+				<option value='[object Object]'>in, out, in, out</option>
+				<option value='[object Object]'>shake it all about</option>
+			</select>
+
+			<label>
+				<input type='checkbox'> put your left leg in
+			</label>
+
+			<h2>Pending tasks</h2>
+			<p>put your left leg in</p>
+			<p>your left leg out</p>
+			<p>in, out, in, out</p>
+			<p>shake it all about</p>
+		`
+		);
 		const input = target.querySelector('input');
 		const select = target.querySelector('select');
 		const options = target.querySelectorAll('option');
@@ -57,7 +78,7 @@ export default test({
 			target.innerHTML,
 			`
 			<select>
-				<option value='[object Object]'>put your left leg in</option>
+				<option ${variant === 'hydrate' ? 'selected ' : ''}value='[object Object]'>put your left leg in</option>
 				<option value='[object Object]'>your left leg out</option>
 				<option value='[object Object]'>in, out, in, out</option>
 				<option value='[object Object]'>shake it all about</option>
@@ -94,7 +115,7 @@ export default test({
 			target.innerHTML,
 			`
 			<select>
-				<option value='[object Object]'>put your left leg in</option>
+				<option ${variant === 'hydrate' ? 'selected ' : ''}value='[object Object]'>put your left leg in</option>
 				<option value='[object Object]'>your left leg out</option>
 				<option value='[object Object]'>in, out, in, out</option>
 				<option value='[object Object]'>shake it all about</option>