Merge remote-tracking branch 'upstream/main' into dev/const-boundary

.changeset/spotty-drinks-tan.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: allow for duplicate `var` declarations

LICENSE.md

@@ -1,4 +1,4 @@
-Copyright (c) 2016-2025 [these people](https://github.com/sveltejs/svelte/graphs/contributors)
+Copyright (c) 2016-2025 [Svelte Contributors](https://github.com/sveltejs/svelte/graphs/contributors)
 
 Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 

README.md

@@ -5,7 +5,7 @@
 	</picture>
 </a>
 
-[![license](https://img.shields.io/npm/l/svelte.svg)](LICENSE.md) [![Chat](https://img.shields.io/discord/457912077277855764?label=chat&logo=discord)](https://svelte.dev/chat)
+[![License](https://img.shields.io/npm/l/svelte.svg)](LICENSE.md) [![Chat](https://img.shields.io/discord/457912077277855764?label=chat&logo=discord)](https://svelte.dev/chat)
 
 ## What is Svelte?
 

benchmarking/benchmarks/reactivity/kairo/kairo_avoidable.js

@@ -20,12 +20,12 @@ function setup() {
 	return {
 		destroy,
 		run() {
-			$.flush_sync(() => {
+			$.flush(() => {
 				$.set(head, 1);
 			});
 			assert($.get(computed5) === 6);
 			for (let i = 0; i < 1000; i++) {
-				$.flush_sync(() => {
+				$.flush(() => {
 					$.set(head, i);
 				});
 				assert($.get(computed5) === 6);

benchmarking/benchmarks/reactivity/kairo/kairo_broad.js

@@ -25,12 +25,12 @@ function setup() {
 	return {
 		destroy,
 		run() {
-			$.flush_sync(() => {
+			$.flush(() => {
 				$.set(head, 1);
 			});
 			counter = 0;
 			for (let i = 0; i < 50; i++) {
-				$.flush_sync(() => {
+				$.flush(() => {
 					$.set(head, i);
 				});
 				assert($.get(last) === i + 50);

benchmarking/benchmarks/reactivity/kairo/kairo_deep.js

@@ -25,12 +25,12 @@ function setup() {
 	return {
 		destroy,
 		run() {
-			$.flush_sync(() => {
+			$.flush(() => {
 				$.set(head, 1);
 			});
 			counter = 0;
 			for (let i = 0; i < iter; i++) {
-				$.flush_sync(() => {
+				$.flush(() => {
 					$.set(head, i);
 				});
 				assert($.get(current) === len + i);

benchmarking/benchmarks/reactivity/kairo/kairo_diamond.js

@@ -28,13 +28,13 @@ function setup() {
 	return {
 		destroy,
 		run() {
-			$.flush_sync(() => {
+			$.flush(() => {
 				$.set(head, 1);
 			});
 			assert($.get(sum) === 2 * width);
 			counter = 0;
 			for (let i = 0; i < 500; i++) {
-				$.flush_sync(() => {
+				$.flush(() => {
 					$.set(head, i);
 				});
 				assert($.get(sum) === (i + 1) * width);

benchmarking/benchmarks/reactivity/kairo/kairo_mux.js

@@ -22,13 +22,13 @@ function setup() {
 		destroy,
 		run() {
 			for (let i = 0; i < 10; i++) {
-				$.flush_sync(() => {
+				$.flush(() => {
 					$.set(heads[i], i);
 				});
 				assert($.get(splited[i]) === i + 1);
 			}
 			for (let i = 0; i < 10; i++) {
-				$.flush_sync(() => {
+				$.flush(() => {
 					$.set(heads[i], i * 2);
 				});
 				assert($.get(splited[i]) === i * 2 + 1);

benchmarking/benchmarks/reactivity/kairo/kairo_repeated.js

@@ -25,13 +25,13 @@ function setup() {
 	return {
 		destroy,
 		run() {
-			$.flush_sync(() => {
+			$.flush(() => {
 				$.set(head, 1);
 			});
 			assert($.get(current) === size);
 			counter = 0;
 			for (let i = 0; i < 100; i++) {
-				$.flush_sync(() => {
+				$.flush(() => {
 					$.set(head, i);
 				});
 				assert($.get(current) === i * size);

benchmarking/benchmarks/reactivity/kairo/kairo_triangle.js

@@ -38,13 +38,13 @@ function setup() {
 		destroy,
 		run() {
 			const constant = count(width);
-			$.flush_sync(() => {
+			$.flush(() => {
 				$.set(head, 1);
 			});
 			assert($.get(sum) === constant);
 			counter = 0;
 			for (let i = 0; i < 100; i++) {
-				$.flush_sync(() => {
+				$.flush(() => {
 					$.set(head, i);
 				});
 				assert($.get(sum) === constant - width + i * width);

benchmarking/benchmarks/reactivity/kairo/kairo_unstable.js

@@ -25,13 +25,13 @@ function setup() {
 	return {
 		destroy,
 		run() {
-			$.flush_sync(() => {
+			$.flush(() => {
 				$.set(head, 1);
 			});
 			assert($.get(current) === 40);
 			counter = 0;
 			for (let i = 0; i < 100; i++) {
-				$.flush_sync(() => {
+				$.flush(() => {
 					$.set(head, i);
 				});
 			}

benchmarking/benchmarks/reactivity/mol_bench.js

@@ -51,11 +51,11 @@ function setup() {
 		 */
 		run(i) {
 			res.length = 0;
-			$.flush_sync(() => {
+			$.flush(() => {
 				$.set(B, 1);
 				$.set(A, 1 + i * 2);
 			});
-			$.flush_sync(() => {
+			$.flush(() => {
 				$.set(A, 2 + i * 2);
 				$.set(B, 2);
 			});

packages/svelte/CHANGELOG.md

@@ -1,5 +1,21 @@
 # svelte
 
+## 5.20.4
+
+### Patch Changes
+
+- fix: update types and inline docs for flushSync ([#15348](https://github.com/sveltejs/svelte/pull/15348))
+
+## 5.20.3
+
+### Patch Changes
+
+- fix: allow `@const` inside `#key` ([#15377](https://github.com/sveltejs/svelte/pull/15377))
+
+- fix: remove unnecessary `?? ''` on some expressions ([#15287](https://github.com/sveltejs/svelte/pull/15287))
+
+- fix: correctly override class attributes with class directives ([#15352](https://github.com/sveltejs/svelte/pull/15352))
+
 ## 5.20.2
 
 ### Patch Changes

packages/svelte/package.json

@@ -2,7 +2,7 @@
   "name": "svelte",
   "description": "Cybernetically enhanced web apps",
   "license": "MIT",
-  "version": "5.20.2",
+  "version": "5.20.4",
   "type": "module",
   "types": "./types/index.d.ts",
   "engines": {

packages/svelte/src/compiler/phases/2-analyze/index.js

@@ -267,11 +267,9 @@ export function analyze_module(ast, options) {
 			expression: null,
 			function_depth: 0,
 			has_props_rune: false,
-			instance_scope: /** @type {any} */ (null),
 			options: /** @type {ValidatedCompileOptions} */ (options),
 			parent_element: null,
-			reactive_statement: null,
-			reactive_statements: new Map()
+			reactive_statement: null
 		},
 		visitors
 	);
@@ -566,7 +564,7 @@ export function analyze_component(root, source, options) {
 										binding.declaration_kind !== 'import'
 									) {
 										binding.kind = 'state';
-										binding.mutated = binding.updated = true;
+										binding.mutated = true;
 									}
 								}
 							}
@@ -620,9 +618,7 @@ export function analyze_component(root, source, options) {
 				expression: null,
 				derived_state: [],
 				function_depth: scope.function_depth,
-				instance_scope: instance.scope,
-				reactive_statement: null,
-				reactive_statements: new Map()
+				reactive_statement: null
 			};
 
 			walk(/** @type {AST.SvelteNode} */ (ast), state, visitors);
@@ -684,9 +680,7 @@ export function analyze_component(root, source, options) {
 				parent_element: null,
 				has_props_rune: false,
 				ast_type: ast === instance.ast ? 'instance' : ast === template.ast ? 'template' : 'module',
-				instance_scope: instance.scope,
 				reactive_statement: null,
-				reactive_statements: analysis.reactive_statements,
 				component_slots: new Set(),
 				expression: null,
 				derived_state: [],
@@ -767,66 +761,40 @@ export function analyze_component(root, source, options) {
 		if (!should_ignore_unused) {
 			warn_unused(analysis.css.ast);
 		}
+	}
 
-		outer: for (const node of analysis.elements) {
-			if (node.metadata.scoped) {
-				// Dynamic elements in dom mode always use spread for attributes and therefore shouldn't have a class attribute added to them
-				// TODO this happens during the analysis phase, which shouldn't know anything about client vs server
-				if (node.type === 'SvelteElement' && options.generate === 'client') continue;
-
-				/** @type {AST.Attribute | undefined} */
-				let class_attribute = undefined;
-
-				for (const attribute of node.attributes) {
-					if (attribute.type === 'SpreadAttribute') {
-						// The spread method appends the hash to the end of the class attribute on its own
-						continue outer;
-					}
+	for (const node of analysis.elements) {
+		if (node.metadata.scoped && is_custom_element_node(node)) {
+			mark_subtree_dynamic(node.metadata.path);
+		}
 
-					if (attribute.type !== 'Attribute') continue;
-					if (attribute.name.toLowerCase() !== 'class') continue;
-					// The dynamic class method appends the hash to the end of the class attribute on its own
-					if (attribute.metadata.needs_clsx) continue outer;
+		let has_class = false;
+		let has_spread = false;
+		let has_class_directive = false;
 
-					class_attribute = attribute;
-				}
+		for (const attribute of node.attributes) {
+			// The spread method appends the hash to the end of the class attribute on its own
+			if (attribute.type === 'SpreadAttribute') {
+				has_spread = true;
+				break;
+			}
+			has_class_directive ||= attribute.type === 'ClassDirective';
+			has_class ||= attribute.type === 'Attribute' && attribute.name.toLowerCase() === 'class';
+		}
 
-				if (class_attribute && class_attribute.value !== true) {
-					if (is_text_attribute(class_attribute)) {
-						class_attribute.value[0].data += ` ${analysis.css.hash}`;
-					} else {
-						/** @type {AST.Text} */
-						const css_text = {
-							type: 'Text',
-							data: ` ${analysis.css.hash}`,
-							raw: ` ${analysis.css.hash}`,
-							start: -1,
-							end: -1
-						};
-
-						if (Array.isArray(class_attribute.value)) {
-							class_attribute.value.push(css_text);
-						} else {
-							class_attribute.value = [class_attribute.value, css_text];
-						}
+		// We need an empty class to generate the set_class() or class="" correctly
+		if (!has_spread && !has_class && (node.metadata.scoped || has_class_directive)) {
+			node.attributes.push(
+				create_attribute('class', -1, -1, [
+					{
+						type: 'Text',
+						data: '',
+						raw: '',
+						start: -1,
+						end: -1
 					}
-				} else {
-					node.attributes.push(
-						create_attribute('class', -1, -1, [
-							{
-								type: 'Text',
-								data: analysis.css.hash,
-								raw: analysis.css.hash,
-								start: -1,
-								end: -1
-							}
-						])
-					);
-					if (is_custom_element_node(node) && node.attributes.length === 1) {
-						mark_subtree_dynamic(node.metadata.path);
-					}
-				}
-			}
+				])
+			);
 		}
 	}
 

packages/svelte/src/compiler/phases/2-analyze/types.d.ts

@@ -1,7 +1,6 @@
 import type { Scope } from '../scope.js';
 import type { ComponentAnalysis, ReactiveStatement } from '../types.js';
 import type { AST, ExpressionMetadata, ValidatedCompileOptions } from '#compiler';
-import type { LabeledStatement } from 'estree';
 
 export interface AnalysisState {
 	scope: Scope;
@@ -23,9 +22,7 @@ export interface AnalysisState {
 	function_depth: number;
 
 	// legacy stuff
-	instance_scope: Scope;
 	reactive_statement: null | ReactiveStatement;
-	reactive_statements: Map<LabeledStatement, ReactiveStatement>;
 }
 
 export type Context<State extends AnalysisState = AnalysisState> = import('zimmerframe').Context<

packages/svelte/src/compiler/phases/2-analyze/visitors/Attribute.js

@@ -162,7 +162,7 @@ function get_delegated_event(event_name, handler, context) {
 			return unhoisted;
 		}
 
-		if (binding !== null && binding.initial !== null && !binding.updated && !binding.is_called) {
+		if (binding !== null && binding.initial !== null && !binding.updated) {
 			const binding_type = binding.initial.type;
 
 			if (

packages/svelte/src/compiler/phases/2-analyze/visitors/BindDirective.js

@@ -5,7 +5,7 @@ import {
 	is_text_attribute,
 	object
 } from '../../../utils/ast.js';
-import { validate_no_const_assignment } from './shared/utils.js';
+import { validate_assignment } from './shared/utils.js';
 import * as e from '../../../errors.js';
 import * as w from '../../../warnings.js';
 import { binding_properties } from '../../bindings.js';
@@ -158,7 +158,7 @@ export function BindDirective(node, context) {
 		return;
 	}
 
-	validate_no_const_assignment(node, node.expression, context.state.scope, true);
+	validate_assignment(node, node.expression, context.state);
 
 	const assignee = node.expression;
 	const left = object(assignee);
@@ -184,14 +184,6 @@ export function BindDirective(node, context) {
 		) {
 			e.bind_invalid_value(node.expression);
 		}
-
-		if (context.state.analysis.runes && binding?.kind === 'each') {
-			e.each_item_invalid_assignment(node);
-		}
-
-		if (binding?.kind === 'snippet') {
-			e.snippet_parameter_assignment(node);
-		}
 	}
 
 	if (node.name === 'group') {