sveltejs · Rich-Harris · Jul 16, 2025 · Jul 16, 2025
diff --git a/.changeset/two-terms-draw.md b/.changeset/two-terms-draw.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: ensure compiler state is reset before compilation
diff --git a/packages/svelte/src/compiler/index.js b/packages/svelte/src/compiler/index.js
@@ -20,7 +20,7 @@ export { default as preprocess } from './preprocess/index.js';
  */
 export function compile(source, options) {
 	source = remove_bom(source);
-	state.reset_warnings(options.warningFilter);
+	state.reset({ warning: options.warningFilter, filename: options.filename });
 	const validated = validate_component_options(options, '');
 
 	let parsed = _parse(source);
@@ -63,7 +63,7 @@ export function compile(source, options) {
  */
 export function compileModule(source, options) {
 	source = remove_bom(source);
-	state.reset_warnings(options.warningFilter);
+	state.reset({ warning: options.warningFilter, filename: options.filename });
 	const validated = validate_module_options(options, '');
 
 	const analysis = analyze_module(source, validated);
@@ -111,7 +111,7 @@ export function compileModule(source, options) {
  */
 export function parse(source, { modern, loose } = {}) {
 	source = remove_bom(source);
-	state.reset_warnings(() => false);
+	state.reset({ warning: () => false, filename: undefined });
 
 	const ast = _parse(source, loose);
 	return to_public_ast(source, ast, modern);

diff --git a/packages/svelte/src/compiler/migrate/index.js b/packages/svelte/src/compiler/migrate/index.js
@@ -9,7 +9,7 @@ import { parse } from '../phases/1-parse/index.js';
 import { regex_valid_component_name } from '../phases/1-parse/state/element.js';
 import { analyze_component } from '../phases/2-analyze/index.js';
 import { get_rune } from '../phases/scope.js';
-import { reset, reset_warnings } from '../state.js';
+import { reset, UNKNOWN_FILENAME } from '../state.js';
 import {
 	extract_identifiers,
 	extract_all_identifiers_from_expression,
@@ -134,7 +134,7 @@ export function migrate(source, { filename, use_ts } = {}) {
 			return start + style_placeholder + end;
 		});
 
-		reset_warnings(() => false);
+		reset({ warning: () => false, filename });
 
 		let parsed = parse(source);
 
@@ -145,7 +145,7 @@ export function migrate(source, { filename, use_ts } = {}) {
 			...validate_component_options({}, ''),
 			...parsed_options,
 			customElementOptions,
-			filename: filename ?? '(unknown)',
+			filename: filename ?? UNKNOWN_FILENAME,
 			experimental: {
 				async: true
 			}

diff --git a/packages/svelte/src/compiler/phases/2-analyze/index.js b/packages/svelte/src/compiler/phases/2-analyze/index.js
@@ -279,9 +279,8 @@ export function analyze_module(source, options) {
 		classes: new Map()
 	};
 
-	state.reset({
+	state.adjust({
 		dev: options.dev,
-		filename: options.filename,
 		rootDir: options.rootDir,
 		runes: true
 	});
@@ -531,12 +530,11 @@ export function analyze_component(root, source, options) {
 		async_deriveds: new Set()
 	};
 
-	state.reset({
+	state.adjust({
 		component_name: analysis.name,
 		dev: options.dev,
-		filename: options.filename,
 		rootDir: options.rootDir,
-		runes: true
+		runes
 	});
 
 	if (!runes) {

diff --git a/packages/svelte/src/compiler/phases/2-analyze/visitors/SvelteSelf.js b/packages/svelte/src/compiler/phases/2-analyze/visitors/SvelteSelf.js
@@ -3,7 +3,7 @@
 import { visit_component } from './shared/component.js';
 import * as e from '../../../errors.js';
 import * as w from '../../../warnings.js';
-import { filename } from '../../../state.js';
+import { filename, UNKNOWN_FILENAME } from '../../../state.js';
 
 /**
  * @param {AST.SvelteSelf} node
@@ -23,9 +23,9 @@ export function SvelteSelf(node, context) {
 	}
 
 	if (context.state.analysis.runes) {
-		const name = filename === '(unknown)' ? 'Self' : context.state.analysis.name;
+		const name = filename === UNKNOWN_FILENAME ? 'Self' : context.state.analysis.name;
 		const basename =
-			filename === '(unknown)'
+			filename === UNKNOWN_FILENAME
 				? 'Self.svelte'
 				: /** @type {string} */ (filename.split(/[/\\]/).pop());
 

diff --git a/packages/svelte/src/compiler/state.js b/packages/svelte/src/compiler/state.js
@@ -16,6 +16,11 @@ export let warnings = [];
  */
 export let filename;
 
+/**
+ * This is the fallback used when no filename is specified.
+ */
+export const UNKNOWN_FILENAME = '(unknown)';
+
 /**
  * The name of the component that is used in the `export default function ...` statement.
  */
@@ -80,15 +85,6 @@ export function pop_ignore() {
 	ignore_stack.pop();
 }
 
-/**
- *
- * @param {(warning: Warning) => boolean} fn
- */
-export function reset_warnings(fn = () => true) {
-	warning_filter = fn;
-	warnings = [];
-}
-
 /**
  * @param {AST.SvelteNode | NodeLike} node
  * @param {import('../constants.js').IGNORABLE_RUNTIME_WARNINGS[number]} code
@@ -99,21 +95,36 @@ export function is_ignored(node, code) {
 }
 
 /**
+ * Call this to reset the compiler state. Should be called before each compilation.
+ * @param {{ warning?: (warning: Warning) => boolean; filename: string | undefined }} state
+ */
+export function reset(state) {
+	dev = false;
+	runes = false;
+	component_name = UNKNOWN_FILENAME;
+	source = '';
+	locator = () => undefined;
+	filename = (state.filename ?? UNKNOWN_FILENAME).replace(/\\/g, '/');
+	warning_filter = state.warning ?? (() => true);
+	warnings = [];
+}
+
+/**
+ * Adjust the compiler state based on the provided state object.
+ * Call this after parsing and basic analysis happened.
  * @param {{
  *   dev: boolean;
- *   filename: string;
  *   component_name?: string;
  *   rootDir?: string;
  *   runes: boolean;
  * }} state
  */
-export function reset(state) {
+export function adjust(state) {
 	const root_dir = state.rootDir?.replace(/\\/g, '/');
-	filename = state.filename.replace(/\\/g, '/');
 
 	dev = state.dev;
 	runes = state.runes;
-	component_name = state.component_name ?? '(unknown)';
+	component_name = state.component_name ?? UNKNOWN_FILENAME;
 
 	if (typeof root_dir === 'string' && filename.startsWith(root_dir)) {
 		// make filename relative to rootDir

diff --git a/packages/svelte/src/compiler/utils/compile_diagnostic.js b/packages/svelte/src/compiler/utils/compile_diagnostic.js
@@ -61,7 +61,7 @@ export class CompileDiagnostic {
 		this.code = code;
 		this.message = message;
 
-		if (state.filename) {
+		if (state.filename !== state.UNKNOWN_FILENAME) {
 			this.filename = state.filename;
 		}
 

diff --git a/packages/svelte/tests/compiler-errors/test.ts b/packages/svelte/tests/compiler-errors/test.ts
@@ -1,5 +1,5 @@
 import * as fs from 'node:fs';
-import { assert, expect } from 'vitest';
+import { assert, expect, it } from 'vitest';
 import { compile, compileModule, type CompileError } from 'svelte/compiler';
 import { suite, type BaseTest } from '../suite';
 import { read_file } from '../helpers.js';
@@ -78,3 +78,15 @@ const { test, run } = suite<CompilerErrorTest>((config, cwd) => {
 export { test };
 
 await run(__dirname);
+
+it('resets the compiler state including filename', () => {
+	// start with something that succeeds
+	compile('<div>hello</div>', { filename: 'foo.svelte' });
+	// then try something that fails in the parsing stage
+	try {
+		compile('<p>hello<div>invalid</p>', { filename: 'bar.svelte' });
+		expect.fail('Expected an error');
+	} catch (e: any) {
+		expect(e.toString()).toContain('bar.svelte');
+	}
+});