fix

Author: Rich-Harris

packages/svelte/src/compiler/index.js

@@ -106,7 +106,7 @@ export function compileModule(source, options) {
  */
 export function parse(source, { filename, rootDir, modern } = {}) {
 	state.reset_warning_filter(() => false);
-	state.reset(source, { filename, rootDir }); // TODO it's weird to require filename/rootDir here. reconsider the API
+	state.reset(source, { filename: filename ?? '(unknown)', rootDir });
 
 	const ast = _parse(source);
 	return to_public_ast(source, ast, modern);

packages/svelte/src/internal/client/runtime.js

@@ -230,11 +230,15 @@ function handle_error(error, effect, component_context) {
 	let current_context = component_context;
 
 	while (current_context !== null) {
-		/** @type {string} */
-		var filename = current_context.function?.[FILENAME];
+		if (DEV) {
+			/** @type {string} */
+			var filename = current_context.function?.[FILENAME];
 
-		const file = filename.split('/').pop();
-		component_stack.push(file);
+			if (filename) {
+				const file = filename.split('/').pop();
+				component_stack.push(file);
+			}
+		}
 
 		current_context = current_context.p;
 	}