docs: handle immutable headers error (#12543)

* docs: handle immutable headers error * Update documentation/docs/30-advanced/20-hooks.md Co-authored-by: Simon H <[email protected]> --------- Co-authored-by: Tee Ming <[email protected]> Co-authored-by: Simon H <[email protected]>
sveltejs · Jan 22, 2025 · cc6dace · cc6dace
1 parent d9f1522
commit cc6dace
Showing 1 changed file with 7 additions and 0 deletions.
diff --git a/documentation/docs/30-advanced/20-hooks.md b/documentation/docs/30-advanced/20-hooks.md
@@ -67,6 +67,13 @@ export async function handle({ event, resolve }) {
 	event.locals.user = await getUserInformation(event.cookies.get('sessionid'));
 
 	const response = await resolve(event);
+
+	// Note that modifying response headers isn't always safe.
+	// Response objects can have immutable headers
+	// (e.g. Response.redirect() returned from an endpoint).
+	// Modifying immutable headers throws a TypeError.
+	// In that case, clone the response or avoid creating a
+	// response object with immutable headers.
 	response.headers.set('x-custom-header', 'potato');
 
 	return response;