feat: allow changing response http status code from handleError

.changeset/seven-mangos-cheat.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': minor
+---
+
+feat: allow returning a custom HTTP status code from the `handleError` hook

documentation/docs/30-advanced/20-hooks.md

@@ -185,8 +185,9 @@ If an [unexpected error](errors#Unexpected-errors) is thrown during loading, ren
 
 - you can log the error
 - you can generate a custom representation of the error that is safe to show to users, omitting sensitive details like messages and stack traces. The returned value, which defaults to `{ message }`, becomes the value of `$page.error`.
+- you can customise the status code of the response
 
-For errors thrown from your code (or library code called by your code) the status will be 500 and the message will be "Internal Error". While `error.message` may contain sensitive information that should not be exposed to users, `message` is safe (albeit meaningless to the average user).
+For errors thrown from your code (or library code called by your code) the status will default to 500 and the message will default to "Internal Error". While `error.message` may contain sensitive information that should not be exposed to users, `message` is safe (albeit meaningless to the average user).
 
 To add more information to the `$page.error` object in a type-safe way, you can customize the expected shape by declaring an `App.Error` interface (which must include `message: string`, to guarantee sensible fallback behavior). This allows you to — for example — append a tracking ID for users to quote in correspondence with your technical support staff:
 

packages/kit/src/utils/error.js

@@ -25,9 +25,17 @@ export function normalize_error(error) {
 
 /**
  * @param {unknown} error
+ * @returns {number}
  */
 export function get_status(error) {
-	return error instanceof HttpError || error instanceof SvelteKitError ? error.status : 500;
+	if (error instanceof HttpError || error instanceof SvelteKitError) {
+		return error.status;
+	}
+	// For overrides / custom error objects
+	if (typeof error === 'object' && error !== null && 'status' in error) {
+		return /** @type {{ status?: number }} */ (error).status ?? 500;
+	}
+	return 500;
 }
 
 /**

packages/kit/test/apps/basics/src/routes/errors/custom-error/+server.js

@@ -0,0 +1,10 @@
+class CustomError extends Error {
+	constructor(message, errorOpts) {
+		super(message, errorOpts);
+		this.status = 422;
+	}
+}
+
+export function GET() {
+	throw new CustomError('Custom error');
+}

packages/kit/test/apps/basics/test/server.test.js

@@ -452,6 +452,11 @@ test.describe('Errors', () => {
 		expect(await response.text()).toMatch('thisvariableisnotdefined is not defined');
 	});
 
+	test('custom error object', async ({ request }) => {
+		const response = await request.get('/errors/custom-error');
+		expect(response.status()).toBe(422);
+	});
+
 	test('returns 400 when accessing a malformed URI', async ({ page }) => {
 		const response = await page.goto('/%c0%ae%c0%ae/etc/passwd');
 		if (process.env.DEV) {