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fix(sveltekit): Align error status filtering and mechanism in handleErrorWithSentry #17157

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Merged
merged 1 commit into from
Jul 25, 2025
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fix(sveltekit): Align error status filtering and mechanism in handleErrorWithSentry #17157

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41 changes: 28 additions & 13 deletions packages/sveltekit/src/client/handleError.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -28,20 +28,35 @@ type SafeHandleServerErrorInput = Omit<HandleClientErrorInput, 'status' | 'messa
*
* @param handleError The original SvelteKit error handler.
*/
export function handleErrorWithSentry(handleError: HandleClientError = defaultErrorHandler): HandleClientError {
return (input: SafeHandleServerErrorInput): ReturnType<HandleClientError> => {
// SvelteKit 2.0 offers a reliable way to check for a 404 error:
if (input.status !== 404) {
captureException(input.error, {
mechanism: {
type: 'sveltekit',
handled: false,
},
});
export function handleErrorWithSentry(handleError?: HandleClientError): HandleClientError {
const errorHandler = handleError ?? defaultErrorHandler;

return (input: HandleClientErrorInput): ReturnType<HandleClientError> => {
if (is4xxError(input)) {
return errorHandler(input);
}

// We're extra cautious with SafeHandleServerErrorInput - this type is not compatible with HandleServerErrorInput
// @ts-expect-error - we're still passing the same object, just with a different (backwards-compatible) type
return handleError(input);
captureException(input.error, {
mechanism: {
type: 'sveltekit',
handled: !!handleError,
},
});

return errorHandler(input);
};
}

// 4xx are expected errors and thus we don't want to capture them
function is4xxError(input: SafeHandleServerErrorInput): boolean {
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Bug: Sentry Error Handling Breaks SvelteKit 1.x Compatibility

The handleErrorWithSentry function in both client and server modules introduces a type mismatch and breaks SvelteKit 1.x backwards compatibility. The input parameter's type was changed from SafeHandleServerErrorInput (where status and message are optional) to HandleServerErrorInput/HandleClientErrorInput (where they are required). This causes a TypeScript error and prevents SvelteKit 1.x from calling the function, as it may not provide these properties. The is4xxError helper function still expects an optional status, and existing @ts-expect-error comments confirm that 1.x compatibility is still expected.

Locations (2)

Fix in Cursor • Fix in Web

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@Lms24 Lms24 Jul 24, 2025 •
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This is incorrect. I did make the type change, to get rid of two/four ts-expect-error pragmas but we still use SafeHandle(Sever|Client)ErrorInput in the is4xxError checks respectively.

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Also, there's no kit@1 breakage because we just bail if we don't have a status on the client. On the server, we use the same fallback mechanism for detecting 404/"Not Found" errors but this isn't relevant for the client.

const { status } = input;

// Pre-SvelteKit 2.x, the status is not available,
// so we don't know if this is a 4xx error
if (!status) {
return false;
}

// SvelteKit 2.0 offers a reliable way to check for a Not Found error:
return status >= 400 && status < 500;
}
22 changes: 10 additions & 12 deletions packages/sveltekit/src/server-common/handleError.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -27,18 +27,18 @@ type SafeHandleServerErrorInput = Omit<HandleServerErrorInput, 'status' | 'messa
*
* @param handleError The original SvelteKit error handler.
*/
export function handleErrorWithSentry(handleError: HandleServerError = defaultErrorHandler): HandleServerError {
return async (input: SafeHandleServerErrorInput): Promise<void | App.Error> => {
if (isNotFoundError(input)) {
// We're extra cautious with SafeHandleServerErrorInput - this type is not compatible with HandleServerErrorInput
// @ts-expect-error - we're still passing the same object, just with a different (backwards-compatible) type
return handleError(input);
export function handleErrorWithSentry(handleError?: HandleServerError): HandleServerError {
const errorHandler = handleError ?? defaultErrorHandler;

return async (input: HandleServerErrorInput): Promise<void | App.Error> => {
if (is4xxError(input)) {
return errorHandler(input);
}

captureException(input.error, {
mechanism: {
type: 'sveltekit',
handled: false,
handled: !!handleError,
},
});

Expand All @@ -60,20 +60,18 @@ export function handleErrorWithSentry(handleError: HandleServerError = defaultEr
await flushIfServerless();
}

// We're extra cautious with SafeHandleServerErrorInput - this type is not compatible with HandleServerErrorInput
// @ts-expect-error - we're still passing the same object, just with a different (backwards-compatible) type
return handleError(input);
return errorHandler(input);
};
}

/**
* When a page request fails because the page is not found, SvelteKit throws a "Not found" error.
*/
function isNotFoundError(input: SafeHandleServerErrorInput): boolean {
function is4xxError(input: SafeHandleServerErrorInput): boolean {
const { error, event, status } = input;

// SvelteKit 2.0 offers a reliable way to check for a Not Found error:
if (status === 404) {
if (!!status && status >= 400 && status < 500) {
return true;
}

Expand Down
15 changes: 9 additions & 6 deletions packages/sveltekit/test/client/handleError.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,7 @@ const captureExceptionEventHint = {

const consoleErrorSpy = vi.spyOn(console, 'error').mockImplementation(_ => {});

describe('handleError', () => {
describe('handleError (client)', () => {
beforeEach(() => {
mockCaptureException.mockClear();
consoleErrorSpy.mockClear();
Expand Down Expand Up @@ -55,19 +55,22 @@ describe('handleError', () => {

expect(returnVal.message).toEqual('Whoops!');
expect(mockCaptureException).toHaveBeenCalledTimes(1);
expect(mockCaptureException).toHaveBeenCalledWith(mockError, captureExceptionEventHint);
expect(mockCaptureException).toHaveBeenCalledWith(mockError, {
mechanism: { handled: true, type: 'sveltekit' },
});

// Check that the default handler wasn't invoked
expect(consoleErrorSpy).toHaveBeenCalledTimes(0);
});
});

it("doesn't capture 404 errors", async () => {
it.each([400, 401, 402, 403, 404, 429, 499])("doesn't capture %s errors", async statusCode => {
const wrappedHandleError = handleErrorWithSentry(handleError);
const returnVal = (await wrappedHandleError({
error: new Error('404 Not Found'),
error: new Error(`Error with status ${statusCode}`),
event: navigationEvent,
status: 404,
message: 'Not Found',
status: statusCode,
message: `Error with status ${statusCode}`,
})) as any;

expect(returnVal.message).toEqual('Whoops!');
Expand Down
33 changes: 19 additions & 14 deletions packages/sveltekit/test/server-common/handleError.test.ts
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Expand Up @@ -19,7 +19,7 @@ const requestEvent = {} as RequestEvent;

const consoleErrorSpy = vi.spyOn(console, 'error').mockImplementation(_ => {});

describe('handleError', () => {
describe('handleError (server)', () => {
beforeEach(() => {
mockCaptureException.mockClear();
consoleErrorSpy.mockClear();
Expand All @@ -42,20 +42,23 @@ describe('handleError', () => {
expect(consoleErrorSpy).toHaveBeenCalledTimes(1);
});

it('doesn\'t capture "Not found" errors for incorrect navigations [Kit 2.x]', async () => {
const wrappedHandleError = handleErrorWithSentry();
it.each([400, 401, 402, 403, 404, 429, 499])(
"doesn't capture %s errors for incorrect navigations [Kit 2.x]",
async statusCode => {
const wrappedHandleError = handleErrorWithSentry();

const returnVal = await wrappedHandleError({
error: new Error('404 /asdf/123'),
event: requestEvent,
status: 404,
message: 'Not Found',
});
const returnVal = await wrappedHandleError({
error: new Error(`Error with status ${statusCode}`),
event: requestEvent,
status: statusCode,
message: `Error with status ${statusCode}`,
});

expect(returnVal).not.toBeDefined();
expect(mockCaptureException).toHaveBeenCalledTimes(0);
expect(consoleErrorSpy).toHaveBeenCalledTimes(1);
});
expect(returnVal).not.toBeDefined();
expect(mockCaptureException).toHaveBeenCalledTimes(0);
expect(consoleErrorSpy).toHaveBeenCalledTimes(1);
},
);

describe('calls captureException', () => {
it('invokes the default handler if no handleError func is provided', async () => {
Expand Down Expand Up @@ -87,7 +90,9 @@ describe('handleError', () => {

expect(returnVal.message).toEqual('Whoops!');
expect(mockCaptureException).toHaveBeenCalledTimes(1);
expect(mockCaptureException).toHaveBeenCalledWith(mockError, captureExceptionEventHint);
expect(mockCaptureException).toHaveBeenCalledWith(mockError, {
mechanism: { handled: true, type: 'sveltekit' },
});
// Check that the default handler wasn't invoked
expect(consoleErrorSpy).toHaveBeenCalledTimes(0);
});
Expand Down
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