SvelteKit: redirect() not working on server without disabling ssr

Question

I am using +layout.server.ts to redirect unauthenticated users from accessing authorized routes with this code:

/* +layout.server.ts */

export const load: PageServerLoad = async () => {
    // ...

    if (!isAuthenticatedUser && isAccessingAuthorizedRoute) {
        throw redirect(300, "/sign-in");
    }
}

But when I tested it by accessing an authorized url (let's say /user/profile), the browser gave me this error:

I didn't know what was the problem. After some workarounds and debugging, I found out the error was caused by server-side rendering. Because when I turned off the SSR in +layout.server.ts, redirect worked as expected and browser didn't throw any error. To confirm it, I also tried disabling SSR for a single page and only that page was redirecting rightly.

I am using +layout.server.ts to redirect unauthenticated users from accessing authorized routes with this code:

/* +layout.server.ts */

export const ssr = false;    // <= SSR is off

export const load: PageServerLoad = async () => {
    // ...

    if (!isAuthenticatedUser && isAccessingAuthorizedRoute) {
        // Working!
        throw redirect(300, "/sign-in");
    }
}

Why is this happening? I want to use redirect() without disabling SSR.

UPDATE: I also tried redirect() in +page.ts, +page.server.ts and +layout.ts. The same error also happened there when ssr was enabled. I don't think my client-side js code is responsible.

Answer 1

我发现了问题。罪魁祸首是我用于重定向的状态代码。

我提供了错误的状态代码300：

// ...

    if (!isAuthenticatedUser && isAccessingAuthorizedRoute) {
        // Wrong!
        throw redirect(300, "/sign-in");
    }

// ...

提供状态代码307解决了问题：

// From Svelte Documentation

export function load({ locals }) {
  if (!locals.user) {
        // Correct!
        throw redirect(307, '/login');
  }
}

现在，启用SSR后它可以正常工作。文档中没有解释为什么我必须使用状态代码307才能使其正常工作。我希望他们能在不久的将来对此进行解释。