What rendering errors does handleError in hooks.client.js catch?

[EmilTholin]

This interesting question was asked in the Discord chat.

This following setup throws an error that is caught by handleError in hooks.client.js:

// src/hooks.client.js
/** @type {import('@sveltejs/kit').HandleClientError} */
export function handleError({ error, event }) {
    console.log('Client-side handle error!');

    return {
        message: 'Whoops!'
    };
}

// src/routes/+page.js
import { browser } from '$app/environment';

export function load() {
    if (browser) throw new Error('Ouch!');

    return {};
}

<!-- src/routes/+page.svelte -->
<script>
  export let data;
</script>

If we remove the error in load above and change +page.svelte to the following instead...

<!-- src/routes/+page.svelte -->
<script>
  export let data;

  if (typeof window !== 'undefined') throw new Error('Man!');
</script>

... the error is not caught by handleError in hooks.client.js.

The documentation states that "If an unexpected error is thrown during loading or rendering, this function will be called...". Am I misunderstanding something about how handleError works in the client, or should perhaps the documentation be rephrased somewhat?

[technopahadi]

This should be answered or docs be fixed (if no such case)!

[Pensarfeo]

I have the same issue!