Old page receives new page's props before swapping

[mattwigham]

Version:

• @inertiajs/svelte version: 2.0.0 and 1.3.0
• svelte version: 5.16.0

Describe the problem:

When navigating from one page to another, the old page component is briefly updated with the new page's props before the new page component is swapped in. This causes undefined errors since the old page doesn't have its expected props any longer.

I'm not sure if this is expected behavior, or if it's specific to Svelte 5. This happens when using $props() and $page.props.

Steps to reproduce:

Create two pages link to each other and each receives unique props.

// One.svelte

<script>
  import { Link } from "@inertiajs/svelte";
  let { propOne } = $props(); // set to "prop-one-value" on the server
  $inspect("One", propOne);
</script>

<Link href="/two">Two</Link>

// Two.svelte

<script>
  import { Link } from "@inertiajs/svelte";
  let { propTwo } = $props(); // set to "prop-two-value" on the server
  $inspect("Two", propTwo);
</script>

<Link href="/one">One</Link>

In the browser, navigate using the links and you'll see the following in the console.

init One prop-one-value
update One undefined
init Two prop-two-value
update Two undefined
init One prop-one-value
...

[youyoumu]

i bumped to this issue as well

[kre8or69]

I'm seeing this issue as well upgrading my app from pre 1.0 versions! Haven't been able to nail down which version has caused the bug though!

[kre8or69]

Was able to track down that the cause of this is indeed in the "@inertiajs/svelte": "1.3.0" release! I believe linked to this PR which changes things to support props being updated correctly when rendering the same component (allowing component reuse rather than re-rendering) #1969.

Seeing the same behavior where the props are updated and applied to the existing loaded component before the component is swapped to the new one causing an error upon re-render and skipping rendering the expected component all together.

Unsure how to test this further though as I'm not sure if its my setup is wrong or the changes just don't cover my use case!