Svelte 5 (alpha 62) nukes my SvelteKit app in DEV 💣

[svelte-kit-so-good]

Describe the bug

Title says it all ... but here is a video

• video starts with working case (alpha 61) and breaks with upgrade to alpha 62 (in dev ... works in prod)

pnpm_dev_alpha62_nukes_app.mp4

Reproduction

See video attached

Logs

No response

System Info

Svelte v5.0.0-next.62 (breaks)
Svelte v5.0.0-next.61 (works)

Severity

annoyance

[trueadm]

Which was the last version that worked?

[svelte-kit-so-good]

@trueadm alpha 61. Should've clarified but in the video I start with alpha 61 and it works. Upgrading to svelte@next moves to alpha 62 ... and breaks the app.

[trueadm]

@svelte-kit-so-good Can you try in a prod build? I'm wondering if this is related to #10464

[stolinski]

I am seeing this exact same error on v62 in a SK2 app. Trying a prod build now.

Edit: Running pnpm build & preview does work as expected. Only dev broken with the mismatch, filename error OP showed above.

[svelte-kit-so-good]

@stolinski yea I just checked ... it breaks with pnpm dev only in alpha 62. Using pnpm build works

[svelte-kit-so-good]

@svelte-kit-so-good Can you try in a prod build? I'm wondering if this is related to #10464

Just updated the video showing that alpha 62 works with prod but breaks in dev 👍

[Rich-Harris]

So we know where the error is — it's here:

svelte/packages/svelte/src/internal/client/dev/ownership.js

Lines 136 to 144 in d6e0fbd

	if (component && !owners.has(component)) {
	let original = [...owners][0];
	let message =
	// @ts-expect-error
	original.filename !== component.filename
	? // @ts-expect-error
	`${component.filename} mutated a value owned by ${original.filename}. This is strongly discouraged`
	: 'Mutating a value outside the component that created it is strongly discouraged';

What I don't understand yet is how we could wind up in that state, because owners should always have at least one member. If anyone is able to create a minimal repro that would be very helpful

[Conduitry]

sveltejs/kit#11878 Supposedly it's happening with a fresh SvelteKit project.

[JLAcostaEC]

sveltejs/kit#11878 Supposedly it's happening with a fresh SvelteKit project.

Same error here, right after updating to next63