memory leak: detached nodes are kept when using transitions

[gyzerok]

Describe the bug

When using transitions something isn't cleaned up properly resulting in detached nodes memory leak.

This was already fixed once in #12719, so seems to be a regression due to some changes. I am wondering if it's even possible to have a test or something for it to prevent future regressions.

Reproduction

REPL

1. Take snapshot
2. Click button multiple times
3. Take snapshot again
4. Repeat and observe h1 leaking

Logs

System Info

Chrome 132.0.6834.160 (Official Build) (arm64)
Svelte 5.19.7

Severity

annoyance

[brunnerh]

This does not reproduce for me, at most singular elements are detached and nothing changes in regards to elements in subsequent snapshots.

Do you have some extension that maybe is messing with the DOM?
(E.g. those relating to translations can do that.)

[gyzerok]

@brunnerh not using chrome as my daily driver, so it's just a clean installation without any extensions. Are you sure you are taking snapshot of the right VM instance inside devtools? For me it's a common mistake to forget to record the correct one when doing it inside playground :)

[brunnerh]

Yes, I remembered that pitfall and made sure to avoid it (this time).

[gyzerok]

I also see retainer to be connected to animation

[gyzerok]

@brunnerh for me amount of detached nodes directly corresponds to the number of clicks I am doing

[gyzerok]

Also can confirm that if I remove in:fade transition than nothing leaks for me

[brunnerh]

So, given that you said that it could not be extensions, I thought "surely it's not the browser, right?" because mine was a bit out of date. Updated it and checked again...

Old Version: 131.0.6778.265
New Version: 132.0.6834.160

Thanks, Chrome 👍

[gyzerok]

@brunnerh looks like the same problem is in Safari as well