Hydration sometimes causes static elements to be recreated rather than attached, causing animations to rerun

[fnimick]

Describe the bug

Some combinations of elements causes hydration to recreate a static element, causing animations to rerun.

I have provided the minimal example that I can produce. Changing any of the elements of this example causes the failure to no longer occur.

Reproduction

https://stackblitz.com/edit/sveltejs-kit-template-default-m8q8da?file=src%2Froutes%2F%2Bpage.svelte

Logs

No response

System Info

System:
    OS: macOS 13.1
    CPU: (10) arm64 Apple M1 Pro
    Memory: 75.61 MB / 16.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 16.17.1 - ~/.nvm/versions/node/v16.17.1/bin/node
    Yarn: 1.22.19 - ~/.yarn/bin/yarn
    npm: 8.15.0 - ~/.nvm/versions/node/v16.17.1/bin/npm
  Browsers:
    Chrome: 109.0.5414.87
    Firefox: 103.0.1
    Safari: 16.2
  npmPackages:
    @sveltejs/adapter-auto: ^1.0.0 => 1.0.1 
    @sveltejs/kit: ^1.0.0 => 1.1.3 
    svelte: ^3.54.0 => 3.55.1 
    vite: ^4.0.0 => 4.0.4 

Severity

serious, but I can work around it

Additional Information

No response

[Rich-Harris]

Unfortunately the repro no longer exists. I suspect this is fixed in Svelte 5, however

[dummdidumm]

Closing due to inactivity/lack of reproduction. If there's still a bug with Svelte 5, please open a new issue.

[fnimick]

This actually appears to have been fixed in Svelte 4, based on my investigation.

Here's another reproduction: https://stackblitz.com/edit/sveltejs-kit-template-default-28yuht?description=The%20default%20SvelteKit%20template,%20generated%20with%20create-svelte&file=src%2Froutes%2F%2Bpage.svelte,package.json,package-lock.json&title=SvelteKit%20Default%20Template

Switch this to svelte 3 latest in the package.json and you'll see the double hydration animation. With svelte 4, the problem does not appear.