Using Vite inline styles causes hydration mismatch errors

[mashedkeyboard]

Describe the bug

When using a CSS import with ?inline in the URL and including it in the page using a svelte:element tag (to force a specific CSS file to be inlined in the page), a hydration error is created in Svelte 5 that did not exist in Svelte 4. This breaks the CSS, as the page hydration stops (the MRE doesn't significantly change as it's too minimal, but in the site I'm actually building, the styles mess up entirely!).

This appears to happen because the svelte:element node has no defined previous or next siblings.

Reproduction

See MRE repo - it's essentially just this file:
https://github.com/mashedkeyboard/test-hydration-inline-import/blob/main/src/routes/%2Bpage.svelte

Logs

No notable content in server console. Browser console as below:

Navigated to http://localhost:5173/
[vite] connecting... [client:495:8](http://localhost:5173/@vite/client)
[vite] connected. [client:614:14](http://localhost:5173/@vite/client)
Source map error: No sources are declared in this source map.
Resource URL: http://localhost:5173/node_modules/.vite/deps/chunk-UGBVNEQM.js?v=f8c6c012
Source Map URL: chunk-UGBVNEQM.js.map

Source map error: No sources are declared in this source map.
Resource URL: http://localhost:5173/node_modules/.vite/deps/svelte_legacy.js?v=f8c6c012
Source Map URL: svelte_legacy.js.map

Source map error: No sources are declared in this source map.
Resource URL: http://localhost:5173/node_modules/.vite/deps/svelte_internal_client.js?v=f8c6c012
Source Map URL: svelte_internal_client.js.map

Source map error: No sources are declared in this source map.
Resource URL: http://localhost:5173/node_modules/.vite/deps/svelte.js?v=f8c6c012
Source Map URL: svelte.js.map

[svelte] hydration_mismatch
Hydration failed because the initial UI does not match what was rendered on the server [client.js:2684:15](http://localhost:5173/node_modules/@sveltejs/kit/src/runtime/client/client.js?v=f8c6c012)

System Info

System:
    OS: Linux 6.1 Manjaro Linux
    CPU: (12) x64 AMD Ryzen 5 3600X 6-Core Processor
    Memory: 6.13 GB / 31.29 GB
    Container: Yes
    Shell: 3.7.1 - /bin/fish
  Binaries:
    Node: 18.20.4 - /bin/node
    Yarn: 1.22.22 - /bin/yarn
    npm: 10.8.3 - /bin/npm
    pnpm: 8.7.5 - ~/.local/share/nvm/v18.12.0/bin/pnpm
  Browsers:
    Chrome: Linux
    Chromium: 131.0.6778.69
  npmPackages:
    svelte: ^5.0.0 => 5.2.7

Severity

blocking an upgrade

[trueadm]

The reason this fails to hydrate is because it expects a sibling for the text node, but there isn't one because we're inside a <style> element:

https://github.com/sveltejs/svelte/blob/main/packages/svelte/src/internal/server/index.js#L73

[dummdidumm]

In the meantime, use @html instead:

<svelte:head>
    {@html '<styl' + `e> type="text/css">${something}</s` + 'tyle>'}
</svelte:head>

[mashedkeyboard]

In the meantime, use @html instead:

<svelte:head>
    {@html '<styl' + `e> type="text/css">${something}</s` + 'tyle>'}
</svelte:head>

Good idea - I hadn't thought of breaking up the style tag like that to avoid the regex match! Thanks, that's handy :)