svelte5 error - $$props can not be used in runes mode

[rotimi-best]

Hi amazing team,

I just upgraded our codebase to svelte-5 and upon starting the project it throws this error:

    '    {#each additionalMetaTags as tag}\n' +
    '      <meta {...tag} />\n' +
    '    {/each}\n' +
    '  {/if}\n' +
    '\n' +
    '  {#if additionalLinkTags?.length}\n' +
    '    {#each additionalLinkTags as tag}\n' +
    '   '... 56 more characters
}
1:01:54 AM [vite] Pre-transform error: /classroomio/node_modules/.pnpm/[email protected]/node_modules/carbon-icons-svelte/lib/ChevronDown.svelte:6:16 Cannot use `$$props` in runes mode
1:01:54 AM [vite] Pre-transform error: /classroomio/node_modules/.pnpm/[email protected]/node_modules/carbon-icons-svelte/lib/TextAlignJustify.svelte:6:16 Cannot use `$$props` in runes mode
1:01:54 AM [vite] Pre-transform error: /classroomio/node_modules/.pnpm/[email protected]/node_modules/carbon-icons-svelte/lib/CloseLarge.svelte:6:16 Cannot use `$$props` in runes mode
1:01:54 AM [vite] Pre-transform error: /classroomio/node_modules/.pnpm/[email protected]/node_modules/carbon-icons-svelte/lib/MachineLearningModel.svelte:6:16 Cannot use `$$props` in runes mode
1:01:54 AM [vite] Pre-transform error: /classroomio/node_modules/.pnpm/[email protected]/node_modules/carbon-icons-svelte/lib/Forum.svelte:6:16 Cannot use `$$props` in runes mode
1:01:54 AM [vite] Pre-transform error: /classroomio/node_modules/.pnpm/[email protected]/node_modules/carbon-icons-svelte/lib/MapCenter.svelte:6:16 Cannot use `$$props` in runes mode

Steps to reproduce:

1. Clone repo and pull changes in branch chore: [DRAFT] migrating classroomio-com to svelte5 classroomio/classroomio#504
2. pnpm i
3. pnpm run dev --filter=classroomio-com
4. Open http://localhost:5174 in browser
5. You should see a 500 error page and the console should have this error

[brunnerh]

Please note that the compiler options affect external libraries as well.
If you enforce runes mode like this, you will, for the most part, not be able to import Svelte 3/4 libraries.

See these issue:

• [Svelte 5] Enabling Runes mode via compilerOptions incorrectly enforces it for external libraries sveltejs/svelte#9632
• Parametric compile options sveltejs/svelte#12415
  (The option currently cannot be dynamically applied unless the Vite plugin is used)

[rotimi-best]

@brunnerh Thanks then.

I will try using dynamicCompileOptions to exclude npm packages.

[metonym]

Thank you @brunnerh for addressing this!