fix(astro): add .js suffix to component entry modules

[ocavue]

Changes

When updating @sveltejs/vite-plugin-svelte from v5 to v6, the build fails with a parsing error:

[vite-plugin-svelte:compile] Unexpected token
file: astro-entry:/home/runner/work/astro/astro/packages/integrations/svelte/test/fixtures/async-rendering/src/components/Counter.svelte:1:9
  
   1 |  export { default } from "/home/runner/work/astro/astro/packages/integrations/svelte/test/fixtures/async-rendering/src/components/Counter.svelte"
                 ^

Root cause: pluginComponentEntry creates virtual modules like \0astro-entry:.../Component.svelte containing re-export statements.

In @sveltejs/vite-plugin-svelte v6, these modules are incorrectly treated as Svelte components due to the .svelte extension, causing parse errors.

In @sveltejs/vite-plugin-svelte v5, these modules are ignored because the module id contains \0 and get filtered out at createFilter.ts#L51.

See also: changelog for @sveltejs/vite-plugin-svelte v6.0.0

Solution: Add a .js suffix to virtual entry modules for non-JS files (like .svelte, .vue, etc.) to ensure that SFC plugins won't mistakenly process them as components.

This fix is applicable to all UI frameworks with custom file extensions, including Vue, Svelte, Marko, Riot, Ripple, and any other SFC framework that may arise in the future.

Testing

All existing tests pass.

Docs

No docs/changeset added because there are no changes to the public API. The pluginComponentEntry is just an implementation detail.

(I can add a changeset if the Astro team thinks it's necessary.)

[changeset-bot]

⚠️ No Changeset found

Latest commit: 985e764

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[github-actions]

⚠️ Package Trust Level Decreased

Caution

Decreased trust levels may indicate a higher risk of supply chain attacks. Please review these changes carefully.

📦 Package	🔒 Before	🔓 After
@cloudflare/unenv-preset	trusted-with-provenance	none
workerd	trusted-with-provenance	none
ts-api-utils	provenance	none
undici	provenance	none
miniflare	trusted-with-provenance	none
youch	provenance	none
@cloudflare/workerd-darwin-64	trusted-with-provenance	none
@cloudflare/workerd-darwin-arm64	trusted-with-provenance	none
@cloudflare/workerd-linux-64	trusted-with-provenance	none
@cloudflare/workerd-linux-arm64	trusted-with-provenance	none
@cloudflare/workerd-windows-64	trusted-with-provenance	none
wrangler	trusted-with-provenance	none

[ocavue]

see #14821