fix: modulePreload false

[patak-dev]

Fixes #10773

Description

We currently share the same preload helper for injecting CSS stylesheets of dynamic imports. Even when modulePreload is set to false, we still need the preload import helper and preserve the CSS styles for the dynamically imported module.

We already had a test case for modulePreload: false, but one of the checks was wrong.

This fix isn't ideal, users that set modulePreload false would probably expect the import helper to be avoided. But at least the behavior is correct after this PR.

Related issue:

• Omit __vitePreload if dependency array is empty #13952

#13952 one isn't easy to solve as we need import.meta.url in the transform hook, and populate the deps for the dynamic import in generateBundle. If we don't find a good way to find if the preload helper is needed at transform time, maybe we could at least reduce the helper that is quite verbose now with no deps and then replace it back in generateBundle (even if we leave some white space to avoid messing with sourcemaps).

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[bluwy]

I think we can merge this as a stop gap for now. I also think it's not ideal, but I'm not really sure how to fix it. Maybe we can improve preloading overall later to tackle #13952, slim it down, different preloads for JS or CSS only, that PR to reduce preload deps string size etc at once.

[patak-dev]

Agreed. Not directly related, but the way we handle preloads may also get in the way to stabilize renderBuiltUrl. See #13834 (comment). I also don't know how to properly fix that one though if we need to wait until generateBundle. We could try add something to augmentChunkHash, using dynamicImports to precalculate all the URLs we'll need to inject in the marker.

[patak-dev]

/ecosystem-ci run

[vite-ecosystem-ci]

📝 Ran ecosystem CI: Open

suite	result
analogjs	❌ failure
astro	✅ success
histoire	❌ failure
iles	❌ failure
ladle	✅ success
laravel	✅ success
marko	✅ success
nuxt	✅ success
nx	❌ failure
previewjs	✅ success
qwik	✅ success
rakkas	✅ success
sveltekit	✅ success
unocss	✅ success
vite-plugin-pwa	✅ success
vite-plugin-ssr	✅ success
vite-plugin-react	✅ success
vite-plugin-react-pages	❌ failure
vite-plugin-react-swc	✅ success
vite-plugin-svelte	✅ success
vite-plugin-vue	✅ success
vite-setup-catalogue	✅ success
vitepress	✅ success
vitest	❌ failure

[patak-dev]

Same CI fails as in main, merging