A css comment vanish if I comment out this line

[frederikhors]

Describe the bug

I created a new SvelteKit app (with command from https://kit.svelte.dev/docs#introduction-getting-started):

npm init --yes svelte@next my-app

Here the repo: https://github.com/frederikhors/iss-svelte-kit-tailwind-comments

I added Tailwind in this commit: https://github.com/frederikhors/iss-svelte-kit-tailwind-comments/commit/84906710c497d57c8394430a482049605c2c390f.

If you run the project with npm run dev (after npm install of course) it works (Tailwind works, there is a bg-red-500 in __layout.svelte).

What doesn't work is this crazy thing:

If you build with

rm -rf ./node_modules/.vite/ && rm -rf build && npm run build

and open the css in build/_app/assets/pages/__layout.svelte-[NUMBERS].css you can search for "I_need_this_comment" (which is a comment in src/app.css) and you can find it in the final css bundle.

Now if you comment out the first line in src/app.css enabling @tailwind base; and build again with the same command the comment is lost!!!

This drove me crazy!

Can you please help me understand what is going on?

Thanks!

Severity

serious, but I can work around it

[rmunn]

Looks like postcss may be what's removing the comments. I'd suggest opening an issue there, because I doubt this is a Svelte-Kit bug per se.

BTW, I experimented with your repro and found that if you move the @tailwind base line to below the comment, the comment isn't removed. I don't have time to pursue this further, but hopefully that will help you with narrowing this down.

I'll leave this issue open for now, just in case there really is a Svelte-Kit bug. But at the moment, I'm thinking it's something to do with postcss and not Svelte-Kit.

[frederikhors]

@rmunn thanks. I tried with the comment on the first line, it isn't removed, but I need other comments after the @tailwind base line too. 😢

[frederikhors]

@rmunn @ai answered postcss/postcss#1678 (comment). 😭

I opened this too: tailwindlabs/tailwindcss#6182

[dominikg]

tailwind author tracked this down to being an esbuild css minification issue: evanw/esbuild#1796

please follow up there.