Making lightningcss optional peer dependency

[RobinTail]

Consider a Node.js project using vitest for testing.

There is absolutely no CSS, but vitest requires vite and it (even v8.0.0-beta.0) nevertheless requires lightningcss as a runtime dependency, that also installs detect-libc and 11 binary packages named lightningcss-[OS].

I made an experiment by overriding it in my pnpm config:

overrides:
  "lightningcss": "npm:empty-npm-package@1.0.0"

And worked well, so I presume that this package is not really used when no CSS present.

Therefore, for vite v8 I propose moving lightningcss to optional peer dependencies, so that consumers can install it only when needed.

[meduzen]

Agree with this. I use PostCSS with CSS Nano and don’t plan to change to LightningCSS for now. I just migrated a project to Vite 8, and used npm overrides as a workaround.

In your package.json:

    "devDependencies" : {
        "vite": "^8"
    },
    "overrides": {
        "lightningcss": "0.0.0"
    }

Then remove your package-lock.json and run npm install. You can now check your node_modules size (du -sh ./node_modules/* | sort -h) and see:

4.0K ./node_modules/lightningcss

Your Vite (8) config also needs to change css.minify by mentioning another minifier or setting it to false.