postcss.plugin was deprecated. Migration guide

[tvvignesh]

Hi. I recently upgraded to "postcss": "8.2.1" with "rollup-plugin-postcss": "^4.0.0" and I see that I get a lot of warnings like this when minimize is set to true:

postcss({
	minimize: true
})

And eventually creates errors in the CSS files:

But if I don't add minimize I do not get these warnings, nor does anything fail.

Thanks.

[litt1e-p]

the same +1

[ludofischer]

I think removing minimize fixes the warning because the minimize option activates cssnano, and the current cssnano uses the old PostCSS API.

[andykenward]

Even without minimize I am getting that error #350 (comment). :(

I am using

"node": "14.6.0",
"npm": "7.8.0",

It's the conflict of postcss versions in

"rollup-plugin-postcss" : "^4.0.0"

using

"postcss": "8.x"

and

"cssnano": "^4.1.10"

using

"postcss": "^7.0.0"

Downgrading to rollup-plugin-postcss ^3.1.8 fixed the issue for me.