cssnano removes empty custom properties

[jonnitto]

I opened also a bug report on the cssnano repo: cssnano/cssnano#1350

Describe the bug

In TailwindCSS, many custom properties are set, like --tw-grayscale: ; A class like .blur sets following CSS:

.blur {
  --tw-blur: blur(8px);
  filter: var(--tw-blur) var(--tw-brightness) var(--tw-contrast) var(--tw-grayscale) var(--tw-hue-rotate) var(--tw-invert) var(--tw-saturate) var(--tw-sepia) var(--tw-drop-shadow);
}

The problem is, if the class .grayscale is not used (who set a value, just like blur) the custom property gets removed and the class blur doesn't work anymore.

[epuluikis]

Same issue happens with the backdrop. 'Dummy' classes aren't being generated and as a result, backdrop doesn't work.

[jonnitto]

The bug is fixed, I'll close this issue as soon as the new version of cssnano is relased

[adamwathan]

Going to close since this is a cssnano bug and not a Tailwind bug 👍🏻