`undefined` doesn't remove the class

[babakfp]

What version of Tailwind CSS are you using?

v3.1.8

Reproduction URL

https://play.tailwindcss.com/3kRy1GbH6z

Describe your issue

For example, I want to remove black: #000 from the colors object, So, I do this:

module.exports = {
  theme: {
    extend: {
      colors: {
        black: undefined,
      },
    },
  },
}

The issue is that the color black will still be suggested.

Maybe it's something related to tailwind itself because the key black still does exist in the colors object. Maybe tailwind can remove the item if the value is equal to undefined.

Thanks

[RobinMalfait]

Hey! Thank you for your bug report!
Much appreciated! 🙏

Going to leave it open and let @bradlc decide what to do with this. However, one thing you can do is set the value to null instead of undefined which doesn't suggest bg-black anymore.

https://play.tailwindcss.com/eHCuHrnxdL

[bradlc]

@RobinMalfait, I believe this is a bug in tailwindcss itself, in the getClassList function. I think we need to check for undefined values (and other falsy values?) in this loop? https://github.com/tailwindlabs/tailwindcss/blob/master/src/lib/setupContextUtils.js#L840-L845

[RobinMalfait]

Ah yep, good catch. I'll fix that!