Fix length-zero-no-unit false positives for custom properties

[mbehzad]

What steps are needed to reproduce the bug?

Hi everyone,

CSS code:

.element {
  --offset: 0px;

  left: calc(var(--offset) + 50%);
}

stylelintrc config:

{
  "extends": "stylelint-config-standard"
}

Error:

2:14  ✖  Unexpected unit  length-zero-no-unit

Where left: calc(var(--offset) + 50%); with --offset: 0 (without unit) results to invalid left: calc(0 + 50%); css.
(mini repo to reproduce: https://github.com/mbehzad/reproduce-length-zero-no-unit-custom-properties-issue)

I think it is more safe to have the rule as

"length-zero-no-unit": [
      true,
      {
        "ignore": ["custom-properties"]
      }
    ],

If this makes sense, I can open a PR.
Cheers

What did you expect to happen?

Not removing the unit for this case: (--offset: 0px;)

What actually happened?

--offset: 0px; needs to be changed to --offset: 0;

[ybiquitous]

@mbehzad Thanks for opening the issue with the minimal reproduction. I can confirm the behavior you reported.

Considering the background (stylelint/stylelint#2586) where the ignore: ["custom-properties"] option was introduced, your proposal sounds to make sense.

[jeddy3]

Turning on the ignore: ["custom-properties"]` option SGTM. It'll make the config more permissive, so "patch" semver.