Add ignoreFunctions: [] to length-zero-no-unit

[zhawkins]

Clearly describe the bug

The length-zero-no-unit rule ignore: ["custom-properties"] option will only run on custom property declarations like:

a { --x: 0px; }

It doesn't handle var functions like:

font: var(--x, 0px);

I see it being discussed here: #4860 (comment) but don't see a corresponding new issue so I created one. Maybe this would be considered a new feature? 🤔

Which rule, if any, is the bug related to?

length-zero-no-unit

What code is needed to reproduce the bug?

.foo {
  --x: 0px;
  margin-top: var(--y, 0px);
}

What stylelint configuration is needed to reproduce the bug?

e.g.

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

Which version of stylelint are you using?

13.6.1

How are you running stylelint: CLI, PostCSS plugin, Node.js API?

VScode plugin with settings.json

    "stylelint.validate": ["scss"],
    "editor.codeActionsOnSave": {
        "source.fixAll.stylelint": true
    }

Does the bug relate to non-standard syntax (e.g. SCSS, Less etc.)?

No.

What did you expect to happen?

I expect the unit on 0px within var(--y, 0px); to be ignored.

What actually happened (e.g. what warnings or errors did you get)?

"The following warnings were flagged:"

   Expected unit (length-zero-no-unit)

[patric-eberle]

Same issue here. I MUST define a 0px value as fallback, but the linter triggers.

[jeddy3]

@zhawkins Thanks for creating the issue.

I suggest we add an ignoreFunctions: [] option for this to offer granular control to the user.

For example:

{
  "rules": {
    "length-zero-no-unit": [
      true,
       {
         "ignoreFunctions": ["var", "--custom"]
       }
    ]
  }
}

Would allow:

.foo {
  margin-top: var(--y, 0px);
  margin-bottom: --custom(0px);
}

I've labelled the issue as ready to implement. @zhawkins or @patric-eberle Please consider contributing if you have time.

There are steps on how to add a new option in the Developer guide.

[JuanFML]

Hi! I was looking at this and I was wondering if I could try to solve this issue as my first PR?

[hudochenkov]

@JuanFML of course! It would be great!