Fix false positives for parametric mixins in selector-class-pattern

[SevenOutman]

Clearly describe the bug

Getting selector-class-pattern violations on LESS mixin definitions.

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

selector-class-pattern

What code is needed to reproduce the bug?

.my-mixin(@x: 5) {
  line-height: @x;
}

What stylelint configuration is needed to reproduce the bug?

{
  "rules": {
    // kebab-case
    'selector-class-pattern': '^[a-z0-9]+(-?[a-z0-9]+)*$'
  }
}

Which version of stylelint are you using?

13.12.0

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

CLI with stylelint "src/**/*.less" --syntax less"

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

Yes, it's related to LESS parametric mixins.

What did you expect to happen?

The selector-class-pattern rule ignores LESS mixins as documented

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

Styelint seems not to recognize it as a mixin.

Expected class selector ".my-mixin(@x: 5)" to      selector-class-pattern
match pattern "^[a-z0-9]+(-?[a-z0-9]+)*$"

[jeddy3]

@SevenOutman Thanks for the report and clear write-up.

Yes, it appears to be a bug. The heuristics in the isStandardSyntaxRule util need to be tweaked to catch this.

I've labelled the issue as ready to implement. Please consider contributing if you have time.

There are steps on how to fix a bug in a rule in the Developer guide.

[smile33]

Hope to fix it soon

[jeddy3]

@smile33 Please consider contributing if you have time.

There are steps on how to fix a bug in a rule in the Developer guide.

[mattxwang]

Looks like this should be closed by #5378, but feel free to re-open if needed!

[ybiquitous]

@mattxwang Good catch! Thank you 😄