Fix declaration-property-value-no-unknown false positives for env()

[romainmenke]

What steps are needed to reproduce the bug?

a {
  margin: env(safe-area-inset-bottom);
}

What Stylelint configuration is needed to reproduce the bug?

{
  "declaration-property-value-no-unknown": true,
}

How did you run Stylelint?

CLI and VSCode

Which version of Stylelint are you using?

15.0.0

What did you expect to happen?

I expected env() to be allowed in the same way as var()

What actually happened?

 ⚠  Unexpected unknown value "env(" for property "padding-bottom"  declaration-property-value-no-unknown

Does the bug relate to non-standard syntax?

No response

Proposal to fix the bug

No response

[Mouvedia]

That was to be expected. I'd say since env, clamp and the other unsupported css functions are included in css-functions-list which is already used by the function-no-unknown rule, we should reuse it until csstree gets patched.
The 2 PR that I sent 1 week ago will probably remain unanswered for a long time, so adding another wouldn't help; let's fix it on our side for now.

[jeddy3]

@romainmenke Thanks for the report and for using the template.

Let's:

• patch upstream (either in CSSTree or mdn-data, whichever is appropriate)
• workaround it here in Stylelint (as @Mouvedia mentioned)

For the latter, we can take the same approach as clamp/min/max, i.e. returning early if an env node is present.

Spec for env() for reference.

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.

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@Mouvedia Thank you for triaging the issue. Our conventions for triaging them consistently are in the maintainer guide.

[romainmenke]

• mdn-data already includes env() in the same way as it does var()
• opened a PR to passthrough env() in the css tree lexer