Fix false positives for interpolation in function-no-unknown

[m4thieulavoie]

This PR tweaks function-no-unknown so that ignoreFunctions are also supported in the custom properties syntax (e.g. --primary-color: #{custom-mixin(#fff)};

Which issue, if any, is this issue related to?

Fixes #5913

Is there anything in the PR that needs further explanation?

e.g. "No, it's self-explanatory."

[jeddy3]

@m4thieulavoie Thanks for the pull request.

As per #5913 (comment), let's check for #{ in the isStandardSyntaxFunction utility instead.

You'll want to include the accept tests in this testRule so that the postcss-scss custom syntax is used.

I suspect the changes you've made in this pull request to sanitize the node value will be useful in the stylelint-scss plugin if they add a scss/function-no-unknown rule. Let's revert them in this pull request, though.

[m4thieulavoie]

@m4thieulavoie Thanks for the pull request.

As per #5913 (comment), let's check for #{ in the isStandardSyntaxFunction utility instead.

You'll want to include the accept tests in this testRule so that the postcss-scss custom syntax is used.

I suspect the changes you've made in this pull request to sanitize the node value will be useful in the stylelint-scss plugin if they add a scss/function-no-unknown rule. Let's revert them in this pull request, though.

That should be done 👍 Let me know what you think!

[jeddy3]

Thank you for making the changes.

LGTM.

[ybiquitous]

@m4thieulavoie Thank you. LGTM 👍🏼

[ybiquitous]

Updated the changelog:

Fixed: function-no-unknown false positives for interpolation (#5914).