<attr-name> syntax

[Semigradsky]

In your tests I see that [ng:cloak] selector is valid. Also in https://csstree.github.io/docs/validator.html code is shown as valid:

[ng:cloak] {
  color: red
}

But in https://csstree.github.io/docs/syntax/#Type:attr-name ng:cloak value is shown as invalid.

As I see <ident-token> can't include colon symbol.

UPD: @lahmatiy is this non-standard behaviour in csstree?
As I see there is no ':' in diagram https://drafts.csswg.org/css-syntax/#ident-token-diagram

[lahmatiy]

Yep, you're right, that's non-standard behaviour which inherited from CSSO tests. I guess it was once important for Angular. However, I believe that no reason to support it now and it should be removed.

[lahmatiy]

Removed in 2.0.4