Re: [csswg-drafts] [css-values] attr()'s url type seems wrong (#5079)

> Proposing: Make `<url>` type (`attr(name type(<url>))`) invalid in `attr()` during parse time.

I know I originally said:

> I wouldn't object to just making it invalid (parse-time).

But now that we have [argument grammars](https://drafts.csswg.org/css-values-5/#argument-grammar), I think we should drop the "parse time" part. Otherwise, to enforce a check against the type() _parse time_, we would have to make `type()` part of the argument grammar, meaning e.g. `attr(name type(var(--my-type)))` is impossible forever, which is sad. The [spread syntax](https://drafts.csswg.org/css-values-5/#spread-syntax) would also need to be invalid in `attr()`.

I would amend the proposed resolution as follows: `Make <url> type (attr(name type(<url>))) invalid in attr()`, leaving "when" it's invalid up to the general rules in [Argument Grammars and Spread Syntax](https://drafts.csswg.org/css-values-5/#early-resolution). This still fully addresses the original concern.

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Received on Friday, 11 April 2025 07:38:57 UTC