[css-grid] Is `span` keyword excluded from Named Grid Lines <custom-ident>?

[tomalec]

The "7.2.1. Named Grid Lines" Section defines the syntax as just

[<custom-ident>*]

Where CSS Values for <custom-ident> says

Specifications using <custom-ident> must specify clearly what other keywords are excluded from <custom-ident>, if any

I would assume that span should be excluded not to collide with Line-based placement properties

Am I correct?

[tomalec]

Or are following valid?

grid-row: span; 
grid-column-end: span span 2;

[mrego]

I believe this is already covered at the end of the section:

In all the above productions, the additionally excludes the keyword span.

[tomalec]

Wow, that's it, but I didn't and wouldn't expect to see the explanation that far (7.2->9.3).

Per exceptio probat regulam, should I assume that all following occurrences of <custom-ident> (for example in 9.4) could potential contain span (it's not say they cannot) or are they just references to this specific instance of <custom-ident> that could not.

If the latter why can we cay that for in all cases <custom-ident> excludes span and if we say so I would rather provide such exception where we introduce it for the first time, not somewhere in the middle.

[tomalec]

My bad, sorry, It was mentioned closer, in 7.2.

In <line-names>, the <custom-ident> additionally excludes the keyword span

But maybe to avoid such confusion, and changing/adding a meaning retrospectively by ."In all the above productions". We could use just (already specified) <line-names> (for all <custom-ident> excluding the keyword span).

(Note, I'm willing to prepare PR if needed ;) )

[MatsPalmgren]

I think this general clause in [css-values] applies:
https://www.w3.org/TR/css3-values/#custom-idents

represents any valid CSS identifier that would not be misinterpreted as a pre-defined keyword in that property’s value definition

[mrego]

A few lines later the [css-values] spec says:

Specifications using must specify clearly what other keywords are excluded from , if any—for example by saying that any pre-defined keywords in that property’s value definition are excluded.

BTW, I remember a thread about this topic.

[fantasai]

A few lines later the [css-values] spec says:

Which is a conformance criterium on specs, not on implementations. ;)

We can't use <<line-names>> in place of <<custom-ident>> in section 9 because it includes the surrounding brackets, which aren't included as part of the value syntax in grid-area and its longhands.

I tweaked the wording of the statement a bit and move it into the line names section, let me know if that helps.

[tomalec]

Thanks :)