[css-grid] `auto` and `span` should be invalid named cell tokens

[cdoublev]

grid-template[-areas]: "auto span" is valid whereas auto and span are not valid <custom-ident> in <grid-line> and <line-names>. Authors can still use them as named grid areas and reference their lines with auto|span-start|end though.

This rule seems mandatory for <grid-line> otherwise its parsing would be ambiguous, but not for <line-names>. Is it intentional or is it an oversight in parsing <string>+ of grid-template-areas?

A line name cannot be span or auto, i.e. the <custom-ident> in the <line-names> production excludes the keywords span and auto.

https://drafts.csswg.org/css-grid-2/#named-lines

In all the above productions, the <custom-ident> additionally excludes the keywords span and auto.

https://drafts.csswg.org/css-grid-2/#typedef-grid-row-start-grid-line

[tabatkins]

Intentional, just for consistency.

[cdoublev]

So grid-area: span is invalid to avoid ambiguity, and grid-template: [span] 1px is invalid for consistency. My question is: shouldn't grid-template-areas: "auto span" also be parsed as invalid, for consistency?

Considering this design...

<style>
  #container {
    display: grid;
    grid: "auto span";
  }
</style>
<div id="container">
  <div id="item"></div>
</div>

... I can place #item in row 1 / column 2 with grid-area: span-start but not with grid-area: span.

[Loirooriol]

Note that grid-template-areas: "auto span" will implicitly name lines as auto-start, auto-end, span-start and span-end. You can use these names in placement properties, so it's fine.

grid-template-rows: [span] 1px would name the line as span, but you can't refer to such line name in grid placement properties, so it makes no sense to allow that.

Banning grid-template-areas: "span" would actually be like banning grid-template-rows: [span-start] 1px [span-end].

[cdoublev]

I got it, thanks.