[css-cascade-7] @sheet - allow nested @sheet statements?

[KurtCattiSchmidt]

This was discussed a bit in April 2023 but didn't land on a specific resolution for this behavior: #5629 (comment)

If you have a file named my_css.css as follows:

* { font-family: serif; }
@sheet foo {
  @sheet bar {
    font-family: sans-serif;
  }
  font-family: serif;
}

Should this be allowed? If so, it could follow the precedent for @layer and allow nested sheets via the . syntax:

<link rel="my_css.css" sheet="foo.bar" />

As mentioned in the above CSSWG discussion, we'd need to be explicit about how @import works in these cases (which would need some careful considerations), but before we get to that, we should resolve to support nested @sheet blocks at all.

[romainmenke]

I think this should be supported.
I don't really see a reason not to allow this.

Imported stylesheets can themselves contain @import statements.

[mirisuzanne]

This makes sense to me, I'm in favor of the syntax as proposed. But I expect most of the complexity comes in answering all the questions about import.

[css-meeting-bot]

The CSS Working Group just discussed [css-cascade-7] @sheet - allow nested @sheet statements?, and agreed to the following:

• RESOLVED: Allow nested @sheet statements and follow the nested layer syntax

The full IRC log of that discussion

<emeyer> kurt: For @sheet, should we allow sheets to be nested? It would be similar to @layer
<emeyer> …They should also be delimited with a period, like with layers
<emeyer> …My proposal is that we allow this for consistency
<TabAtkins> q+
<astearns> ack TabAtkins
<emeyer> TabAtkins: This sounds reasonable; what’s the complexity about @import?
<emeyer> kurt: The behavior of @import in @sheet isn’t well defined yet
<emeyer> TabAtkins: Do you foresee any extra complexity?
<emeyer> kurt: I don’t
<emeyer> astearns: It makes sense to me to follow the layers model
<bramus> +1
<emeyer> astearns: Proposed resolution is to allow nested @sheet statements and follow the nested layer syntax
<emeyer> RESOLVED: Allow nested @sheet statements and follow the nested layer syntax