[css-nesting] keeping track of what can and can not be nested

[romainmenke]

Nesting is a high maintenance feature for tooling (transpilers, linters, ...) and code editors.

With each new at-rule that can be nested these tools need to be updated to specifically allow both declarations and style rules.

This is different from before where allowing only style rules was a sane default for unknown at-rules.

It would be helpful if there was an authoritative and exhaustive list of all at-rules that are allowed in nesting so that maintainers do not have to read every single specification to gather the complete list.

example :
css-transitions-2 introduces @starting-style which can be nested : https://drafts.csswg.org/css-transitions-2/#example-8d9992e9

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I think it would even be reasonable if only css-nesting defines which at-rules can be nested.

[romainmenke]

Alternatively making it possible to scrape this aspect so that it can be part of something like webref would also help.

[cdoublev]

Alternatively making it possible to scrape this aspect so that it can be part of something like webref would also help.

I would be interested too. Rule definition tables may be more appropriate than production rules:

      Name:  foo
   Prelude:  <prelude>
     Block:  <block-contents>
Properties:  list of accepted/excluded properties
     Rules:  list of accepted/excluded rules
   Cascade:  yes, ... (optional - but conventional - prose)

New CSS rules (or updates to the above features) are rare, though.

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I think it would even be reasonable if only css-nesting defines which at-rules can be nested.

This list in CSS Nesting (2.2. Nesting Other At-Rules) may need to be updated:

Specifically, these rules are capable of being nested group rules:

• all the conditional group rules (@media, @supports)
• @layer
• @scope
• @container