Dotted layer name in `@layer` rule throws an error in Less 4.4.0 (regression)

[n3dst4]

To reproduce:

👉️ Playground link 👈️

1. Write a CSS @layer rule in a .less stylesheet addressing a nested layer using dotted notation:

   @layer foo.baz {
      .bar {
          font-weight: bold;
      }
   }

2. Process it:

   npx less stylesheet.less
   

3. Bang:

   Error: [less] at-rule options not recognised

Current behavior:

lessc throws an error on the dotted syntax.

Expected behavior:

The dotted syntax should pass through lessc the same way as a non-dotted rule.

Environment information:

• less version: 4.4.0
• nodejs version: 22.17.0
• operating system: Linux

Other links

MDN Link about nested CSS layers

Playground example of a non-dotted layer name working great in 4.4.0

Playground example of the dotted notation working in 4.3.0

[dosubot]

Hi @n3dst4! I'm Dosu and I’m helping the less.js team.

Less 4.4.0 does not support dotted layer names in the @layer rule. The parser expects a simple identifier and rejects dotted names, which causes the "at-rule options not recognised" error. While support for the @layer rule and layer import syntax was added recently, there is no mention of support for dotted or nested layer names, and no workarounds or plans for this feature are documented or discussed in the codebase or docs [parser source].

At this time, Less will not pass through valid CSS with dotted layer names unmodified. If you need this syntax, you may need to preprocess your CSS or wait for future updates that expand support for the full CSS @layer spec.

To reply, just mention @dosu.

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[puckowski]

@n3dst4 Hello, thank you for reporting the issue. I've prepared a fix in this PR: #4349

[puckowski]

Release PR: #4351