Omit prelude requirement for SCSS `@else`

[mrtnvh]

Problem

Snippet: https://github.com/csstree/stylelint-validator/blob/v2.0.0/lib/syntax-extension/sass/index.js

is causing the error

At-rule '@else' should contain a prelude (csstree/validator)

with code

  @if ($value == 0) {
    @return 0;
  } @else if ($value == 1) {
    @return 10;
  } @else {
    @return $delta;
  }
}

Analysis

As the else scss at-rule, doesn`t have a prelude, it looked like the simple solution would be:

// /lib/syntax-extension/sass/index.js#L56
syntaxConfig.atrules.else = {
    prelude: null
};

// /test/preprocessors.js#L80

// Add braces to ensure xxx is or is not seen as prelude
tr.ok('@else {}');
// Add missing else if
tr.ok('@else if {}');

But then the tr.ok('@else if {}'); assertion fails with At-rule '@else' should not contain a prelude (csstree/validator).

If we analyse the AST of the first code snippet (available here), the else if at-rule takes everything starting from if as prelude.

What should be the correct configuration for the else and else-if at-rule?

I've already forked the repo and tinkered with, without any success. Can you be of further assistance?