Edge case: property can take coma-separated values

[meduzen]

Considering this:

.my-class {
  transition-property: var(--transition-properties, opacity, visibility)
}

This is not possible to get the same result with v() because it will wrap opacity as custom property name (var(--opacity). In this case, v() shouldn’t be used. See next comment. 🤓

[meduzen]

Actually it’s possible by wrapping them in quotes:

.my-class {
  transition-property: v(transition-properties, 'opacity, visibility')
}

[meduzen]

It turns out the previous example is wrong because it generates:

.my-class {
  transition-property: var(--transition-properties, 'opacity, visibility');
}

As described on MDN (or just before example 12 in the spec), the quotes are not valid.

This should be generated instead:

.my-class {
  transition-property: var(--transition-properties, opacity, visibility);
}

I think there are two futures for this issue:

1. Mark the multiple fallbacks as unsupported.
2. Unquote the fallback parameter in such use cases.

I’d rather give a try at option 2 in order to improve the package.