aria-roledescription is empty or whitespace characters
https://w3c.github.io/core-aam/#ariaRoleDescriptionEmptyWhiteSpaceString

Whitespace characters are underspecified here. The Unicode code points should be included in the spec to ensure interoperability.

See CSS Text and WGSL for examples.

Note that we (the i18n WG) are also revising our guidelines for spec editors on defining whitespace characters (in w3c/bp-i18n-specdev#77 ).