Variable Font Instance set as Undefined

[isaiasloaiza]

When I list a variable font (with its instances) in a webpage using opentype.js, it prints everything as expected except for one instance that is “Undefined”.

MyFont_VF - undefined

As far as I know, this is because in the fvar the Regular version points to the subfamilyNameID=2 and is ignored. The other NameInstances point to a subfamilyName=259 or another.

Our guess is that opentype.js doesn’t handle the “elided fallback name” mechanism correctly.

You can see the screenshots of the problem here:
https://forum.glyphsapp.com/t/variable-font-instance-set-as-undefined/34096/1