material-ui - JSS issues

[bartlomiejzuber]

When tests are run on components written with makeStyle from https://material-ui.com/ library you will see plenty of those warnings in your console:

I've tracked down this issue through https://github.com/cssinjs/jss and found out the issue occurs if rule isn't valid by e.g. if some property miss the value.

Then cssRule becomes undefined and this error is thrown:

[JSS] Cannot set property 'parentStyleSheet' of undefined

Imo as original insertRule doesn't throw this error for invalid rules it should work the same in CSSOM.

If you need help with fixing it, please let me know. :)