ESLint Demo doesn't show red-line on the error locations

[mysticatea]

I expected the editor to show red wave lines on the error locations and show popups when I hovered the mouse pointer.

[kaicataldo]

Huh, the red wavy lines were working when I switched out the underlying code editor (though maybe they don't show up when it's only highlighting one character?). What browser are you seeing this in?

This is what I see (in latest Firefox):

[mysticatea]

Repro: https://eslint.org/demo#eyJ0ZXh0IjoiLyplc2xpbnQgbm8tZXh0cmEtcGFyZW5zOiBbZXJyb3IsIGFsbCwgeyBlbmZvcmNlRm9yU2VxdWVuY2VFeHByZXNzaW9uczogdHJ1ZSB9XSAqL1xuXG4vL+KclCBHT09EXG5pZiAoKGEsIGIpKSB7fVxuIiwib3B0aW9ucyI6eyJwYXJzZXJPcHRpb25zIjp7ImVjbWFWZXJzaW9uIjo4LCJzb3VyY2VUeXBlIjoibW9kdWxlIiwiZWNtYUZlYXR1cmVzIjp7fX0sInJ1bGVzIjp7fSwiZW52Ijp7fX19

I have reproduced it on Chrome 76, Firefox 69, and Edge 44.

[mdjermanovic]

Does this particular example look a little better now? Seems that the red lines don't want to go much under the parens in Chrome, but at least something is visible now. It looks ok in Firefox.

This was changed in eslint/eslint#12302, it happens when a rule reports only loc.start.

There is an issue eslint/eslint#12334 to fix this in other rules.