Generic cosmetic filter doesn't get applied sometimes

[uBlock-user]

I face the issue(cosmetic filter not getting applied from the list) at https://speed.cloudflare.com/, once you complete the speedtest, a filter such as ##.react-share__ShareButton doesn't get applied which is meant to hide the social media buttons on this site.

##.react-share__ShareButton exists in EasyList – Social Widgets.

Occurence is random, so cannot reproduce at will, but once it happens, I force update the list and it goes away for the time being.

This is how it looks like --

@gorhill You said something about :watch-attr(), can you expand upon that ?

[gorhill]

Try *##.react-share__ShareButton and see if this works better.

[uBlock-user]

It works, but are you able to reproduce the issue ? I want to know whats the reason behind this occurence.

[gorhill]

I wasn't able to reproduce, but you said it's random, so given how the page look (dynamically updated), most likely a case of requiring watch-attr -- .i.e. the react-share__ShareButton class is dynamically added after the element had already been surveyed element. Adding a class name or any attribute doesn't trigger the mutation observer, hence doesn't tell the surveyor to re-survey.

[uBlock-user]

Adding a class name or any attribute doesn't trigger the mutation observer,

Is this intentional due to performance issue related to m.o. ?

[gorhill]

Performance, it has been discussed in the issue tracker. There was one issue about a custom cosmetic filter on arstechnica.com suffering such issue, the poster thought it was caused by double dash --, but this was a attribute issue. I am having a hard time to find such old issues lately. I discussed that I was not comfortable with triggering the mutation observer on attribute changes. The solution is either inject uncondtionally (*##), or for procedural operator use :watch-attr operator.