Bug: Filters containing classes with double dashes are ignored

[danielyli]

Describe the issue

Custom filters that specify an element with a class name that contains a double dash (or double underscore) are ignored. This issue is reproducible for any page with an element whose class name contains a double dash or double underscore.

For example, say I want to block the top navigation bar that peeks in on Medium sites when you scroll the site up. My filter is:

##div.metabar--affixed

The filter is ignored.

(Use this Medium article as the test case.)

If I change the filter selector to specify a class without the double dash, the filter works.

Steps for anyone to reproduce the issue

1. Add the filter ##div.metabar--affixed
2. Navigate to https://medium.com/@ageitgey/machine-learning-is-fun-part-4-modern-face-recognition-with-deep-learning-c3cffc121d78.
3. Observe that the filter is not applied (the top navigation bar still creeps in when scrolling up on the site).

Your settings

All settings are default.

• Browser/version: Chrome 52.0.2743.116 (64-bit)
• uBlock Origin version: uBlock Origin v1.8.4

Your filter lists

Default filter lists + the test case specified above

[gwarser]

Works when specific, not visible in log.

[gorhill]

I can't find any element with the class .metabar--affixed on the test page. This is what dev console says:

> document.querySelector('.metabar--affixed');
< null

[gorhill]

Never mind, got it while scrolling up, as you said.

[gorhill]

It's not the double-dash, it's because the class .metabar--affixed is added/removed as one scroll up/down. uBO does not listen to class/id changes in its mutation observer.

In any case, this is not ideal as a cosmetic filter (because it is removed/added dynamically), .metabar--postArticle (or even better because specific filters are always better: medium.com##.metabar--postArticle) works better here, as it is a permanent class on the div.

Edit: Ok, I can see the benefit of using .metabar--affixed, it just prevents the top bar from floating while scrolling, while not getting rid of it completely. I have a fix locally, but I want to better evaluate its impact.

[danielyli]

What's interesting is that on some other sites (e.g., this) uBlock accommodates the dynamic addition of classes:

1. Navigate to this article. The header bar peeks in when scrolling up. With dev tools, we see that scrolled-up is one of the classes dynamically added to the element.
2. Create filter: arstechnica.com##header.site-header.is_stuck.scrolled-up
3. Refresh. The element no longer peeks in when scrolling up.
4. To make a minimal example, change the filter to: arstechnica.com##header.scrolled-up
5. Refresh. The element is blocked when you scroll up.

[gorhill]

Because specific filters are used in your arstechnica.com example. Specific filters (ex. arstechnica.com##header.scrolled-up) are always injected, but generic ones (ex. ##header.scrolled-up) are injected only after uBO's DOM surveyor finds a match. Not watching for class/id changes prevent uBO from finding out whether new generic filters must be injected when a new class or id is merely added to an existing DOM element.

[danielyli]

Ah, I see. Great, thanks for the explanation.

[ryanbr]

I've started to notice a trend of a certain CMS's using the "__" div elements. Given the age of this bug, is going to be fixed?

Was trying to filter on tunein.com "##.footer__socialLink___1Iby-" Even the following didn't work;

tunein.com##div[class*="socialLink"]
tunein.com##div[class^="footer__socialLink"]

[gorhill]

The bug title is incorrect, it has nothing to do with double-dash, or any double-anything.

[gorhill]

tunein.com##[class^="footer__socialSection___"]

or

tunein.com##[class^="footer__socialLink___"]

work fine for me.

[gorhill]

tunein.com##div[class*="socialLink"]
tunein.com##div[class^="footer__socialLink"]

These filters don't work because there is no div with class with socialLink substring in it, there are a elements with class footer__socialLink___1Iby-, and there is a div element with a data-testid attribute set to socialLinksContainer.

[ryanbr]

hmm annoying, right, doesn't show what type of element it is. Is there feature request to show the type of element being used when using the Picker?

[gorhill]

There is #1736, which I interpret as wanting more controls over cosmetic filter crafting.

[gorhill]

By the way, how did you come to create the filter with a div with the element picker? The element picker would have found no match on the page, and in such case it won't let you create the filter.

[gwarser]

One more case I believe: https://www.reddit.com/r/uBlockOrigin/comments/emy5cd/baseballreferencecom_doesnt_load_with_ubo_enabled/

@gorhill, you should change title to something actually describing the issue.

[gorhill]

Listening to class/id changes would affect negatively performance, so such cases have will have to be worked around using either specific cosmetic filters, and specific-generic cosmetic filters will have to be used in case the filter is meant to apply everywhere.