I have tested this item ? unsuccessfully on

hmm it do not work here on my end.

I have sample data installed and that added to the "First blog post" your extended read more <hr id="system-readmore" style="width: 1013.75px; word-spacing: 0px;"> after that I can confirm it is broken but the same thing happen with that patch applyed.

@zero-24: Just to make sure: after installing the patch you opened the article again and saved it? because the splitting into intro/fulltext only works on saving the text.

I have tested this item ✅ successfully on 2ae3898

Ah ok thanks for the tip works now. Thanks!

I have tested this item ? unsuccessfully on 2ae3898

changed regex doesn't ignore the additional parameters, it removes them.

After save <hr id="system-readmore" style="width: 1013.75px; word-spacing: 0px;"> will be changed into <hr id="system-readmore" />

When you write ignore, I was expecting that it doesn't matter what kind of additional parameter you add.
When you write delete then this test is successful.

@hans2103: i added your hint to the description.
FYI: Joomla stores intro and full text in separate fields. The system-readmore-tag is created when editing an article to separate the fields again when the article is stored. The tag is never stored or used outside the editor. So any other parameters to this tag should be meaningless.

i have no clue, it works as good before the patch like after. It removes the additional attributes, but isn´t that a wanted function?

I have tested this item ? unsuccessfully on 2ae3898

with and without PR a <hr id="system-readmore" style="width: 1013.75px; word-spacing: 0px;"> changes to <hr id="system-readmore" />

I don't see the issue with that. <hr id="system-readmore" /> doesn't actually get output on a page, it's used internally as a marker to split the introtext and fulltext values. IMO we shouldn't encourage using that specific <hr> as a styling element since the only place you ever see it is the backend editor.

Additional step to see and reproduce the issue #12194 quickly:

Chance the editor to "Editor-None" and save a article for example with insert of:

<hr id="system-readmore" style="width: 1013.75px; word-spacing: 0px;">
to create an introtext.

Show this article on front-end.

I have tested this item ✅ successfully on 2ae3898

@mbabker said that this isn't shown on the page, so what is the use of allowing additional attributes to the readmore tag?

This change really makes no sense at all - why would someone go to the trouble of adding styling to something that is never displayed.

@brianteeman I can not explain how she added the style. It was most likely unintentional, may be with some copy and paste or something like that.
As these styles are not useful and the current behavior (ignoring such a styled hr when splitting the article) is most likely unexpected I suggested this fix to ignore the additional stuff and split the article on the hr.
So the actual question is:
If a user added some style to the hr-tag, for whatever reason, why should joomla not use the styled hr-tag to split the editor content into intro and full text?
If someone know a reason please post here, otherwise it should be save to use the fix.

set Status on "Needs Review".

I don't see a use case/purpose to adding style to the readmore marker. If you have to, then add system-readmore css to custom.css file.

Set to "closed" on behalf of @Quy by The JTracker Application at issues.joomla.org/joomla-cms/12199

Closing for reasons stated above.