Delimiters used by other filters are printed, not interpreted

Sorry same thing here, can you provide steps + example markup/content + screenshots where possible? I am volunteering my own time so ideally would have as clear steps as possible so I can focus on providing the functionality you expect. Thanks!

The delimited by @...@ is converted to links to the sources table.

if you compare the HTML source which I pasted at

https://www.drupal.org/project/footnotes/issues/3414604#comment-15397449 🐛 Support adding the text content within the element Fixed with the HTML source of https://www.givewell.org/charities/malaria-consortium you can how the link is grabbed from the Source table at the bottom of the page, and used to turn delimited text into links.

If I understand correctly, in your markup (after 🐛 Support adding the text content within the element Fixed is in) you will have:

<footnotes data-value="">Some text with @https://drupal.org@.<footnotes>

and:

1. you expect the @https://drupal.org@ to be converted to <a href="https://drupal.org">https://drupal.org</a>
2. you are saying 3x supported that conversion
3. you had some way to specify whether the character was @, or #, or something else

Is that correct? So you effectively have your content editors writing some combination of html and custom markdown-ish like thing. I do not see that documented in 3x anywhere, could you point me to where it is? I also tried searching the Filter itself and do not see any reference to that in 3x here.

Seems a bit dangerous to auto-convert anything between two @ signs or two # signs for example. What if the content editor legitimately wants to use those characters. Seems like this is perhaps better moved to ✨ Provide a drush command upgrade path for 3x to 4x to convert from [fn] and to the new modal window Needs work to migrate away from that perhaps?

Converting text between delimiters can cause problems. We do convert text between @...@ using custom code. If it becomes a probem will configure more unusual characters as the delimiters.

This kind of thing is not unusual. Mathjax does it on the frontend to format mathematical notation. There is no documentation indicating whether Footnotes 3.x. supports it. However, it did not break Footnotes 3.x. There are many other situations where HTML which does not comply strictly with the HTML 5 standard works, and is used. CKEditor 5 and Guteberg both use far wilder non-standard HTML than this.

However, it did not break Footnotes 3.x.

And it breaks in 4x? Howabout with the code from 🐛 Support adding the text content within the element Fixed ? Sorry to be a pain - I really need to understand the issue and how to reliably and as easily as possible reproduce it in order to understand how to solve.

We are adding @ as delimiters around text which a filter should process. As it happens, that filter is turning the delimited text into a link.

When our delimited text is added inside <foonotes> tags, our problem clears up. The text delimited by @...@ is converted to a link by our custom filter.

When adding the same text inside the data-text attribute, the @...@ are simply printed to output, and not processed by the filter.

We could use different characters as delimiters, and update all legacy content. I have notg tested using other delimiters.

When our delimited text is added inside tags, our problem clears up. The text delimited by @...@ is converted to a link by our custom filter.

So should this issue be closed then?

When our delimited text is added inside <foonotes> tags, our problem clears up. The text delimited by @...@ is converted to a link by our custom filter.

You could change your custom filter to run earlier. Whether the custom filter runs on a data attribute or not of course depends on your custom filter.