Paragraph rendering in comments is broken

[guillep2k]

• Gitea version (or commit ref): d5b1e6b
• Can you reproduce the bug at https://try.gitea.io:
  • Yes https://try.gitea.io/guillep2k/charset-problem/issues/4

Description

Gitea no longer recognizes paragraphs in a comment, making a single paragraph for all the contents.

I suspect #8560 as the source cause.

Screenshots

This is a three paragraph text:

But it's rendered as a single paragraph:

[InExtremaRes]

It also happens for us in messages in PR, issues, etc. Placing two break lines between paragraphs makes it works. The preview of the message is shown correctly nonetheless.

[zeripath]

@lafriks I suspect this is associated with the move to blackfriday 2.

[tostercx]

Also in wiki :<

[guillep2k]

From some quick tests I did, the problem seems to arise when input comes with \r\n instead of \n (which is not always the case). Removing \r from the input won't trigger the problem.

[guillep2k]

It seems to be tied to this issue at blackfriday, but reporters get inconsistent results: sometimes they need to convert \r\n to \n and sometimes the other way around. I wonder if this is will behave differently when Gitea is running under Linux, Windows, Mac, etc.

[guillep2k]

OK, bad news: it's a problem that's been hanging around in blackfriday/v2 since 2018:

russross/blackfriday#423

No merge in sight.

[InExtremaRes]

[...] Placing two break lines between paragraphs makes it works. [...]

I don't know exactly when this breaks but now placing two or more break lines doesn't work anymore; even PR that looked ok with that trick now are rendered as a single paragraph.

FWIW we are using gitea inside docker with the image gitea/gitea:latest. The host is Debian and the I access through an Archlinux using Chromium.