AP: try marking up @-mentions in content with semantic HTML

[snarfed]

Mastodon understands which links in a given post are @-mentions and rewrites them to point to the local instance. Example: https://ohai.social/@lutoma/111947244364291173 . The first reply there from me is via Bridgy Fed, which has @-mention links that don't get that rewriting.

The only differences I see between the two posts' AS2 is that Mastodon's tag.names are fuly qualified, eg @mmu_man@m.g3l.org, while BF's are only @mmu_man, and that Mastodon's a tags in content have class="u-url mention". Not sure which matters, or both, or something else:

Mastodon AS2 object:

{
  "type": "Note",
  "id": "https://ohai.social/users/lutoma/statuses/111947244364291173",
  "url": "https://ohai.social/@lutoma/111947244364291173",
  "inReplyTo": "https://m.g3l.org/users/mmu_man/statuses/111947239114557378",
  "published": "2024-02-17T14:16:27Z",
  "attributedTo": "https://ohai.social/users/lutoma",
  "to": ["https://www.w3.org/ns/activitystreams#Public"]
  "cc": [
    "https://ohai.social/users/lutoma/followers",
    "https://m.g3l.org/users/mmu_man",
    "https://abyssdomain.expert/users/filippo"
  ],
  "content": "<p><span class=\"h-card\" translate=\"no\"><a href=\"https://m.g3l.org/@mmu_man\" class=\"u-url mention\">@<span>mmu_man</span></a></span> <span class=\"h-card\" translate=\"no\"><a href=\"https://abyssdomain.expert/@filippo\" class=\"u-url mention\">@<span>filippo</span></a></span> social.vivaldi.net is run by a for-profit entity. There&#39;s probably a few other ones as well.</p>",
  "tag": [{
      "type": "Mention",
      "href": "https://m.g3l.org/users/mmu_man",
      "name": "@mmu_man@m.g3l.org"
    }, {
      "type": "Mention",
      "href": "https://abyssdomain.expert/users/filippo",
      "name": "@filippo@abyssdomain.expert"
    }],
  "..."
}

BF AS2 object:

{
   "@context" : "https://www.w3.org/ns/activitystreams",
   "type" : "Note",
   "id" : "https://fed.brid.gy/r/https://snarfed.org/2024-02-18_lutoma-ohai-mmu_man-filippo-social-vival-ohai-social",
   "url" : "https://fed.brid.gy/r/https://snarfed.org/2024-02-18_lutoma-ohai-mmu_man-filippo-social-vival-ohai-social"
   "attributedTo" : "https://fed.brid.gy/snarfed.org",
   "to" : ["https://www.w3.org/ns/activitystreams#Public"],
   "cc" : [
      "https://abyssdomain.expert/@filippo",
      "https://m.g3l.org/@mmu_man"
   ],
   "content" : "<a class=\"u-in-reply-to\" href=\"https://ohai.social/@lutoma/111947244364291173\"></a>\n<div class=\"e-content\">\n<a href=\"https://abyssdomain.expert/@filippo\">@filippo</a> <a href=\"https://m.g3l.org/@mmu_man\">@mmu_man</a>\n<p>Yup, many. <a href=\"https://me.dm/\">me.dm</a>, <a href=\"https://flipboard.social/\">flipboard.social</a> and soon <a href=\"https://flipboard.com/\">flipboard.com</a>, <a href=\"https://1password.social/\">1password.social</a>, <a href=\"https://dnsimple.social\">dnsimple.social</a>, among others.</p>\n</div>",
   "inReplyTo" : "https://ohai.social/@lutoma/111947244364291173",
   "published" : "2024-02-18T10:05:50-08:00",
   "tag" : [{
         "href" : "https://abyssdomain.expert/@filippo",
         "name" : "@filippo",
         "type" : "Mention"
      }, {
         "href" : "https://m.g3l.org/@mmu_man",
         "name" : "@mmu_man",
         "type" : "Mention"
      }],
}

[snarfed]

Got nudged on this again recently: #1009 (comment)

[Tamschi]

[I removed my earlier comment, that was mistaken.]

Ah, actually I think it finds them by CSS class, here: https://github.com/mastodon/mastodon/blob/b06fd54c305915527e3a6edc575dc23b623143ef/app/javascript/hooks/useLinks.ts#L8-L9C31.
The mention class is allow-listed in the HTML sanitiser here: https://github.com/mastodon/mastodon/blob/b06fd54c305915527e3a6edc575dc23b623143ef/lib/sanitize_ext/sanitize_config.rb#L32

So most likely, you just need to put class="mention" on that <a> tag.

[snarfed]

😂 😭

Thanks for the sleuthing!

[snarfed]

Sadly class="mention" didn't work. Example post:

curl -vL -H 'Accept: application/activity+json' https://bsky.brid.gy/r/https://bsky.app/profile/did:plc:3ljmtyyjqcjee2kpewgsifvb/post/3lacg74pbtb24

eg https://indieweb.social/@snarfed.bsky.social@bsky.brid.gy/113437538777283822 , or if you're not logged into indieweb.social, search for @snarfed.bsky.social@bsky.brid.gy, it's their first post:

[Tamschi]

It's close though, it now fails this condition somehow: https://github.com/mastodon/mastodon/blob/d482211aa6293f78f161cbc7149e829966cd8e3a/app/javascript/mastodon/components/status_content.jsx#L108
(The unhandled-link class that gets added made this easy to search for.)

I had to look this up by searching for https://bsky.brid.gy/r/https://bsky.app/profile/did:plc:3ljmtyyjqcjee2kpewgsifvb/post/3lacg74pbtb24, since Mastodon doesn't backfill and other software can't backfill without the outbox. For reference, this is the JSON:

(I can't copy this as text properly.)

…

Ohhhhhhh.

It matches the link's href on the account's (web) url property, so it probably expects https://mastodon.social/@snarfed rather than the id https://mastodon.social/users/snarfed in the anchor tag!

That actually makes complete sense, since the post body link is user-facing and should point to an HTML page.

[Tamschi]

Regarding my earlier comment #887 (comment): Turns out the function that detects class="mention" is used only in the account bio: https://github.com/mastodon/mastodon/blob/d482211aa6293f78f161cbc7149e829966cd8e3a/app/javascript/mastodon/components/account_bio.tsx#L7

I think this is different because the lookup is lazy there, because Mastodon doesn't want to eagerly fetch a potentially unbounded network of users that bio-mention each other. Accounts tag-Mentioned in Notes are resolved eagerly though, so there it has it on hand more directly.

[snarfed]

Phew. Fediverse hashtags and mentions, ugh, feels like they never end. OK! So the next thing to try here is:

It matches the link's href on the account's (web) url property, so it probably expects https://mastodon.social/@snarfed rather than the id https://mastodon.social/users/snarfed in the anchor tag!

Thanks @Tamschi! BF isn't set up to do this easily right now, not sure how I'd try. Maybe here, load all the mentioned actors, replace their ids in the tags with their urls, run link_tags, then swap the tags back to ids. Heavy, but doable.

bridgy-fed/activitypub.py

Line 856 in fe16b19

as2.link_tags(obj_or_activity)