thanks for all the details! agreed, this would definitely be fun to have.

updated title since we should ideally do this for all silo person tags, not just on posts published by bridgy.

oh wait sorry, i misread. this is the other direction. reverting that change.

slightly modified since afaik it's not technically photo-specific: you can person-tag arbitrary FB/twitter posts, with or without a photo.

agreed, more than just photos, photos just happen to be key (driving) use-case :)

Also, extended person-tag markup example added as promised: http://indiewebcamp.com/person-tag#With_other_profiles

Inline for your convenience:

<span class="u-category h-card"> 
  <a class="u-url p-name" href="http://ben.thatmustbe.me/">Ben Roberts</a> 
  (<a class="u-url" href="https://twitter.com/dissolve333">t</a>, 
   <a class="u-url" href="https://www.facebook.com/dissolve333">f</a>)
</span> 

turns out this a dupe of #318, but it has useful details, so i'm closing #318 instead.

And on the backfeed side: #488

current silo support:

• Facebook: yes. POST to /user/feed and set the tags param to a comma separated list of FB user ids. needs the user_friends permission and maybe the Taggable Friends API. Details.
• Flickr: yes. using the photos.people.add endpoint. we'd need to do Flickr publish support #432 (publish support) first though.
• Twitter: no. they're called photo or people tags. nothing in the uploading media or statuses/update docs, doc searches, or forum searches or posts.
• Instagram: no, since the API is mostly read only. you can't post pictures or tags.
• Google+: no, since the API is read only.

facebook is done! tested just now and it works. silo SWAT0 here we come!

flick is done now too, thanks @kylewm!

tentatively closing this since the other three silos aren't possible. if anyone badly wants this for the other silos and really wants to track it in case they add support in the future, feel free to reopen.

Agreed with closure as completion of what's possible today. Other silos should be separate issues with proposals that are either actionable today or fully "wish list" awaiting something from the silo.

Looks like this may have broken recently in Bridgy Publish photos + person-tags to Facebook at least.

This post: http://tantek.com/2016/018/t4/w3cab-meeting-hawaii (has a bunch of person-tags)
Bridgy Publish POSSE to Facebook copy: https://www.facebook.com/photo.php?fbid=10102083967065093

Note that none of the person-tags (including my tagging myself) made it to the POSSE copy on Facebook.

All of the person-tags on that Facebook copy (including of me) were added afterwards by Coralie, as you can see by hovering over the person-tags and looking the top left of the resulting pop-up where it says in small white text "Tagged by Coralie Mercier".

Any idea what broke? Re-open this?

For reference, we originally noticed that person tags seemed to work when you use the person's numeric ID as their URL in http://tantek.com/2015/350/t2/seasons-greetings-homebrew-website-club where it successfully tagged Marc Canter, even though he has never logged in to Bridgy. But even if that was a fluke, we still would've expected Tantek's person tag of himself to make it through.

I mentioned on IRC that person tags used to not work without a location ("You cannot specify this field without also specifying a place.", though the same caveat does not exist on the photos page) and I was surprised when they started working. Maybe Facebook fixed the "bug" that was letting us do it temporarily.

here's the publish log.

from IRC:

snarfed looking at the log, this is what we sent to facebook:
snarfed url=https://scontent-sjc2-1.cdninstagram.com/hphotos-xtf1/t51.2885-15/e35/12407429_887813537998827_121176936_n.jpg&message=One week ago, @W3CAB meeting in #Hawaii. I blame @Nov_Project for the #straightface reflex. #latergram #nofilter\n\n(Originally published at: http://tantek.com/2016/018/t4/w3cab-meeting-hawaii)&tags=[{"tag_uid": "100000802747500"}, {"tag_uid": "735170173"}, {"tag_uid": "214611"}, {"tag_uid": "538464812"}, {"tag_uid": "692216758"}]
snarfed so that included five person tags
snarfed so evidently FB rejected them all?
snarfed (we can load those user ids' profiles to confirm that they're the right people)
kylewm well 214611 is definitely tantek

the tags param format with url-encoded JSON seems odd, but evidently it's right. e.g. this older FB publish with successful person tags used the same format:

url=https://i1.wp.com/snarfed.org/w/wp-content/uploads/2015/11/wpid-wp-1447899561388.jpg?w=696
  &message=Celebrating Homebrew Website Club\xe2\x80\x99s 2nd anniversary....
  &tags=[{"tag_uid": "36802236"}, {"tag_uid": "214611"}]

the FB API call is a POST to /USERID/photos, and its docs confirm this format. StackOverflow too.

plus, we got a 200 from the API request, and FB usually returns non-2xx with error details if we give it a bad parameter; it doesn't usually silently ignore.

tantek's access token includes the publish_actions permission, which should be enough.

i don't have any new leads on this, and i haven't found any other recent person-tagged facebook publish attempts to compare against. :/ @tantek, definitely let us know if you end up trying again!

@tantek retried and person tags went through again, surprisingly even more than we thought. details:
#568 (comment)

we still don't understand why tags didn't work the last time, but it's looking like our code is working naively at least, and Facebook's tagging API is either unpredictable or more complicated than we thought.

so, I'm tentatively (re)closing this. we can keep collecting data points on the complexities in #568.