TL:DR; Page status indicators ( https://www.mediawiki.org/wiki/Help:Page_status_indicators ) require native Parsoid support since the body can have arbitrary wikitext (like <ref>) which should be handled natively. Chat transcript with Bartosz below that explains this.
<subbu> so, are page status indicators an extension?
<MatmaRex> no, it's a core feature of MediaWiki
<MatmaRex> but they're implemented using "extension tag", or "tag hook", like e.g. <gallery>
<subbu> right .. so, i am trying to figure out if parsoid needs custom support for it.
<subbu> or, if will show up as a registered extension and we'll get that handled via the normal extension parse req. to the m/w api.
<subbu> i guess i could try it out. :)
<MatmaRex> seems that it does should up, i didn't even realize, huh.
<MatmaRex> you might want to do something special to treat it as a meta item, though.
<subbu> but, it is not generating any output right now.
<subbu> echo '<indicator name="foo">[[File:Foo.svg|20px]]</indicator>' | node parse
<subbu> <span data-parsoid='{"dsr":[0,55,2,2]}' typeof="mw:Extension/indicator" data-mw='{"name":"indicator","attrs":{"name":"foo"},"body":{"extsrc":"[[File:Foo.svg|20px]]"}}' about="#mwt3">
<subbu> </span>
<subbu> will have to investigate if that is a parsoid bug, or if that is the right output for that indicator
<subbu> do they need special editing support in VE?
<MatmaRex> subbu: i am not as up to date on how VE works as i'd like to be, but as far as i know:
<subbu> offhand, do you have an example page with indicators that I can use to play with this?
<MatmaRex> subbu: indicators should be treated as meta items (like [[category:foo]], etc.), but their contents should be parsed like "subdocuments" (like <ref>, i guess?) and VE should be given the parsed HTML (and the ability to send it back). note that they will likely be usually template-generated
<MatmaRex> let me find one
<MatmaRex> subbu: on this page: https://pl.wikipedia.org/wiki/Zręczyce the coordinates in top-right are generated with <indicator>, somewhere deep in the infobox. (let me find something simpler :) )
<MatmaRex> subbu: simpler example: https://pl.wikipedia.org/wiki/Kwatera_na_Łączce the <indicator> comes from the {{koordynaty|52.255736|N|20.952429|E}} call at the top of the article
<subbu> so, http://parsoid-lb.eqiad.wikimedia.org/plwiki/Zr%C4%99czyce?oldid=42190879 doesn't generate anything. so, looks like we'll need some patches to core to pass back indicator information as part of the api call.
<subbu> otherwise, when they are templated, parsoid will never know about their presence.
<subbu> just like categories, and other resources (css, js).
<MatmaRex> subbu: https://www.mediawiki.org/wiki/Phabricator also has an indicator in top-right
<MatmaRex> subbu: you're using api=expandtempltaes, right?
<subbu> api=parse for this
<MatmaRex> or parse?
<MatmaRex> you can pass api=parse&indicators=1, i think
<subbu> oh, i see.
<MatmaRex> to get… something out. i don't quite remember :P
<subbu> ok .. thanks.
<subbu> MatmaRex, &prop=indicators does it.
<subbu> ex: https://en.wikipedia.org/w/api.php?action=parse&format=json&text=%3Cindicator%20name=%22foo%22%3E[[File:Foo.svg|20px]]%3C/indicator%3E&prop=text|modules|jsconfigvars|categories|indicators
<subbu> MatmaRex, so, can indicator body have arbitrary wikitext?
<MatmaRex> subbu: technically yes
<subbu> hmm ..
<MatmaRex> (although obviously it will start looking very silly pretty fast)
<subbu> so, that is an issue.
<MatmaRex> it probably doesn't need to be arbitrary, there's no reason to put anything block-level there, but it's not easy to limit that in the wikitext parser
<subbu> so, for indicators that are templated, since parsoid doesn't see the actual wikitext, we'll end up mixing php-parser-generated html for wikitext with parsoid-generated html.
<MatmaRex> (we still want links, images, text formatting)
<subbu> over time, they will converge, but, in the interim, editability of indicators will suffer.
<subbu> for top-level indicators, parsoid can implement a native extension for it and not ask php parser for the output.
<subbu> and they can be edited. so, maybe not an issue after all.
<subbu> since only top-level indicators are directly editable .. and templated content can never be.
<MatmaRex> yeah. i think that works out well enough?
<subbu> alright, I think so, we are looking at a native parsoid impl. for this. and rely on the api=parse output for templated indicators.
<MatmaRex> yeah. toplevel indicators are probably rare, i doubt you'll encounter them in the wild, apart from user pages maybe