When I go to https://phabricator.wikimedia.org/ I get a pop-up style modal that with the title Unhandled Exception ("ArgumentCountError") and with this content:
Too few arguments to function PhabricatorEditEngineSubtype::newTagView(), 0 passed in /srv/deployment/phabricator/deployment-cache/revs/61f10999d8837a8c9dbeea12f67b2554daf057ab/phabricator/src/applications/project/view/PhabricatorProjectListView.php on line 92 and exactly 1 expected
Mentioned in SAL (#wikimedia-operations) [2019-09-27T00:53:52Z] <twentyafterfour> hotfixing phabricator fatal exception refs T233998
Ignore me if I have no clue what's going on, but I added another call to this method in https://secure.phabricator.com/D20842, which may need adjustment if you've tweaked it (which I think is what's going on here, per rPHABae334e4589a0413c1eb8a9e8d993e553bfeff478).
(That change is from 5 seconds ago so this would just be something to keep an eye on for the next deployment.)
@epriestley: Thanks for the heads up! Indeed I tweaked the way that subtypes work slightly, to make it more extensible. I'd love it if we could upstream some of that but I don't know how much extensibility you want to allow (given that the subtype class was changed to final, among other things, I think that's not much)
The local hack was to implement custom rendering of the subtype tag on workboards - "deadline" tasks render a due date on workboards and change the color of the tag as the deadline approaches. In order to implement that I needed to pass the viewer down to the subtype and made the subtype class extensible to override the rendering of the tag view.