On our Phabricator installation, we have a bunch of old macros with broken thumbnails. It took me a not-insignificant amount of time to figure out how to regenerate these thumbnails, and I consider myself to be a fairly advanced user.
Basically, these are the steps that I had to follow:
- Used the macro.query API method to search for the name of a macro with a broken thumbnail.
- Copy the filePHID from the response.
- Pass the file PHID to phid.query to get the file's monogram.
- Navigate to /${FILE_PHID}.
- Click on "View Transforms".
- Click the "Regenerate" button next to the "pinboard" transformation.
- (At this point I stumbled into another bug, but I'll file that separately).