What I was looking for originally was a way to get more information on certain failed checks, particularly the ones where the extra detail (like which PHP files were found in uploads) won't fit nicely in a shorter-style summary "message".
Oh right. I was thinking these could go in a data field (or something better named). I think it needs to be in a separate field though, because it could be a huge amount of data and probably wouldn't be something you want to try to parse out of a message.
Can you give an example of what would be in the data field for the php-in-upload check? Would it be the file paths separated by newlines?
It would be the file path relative to WordPress root in JSON format. In --format=table, the JSON would be rendered within the table. In --format=json, it would be true JSON.
From discussion in https://github.com/wp-cli/doctor-command/pull/131