It looks like starting in Xcode 13, some error messages now have 'action buttons' that are being used in a few different places to jump to other files or open dialogs. I was wondering if these were powered by sourcekit, or if Xcode is just pattern matching against the message text here? I'd like to explore adding buttons to jump to the docs in the userdocs/ folder from error messages if it's possible to set these up to open an arbitrary file URL. I couldn't find any support related to this in the Swift repo, but thought I'd check just in case it hasn't been upstreamed yet.
The "Search package collections" action, as well as deciding when to offer it, is implemented in Xcode, not in SourceKit.