With the release of Xcode 8, Apple changed up a few things, including the option to inject code into Xcode at runtime. And with that, plugins as we know them are no more.
However, Apple announced that Xcode 8 now has “official” support for creating editor extensions. There are some limitations (e.g. no UI) yet we’re on the right track (read no hacks required). Even better, given each extension is a macOS app, you can distribute your extensions on the Mac App Store!
In this post by Patrick Balestra describes how to create an extensionthat transforms any closure to use the simpler and cleaner syntax.
Using and Extending the Xcode Source Editor from WWDC 2016.