The Jedi Path: A Manual for Students of the Force, is a 2010 book by Daniel Wallace which explains the “doppelganger” technique used by Luke Skywalker at the end of The Last Jedi to trick Kylo Ren. Showing that it was part of Star Wars long before The Last Jedi.
https://twitter.com/rianjohnson/status/954398403986731008
I know the book is Legends, but it is part of the Legends series that has made it’s way into the canon. For more information on the book, you can access the Wookieepedia.
And here we have the original post from Rian Johnson in Twitter, showing the book and the information about the “doppelganger” technique. See for yourself.

