Upstream has released updates that appears to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing
Bukkit Changes:
c71bb9ca Add PlayerRecipeDiscoverEvent and methods to (un/)discover recipes
CraftBukkit Changes:
7a2f4867 Implement PlayerRecipeDiscoverEvent and methods to (un/)discover recipes
ForgeFlower is better than Spigots FernFlower at decompiling the source.
However, in order to maintain the CraftBukkit patches, we must keep
using spigots for the primary.
However, for any file that we import on top of Spigots imported files
there is nothing stopping us from using better decompiled files.
So these changes will use ForgeFlower to maintain a better set of
decomped files, so anything we add on top of Paper can start off
in a better spot.