This isn't even a complete list of rappers who also collaborate with other writers on many songs. theres many more of these. its been happening since the beginning of hip hop.

ICE CUBE used several writers

Ray Luv, one of 2 Pac old friends and collaborator reveals he wrote for Pac a lot

one of Future's frequent co-writers Bobby Raps, wrote a couple of songs for him as well. the melodic ones

Throw anyone who reciting full verses from other niggas off #the #lists

damn y’all still talkin??