Donald, who was the leader after Thursday's opening round, shot a 4-under-par 68 Friday for a 36-hole total of 11-under 133. McIlroy and Warren each had one bogey Friday in turning in 5-under 67s for their shares of the lead.
Brenden Grace opened Friday's play with three consecutive birdies en route to a 7-under 65 and is tied with Louis Oosthuizen (67 Friday) for fourth at 10-under. Charl Schwartzel (67) and Richie Ramsay (68) are in sixth at 9-under 135.
Donald was steady through Friday's play, making birdies at Nos. 1 and 9 on the front while adding two more at 14 and 18, tapping in from 18 inches on the final hole, for a second consecutive bogey-free round.
McIlroy's first bogey of the week came Friday at the par-3 fourth hole while Warren, had a 6 at the par-5 No. 7 hole against his six second-round birdies.
Sergio Garcia posted the best score of the day -- 8-under 64 -- but it was a round in which he had just four pars. All of those came on the front nine, where he also had five birdies. Garcia's second nine featured four birdies and eagles at Nos. 14 and 18 but also bogeys at 12 and 13 and a triple-bogey 7 at the 16th hole. He's at 7-under for the tournament, tied for 18th.