Trump was in dominant form throughout the match contributing breaks of 131, 55, 65, 82 and 60 to reach his first final at the event.
Donaldson enjoyed runs of 75, 74, 40 and 42. He recovered from trailing 4-1 to 4-3, but Trump was in no mood to suffer another near-miss as he convincingly won the final two frames of the match.
“It was a bit of a struggle today,” said Trump. who is bidding for a seventh ranking title. “I was good at the start and at the end, in the middle I let it slip a little bit, but I managed to hold on and win.
“At the start he was a bit nervous so it was important for me to get a good lead. The crowd started to get behind him, they want to see a close game. It was important for me to be professional and not miss anything easy.
“I had some tremendous support, the crowds all week have been as good as anywhere. Today it was packed out, it had an extra buzz, especially because it is a semi-final.
“It will be tough if I play Stuart tomorrow, it is always close between us, so I will need to play well to win it. Robert is initially from Bristol too, so he will have a lot of support. We play quite a similar game – attacking – so if I play Robert it will be good for the fans.”
Trump’s last tournament win came at the European Masters in October.