does like engine swap require reprogramming?

In simple terms no not normally, if every electrical item is swapped over then no programming will be required.

Even if all the electrical sensors and actuators are replaced then then occasionally you will need to recalibrate the throttle body and fuel trims but theses will adjust over time anyway.

If it is a diesel engine then the injectors should be programmed to the ECU but 90% of the time it isn't strictly needed.

Short answer is no, you will not need to reprogram the ECM.

You can swap engine and sensors over but keep your original ECM, it will work no problem.

Since the ECM would of been without power during the swap, then it will be reset back to default settings and will basically be in learning mode when you power up the engine.

So even though the replacement engine may be slightly different in physical characteristics (depending on injector efficiency etc.) it will not be an issue.

EDIT: I should add, if you have an immobiliser, that will need to be reprogrammed for the new ECM.